Symposium Organizers
Graham Cross Trinity College
Andre Schirmeisen University of Muenster
Armin Knoll IBM Research-Zurich
Marco Rolandi University of Washington
FF1: Nanoimprint Fabrication Methods
Session Chairs
Graham Cross
Clivia Sotomayor Torres
Monday PM, November 28, 2011
Room 202 (Hynes)
9:30 AM - FF1.1
Deterministic Fabrication of Hierarchically Ordered, Monolithic Nanotextures by Directional Photofluidization Lithography and Example of Its Use in Superhydrophobic Surfaces.
Hong Suk Kang 1 , Seungwoo Lee 1 , Jung-Ki Park 1 2
1 Graduate school of EEWS, KAIST, Daejeon Korea (the Republic of), 2 Department of Chemical and Biomolecular Engineering, KAIST, Daejeon Korea (the Republic of)
Show AbstractOver the last decade, the fabrication of hierarchically ordered, monolithic nanotextures have attracted a great interest due to its promising application such as advanced photonics and interface sciences. Even if many impressive results have been achieved, most of established methods still suffer from several drawbacks including low throughput, inherently having defects, and multistep process. Herein, to overcome such limitations, we have suggested a new strategy for the generation of hierarchically ordered, monolithic nanotextured surfaces by directional photofluidization lithography (DPL).[1-6] DPL enable the fabrication of a variety of nanostructural motifs with precisely controlled structural features in a very unique way. The key of DPL is to use the photo-reconfigurable polymer (i.e., azopolymer) arrays instead of a conventional colloidal nanosphere, photoresist arrays, and polydimethylsiloxane (PDMS) arrays. By taking advantages of DPL, the structural features of hierarchically ordered nanotexture (i.e., shapes and modulation heights) could be precisely and simply tuned by adjusting the beam variables including polarization, irradiation time, and incident angle. Furthermore, in a more practical point of view, this method also can provide an effective tool for the control of the wettability due to its advantage of simple and deterministic tuning of the structural features. Besides the fabrication of diverse hierarchically ordered, monolithic nanotextures, we believe that this clever experimental strategy and resulting phenomenological finding can give us an important experimental clue for the better understanding of underlying mechanism of surface relief gratings formation onto photo-reconfigurable azopolymer film, which has been a long-lasting question. Therefore, this work can beat the limitation of our current understanding about photo-induced azopolymer movement during light irradiation and, in turn, will greatly extend our ability to fabricate diverse nanotextured structures.Reference1)Lee, S.; Shin, J.; Kang, H.S.; Lee, Y.-H.; Park, J.-K. Adv. Mater. 2011, DOI: 10.1002/adma.201100662.;2)Lee, S.; Kang, H.S.; Park, J.-K. Adv. Funct. Mater. 2011, 21, 1770. 3)Lee, S.; Shin, J.; Lee, Y.-H.; Park, J.-K. ACS Nano 2010, 4, 7175. 4)Lee, S.; Shin, J.; Lee, Y.-H.; Fan, S.; Park, J.-K. Nano Lett. 2010, 10, 296. 5)Lee, S.; Jeong, Y.-C.; Park, J.-K. Appl. Phys. Lett. 2008, 93, 031912. 6)Lee, S.; Jeong, Y.-C.; Park, J.-K. Opt. Express 2007, 15, 14550.
9:45 AM - FF1.2
A Thin Film Transistor on Poly(Ethylene Naphthalate) Foil Using Step-and-Flash Imprint Lithography.
Pieter Moonen 1 , Boris Vratzov 2 , Wiljan Smaal 3 , Gerwin Gelinck 3 , Erwin Meinders 3 , Jurriaan Huskens 1
1 Molecular Nanofabrication, University of Twente, Enschede Netherlands, 2 , NT&D - Nanotechnology and Devices, Aachen Germany, 3 , Holst Centre / TNO, Eindhoven Netherlands
Show AbstractAdvanced and flexible organic electronic devices demand high resolution patterning techniques that, for the sake of low-cost fabrication, can be integrated in high throughput manufacturing lines like roll-to-roll (R2R) assemblies. The low-cost, alternative lithography technique nanoimprint lithography (NIL) [1] provides high resolution patterning combined with short process times. The enhanced functionality of flexible electronic devices (bendable, rollable) combined with low-weight and possible transparency, enables integration into products such as thin-film-transistor (TFT) displays. However, the surface flatness and dimensional stability of the flexible substrates needs to be well controlled to obtain good registration accuracy for multi-layer devices, like TFTs. A new thermal imprinting technique, double layer NIL [2], has been developed to imprint multi-dimensional structures from the sub-micron to millimeter regime. It compensates the inhomogeneous residual layer thickness arising from the wavy foils by depositing resist on mold and substrate. Double layer NIL offers the unique capability of combining two heterogeneous resists with, for example, different surface energy to control wetting.In this paper, the fabrication of flexible TFTs on poly(ethylene naphthalate) foil in a bottom gate, bottom contact architecture is reported (Figure 1). All functional metal – insulator – metal layers were patterned by step-and-flash imprint lithography [3] on foil, allowing sub-micrometer alignment of the source-drain electrodes to the gate. The foils have been reversibly glued to a carrier to enhance the dimensional stability during imprinting. Flexible TFTs with channel lengths from five micron down to the sub-micrometer regime have been fabricated on PEN foil (Figure 2). The semiconductor has been deposited as a blend of TIPS pentacene and polystyrene by inkjet printing [4]. Technology challenges like overlay accuracies, dimensional stability of the flexible substrates and pattern fidelity will be addressed as well.In the future, the here developed SFIL process for the fabrication of flexible TFTs is to be further developed, allowing self-aligned patterning of the source and drain electrodes in respect to the gate, making alignment steps obsolete. The final aim is the integration into a R2R assembly, to fabricate low cost, high throughput flexible electronic devices.[1]H. Schift, J. Vac. Sci. Technol. B 2008, 26, 458-480.[2]P. F. Moonen, I. Yakimets, M. Peter, E. R. Meinders, J. Huskens, ACS Appl. Mater. Interfaces 2011, 3, 1041-1048. [3]P. Ruchhoeft, M. Colburn, B. Choi, H. Nounu, S. Johnson, T. Bailey, S. Damle, M. Stewart, J. Ekerdt, S. V. Sreenivasan, J. C. Wolfe, C. G. Willson, J. Vac. Sci. Technol. B 1999, 17, 2965-2969.[4]X. Li, W. T. T. Smaal, C. Kjellander, B. van der Putten, K. Gualandris, E. C. P. Smits, J. Anthony, D. J. Broer, P. W. M. Blom, J. Genoe, G. Gelinck, Org. Electron. 2011, 12, 1319-1327.
10:00 AM - **FF1.3
Nano-Crossbar Circuits Fabricated Using Nanoimprint Lithography.
Wei Wu 1 , Robert Walmsley 1 , Qiangfei Xia 1 , Jianhua Yang 1 , Max Zhang 1 , William Tong 1 , Warren Robinett 1 , Wen-di Li 1 , Gilberto Medeiros-Ribeiro 1 , Shih-Yuan Wang 1 , R. Stanley Williams 1
1 HP labs, Hewlett-Packard, Palo Alto, California, United States
Show AbstractSemiconductor industry has enjoyed great successes by following the “Moore’s law” for more than four decades. With the end of the roadmap looming in the horizon, great efforts have been made to look for the alternatives for “post-Si” electronics. Transition oxide based electronics (i.e. memristor) is one of the most promising candidates. Memristor is a type of resistive RAM device. It stores the information by ion movements inside the switching material, instead of charge trapping as in other conventional memory devices. I will present our work on memristor nano-crossbar circuits fabricated using nanoimprint lithography (NIL). We have fabricated several generations of nano-crossbar memory circuits, with record-high densities, and have also successfully integrated memristor and Si CMOS circuits. The key enabling technology is NIL. It is a cost-effective nano-patterning technology based on the mechanical deformation of a resist. At HP labs, we have not only designed and constructed five generations of nanoimprinters, but also invented several relating technologies to improve NIL. The latest nanoimprint machine, which is capable of both high-resolution patterning and overlay alignment, will be highlighted in the presentation too.
10:30 AM - FF1.4
Roll-to-Roll Nanoimprinting Metamaterials.
Anton Greenwald 1 , Jae Ryu 1 , Yisi Liu 1 , Rana Biswas 3 , Myung-Gyu Kang 4 , L. Guo 2
1 , Agiltron, Inc., Woburn, Massachusetts, United States, 3 Microelectronics Research Center, Iowa State University, Ames, Iowa, United States, 4 Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 2 Electrical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractWe investigated continuous fabrication of large area 2-D metamaterial comprising a metal dot array on a dielectric coated substrate. We demonstrated patterning of metal dots arrays of varying patterns and shapes with diameter of about 2.5 µm and metal-to-metal spacing from 0.5 to 2.5 µm using a nano-imprinting stamp on a roller. The pattern was first fabricated on a standard photolithography mask, reproduced onto a silicon wafer master mold, and then transferred to a flexible polymer mold that was wrapped around a metal roller. The method was used to pattern a thin Al layer on top of SiO2 on a flexible polymer substrate. The aluminum was coated with a resist and the roller moved over the substrate with adjustable speed and pressure to imprint the fine pattern into the resist. The resist was cured, and a very thin layer of residual resist was removed by RIE, followed by a standard etching treatment for patterning the aluminum layer. Resist was left on some samples to test it as protection for the thin metal. The as-etched pattern had very few defects and the optical properties of the metamaterial were excellent and correlated well with simulations. Design calculations were performed with both commercial and custom software. Our achieved objective was to show that we could vary the resonance from a narrow, sharp absorption spike with FWHM 0.5µm for a central wavelength of 7 µm to a broad absorption peak with FWHM greater than 4 µm for a central wavelength of 10 µm. Infrared reflectance spectra were measured by an FTIR at different angles with or without the polymer resist coating. The coating had little effect optically and could be used to protect the thin metal film. This work has shown that low cost, rapid roll-to-roll processing of 2-D metamaterial structures is possible.This effort was partially supported by the Naval Surface Warfare Center contract No. N00178-11-C-1015 and by the Air Force Research Laboratory contract FA9551-11-C-0033.
10:45 AM - FF1.5
Nanoimprinting with Amorphous Metals.
Golden Kumar 1 , Jan Schroers 1
1 , Yale University, New Haven, Connecticut, United States
Show AbstractThe random structure in amorphous metals (AM) is homogeneous down to the atomic length scale and results in highest strength and hardness, combined with other attractive properties for a structural material. Even more unique is the softening behavior of AM; they can be considered high strength metals that can be processed like plastics. Recently, we showed that some AM can massively replicate features as small as ~10 nm through direct embossing by utilizing favorable wetting conditions between the AM and the mold material[1]. The unique softening behavior in combination with a wider range of softening temperatures, which span a range of 50C-500C among AM provides a versatile toolbox for nanoimprinting. This includes the ability to use AM as a hard mold or, alternatively, a soft imprint material. This toolbox can be used for example in nanoimprint lithography where the robust AM would replace the fragile Si mold in the imprinting process. The low softening temperature of AM and the associate low strength permits to directly write onto the AM as in nano probe lithography. Furthermore, the ability to erase multiple times (103-104 times) features through the action of the surface tension alone before crystallization sets in[2], can be combined with direct writing and used for high density data storage. 1.G. Kumar, H.X. Tang, and J. Schroers, Nanomoulding with amorphous metals. Nature, 2009. 457(7231): p. 868.2.G. Kumar and J. Schroers, Write and erase mechanisms for bulk metallic glass. Applied Physics Letters, 2008. 92(3): p. 461.
11:30 AM - **FF1.6
Development of Nanometrology Methods for Nanopatterning and Self-Assembly.
Clivia Sotomayor Torres 1 3 4 , Timothy Kehoe 1 , Nikolaos Kehagias 2
1 Phononic and Photonic Nanostructures, Catalan Institute of Nanotechnology, Bellaterra Spain, 3 , Institució Catalana de Recerca i Estudis Avançats (ICREA), , Barcelona Spain, 4 Dept. of Physics, UAB, Barcelona Spain, 2 Nanofabrication Division, Catalan Institute of Nanotechnology, (Bellaterra) Barcelona Spain
Show AbstractOne of the major research needs to enable the transfer of novel nanomaterials and nanodevices to end users is in the field of nanometrology methods compatible with a production environment, capable of sub 20 nm feature size resolution in the first instance and eventually capable of chemical and biological metrology.We will address issues of tracebility and methods to establish metrology methods in the nanoscale that will assist in setting standards to enable comparison and reliability studies of nanostrutcures.We will discuss in particular two methods: sub-wavelength optical diffraction applied to nanoimprinted materials and image analysis for ordering in self assembled arrays of nanoparticles.Furthermore, we will discuss emerging methods based on acoustic phonons for sub-5 nm dimensional metrology.
12:00 PM - FF1.7
Continuous Patterning of Nanogratings by Nanochannel-Guided Lithography on Liquid Resists.
Jong G. Ok 1 , Hui Joon Park 2 , Moon Kyu Kwak 3 , Carlos Pina-Hernandez 3 , Se Hyun Ahn 1 , L. Jay Guo 2 3
1 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractNanoscale grating structures have drawn significant research interest as they can be utilized in various practical devices such as optics, displays, and biosensors. In particular, the new Dynamic Nanoinscribing (DNI) can create seamless large-area nanograting structures at high speed [1]. DNI uses a slice of rigid (e.g., Si) grating mold to mechanically inscribe a solid metal or polymer surface at ambient or heated conditions to create nanostructures. However, the elastic recovery of the plastically deformed solid surfaces after the release of mechanical force limits the aspect ratio of the inscribed structure, especially for small period gratings. This cannot satisfy the need for many applications such as metal wire-grid polarizers where higher aspect-ratio and well-defined cross-sectional profiles are highly desirable.To address these issues, we have developed a nanopatterning technique by adopting liquid resist materials to a high-throughput nanoinscribing process, aiming to achieve high-speed and low-cost fabrication of continuous nanograting structures for large-area optoelectronic applications. Whereas a relatively large force is required to ‘inscribe’ nanopatterns on a solid substrate by plastically deforming the material, a liquid resist can readily ‘infiltrate’ the openings in the mold grating upon contact under slight mechanical force. These nanochannel-guided liquid streaks are continuously extruded from the contact region as the mold moves along the substrate surface. We used UV-curable epoxy-silsesquioxane (SSQ) [2], a viscous liquid polymer that can be cross-linked to form high-modulus material upon UV curing in this process, which enables continuous formation of nanograting patterns without elastic recovery. To ensure the success of the nanopatterning process by this “NanoChannel-guided Lithography (NCL)”, the substrate material should have non-wetting property with respect to the liquid resist used in the process. The shallow but plastically deformed groove features on the substrate along with its non-wetting characteristics prevent the immediate reflow of the as-formed liquid nanograting structures until the pattern is fully cured by UV light. The final nanograting geometry can be readily tuned by the substrate surface modification that adjusts its non-wetting property to the liquid resist, and also by the processing temperature that controls the viscosity of the liquid resist and therefore the nanochannel filling height during the process.Such a ‘direct-write’ NCL patterning of liquid resists is a gentler process than the previous DNI technique and result in much more faithful pattern replication for small period and high aspect ratio structures. This new technique may open a way to mass-produce large-area, high-quality nanogratings at low cost.[1] S.-H. Ahn and L. J. Guo, Nano Lett. 9, 4392-4397, 2009.[2] C. Pina-Hernandez, L. J. Guo, and P.-F. Fu, ACS Nano 4, 4776–4784, 2010.
12:15 PM - FF1.8
Nanoimprint Lithography of PS-PDMS Block Copolymers for Extreme Resolution Nanofabrication.
Brett Helms 1 , Vincent Voet 1 , Teresa Pick 1 , Sang-Min Park 1 , Deirdre Olynick 1
1 The Molecular Foundry, Lawrence Berkeley national Laboratory, Berkeley, California, United States
Show AbstractBlock copolymer (BCP) lithography is a powerful technique to write periodic arrays of nanoscale features into substrates at exceptionally high densities. In order to place these features at will on substrates, nanoimprint offers a deceptively clear path toward high throughput production: nanoimprint molds are reusable, promote graphoepitaxial alignment of BCP microdomains within their topography, and are efficiently aligned with respect to the substrate using interferometry. Unfortunately, when thin films of BCPs are subjected to thermal nanoimprint, there is an overwhelming degree of adhesion at the mold−polymer interface, which compromises the entire process. Here we report the synthesis of additives to mitigate adhesion based on either PS or PDMS with short, interface-active fluoroalkyl chains. When blended with PS-b-PDMS BCPs and subjected to a thermal nanoimprint, fluoroalkyl-modified PS in particular is observed to substantially reduce film adhesion to the mold, resulting in a nearly defect-free nanoimprint. Subsequent lithographic procedures revealed excellent graphoepitaxial alignment of sub-10 nm BCP microdomains, a critical step toward lower-cost, high-throughput nanofabrication.
12:30 PM - FF1.9
Microcontact Printing of Self-Assembled Chitin Nanofibers.
Chao Zhong 1 , Adnan Kapetanovic 1 , Yingxin Deng 1 , Marco Rolandi 1
1 , University of Washington, seattle, Seattle, Washington, United States
Show AbstractChitin is an ideal biopolymer for fabrication of biocompatible devices. It is naturally abundant, and has many appealing properties including high mechanical strength, biocompatibility, biodegradability and anti-microbial properties. In nature, chitin is often weaved into well-ordered fibril bundles or arrays. However, integration of chitin nanofibers at the micro and nanoscale is a difficult task because of chitin poor solubility. In our previous work, we have developed a bottom-up approach for producing self-assembled chitin nanofibers (3nm) from hexafluoro 2-propanol (HFIP) solution. Here, we integrate the simple self-assembly strategy with microcontact printing. Patterned self-assembled chitin nanofiber structures with sub 100 nm features are achieved. Chitin self-assembly in the confined environment of the elastomeric stamp is concentration, aging time and geometry dependent. As a result, these factors can be used to control both the direction and geometry of the resulting nanofiber-based structures.
12:45 PM - FF1.10
Chemical and Rheological Control over Hybrid Silica Coatings during Nanoimprint: Application for Light Extraction.
Alban Letailleur 1 2 3 , Cedric Boissiere 2 , Francois Ribot 2 , Clement Sanchez 2 , Jeremie Teisseire 1 , Etienne Barthel 1 , Elin Sondergard 1 , Christophe Couteau 3 , Gilles Lerondel 3 , Nicolas Chemin 4
1 Surface du Verre et Interfaces, Saint-Gobain Recherche - CNRS, Aubervilliers France, 2 Chimie de la Matière Condensée de Paris, Collège de France - Université Pierre et Marie Curie, Paris France, 3 ICD - Laboratoire de Nanotechnologies et d'Instrumentation Optique, Université de Technologies de troyes, Troyes France, 4 Composites and Coatings, Saint-Gobain Recherche, Aubervilliers France
Show AbstractIn light emitting devices, a large amount of the light produced by the active layer is trapped inside the device because of internal reflection. Patterning the different interfaces induces an index gradient and light scattering and can therefore lead to an increase of the light output. Among the existing methods, Nanoimprint Lithography (NIL) emerges as a simple route for surface patterning at the sub-micrometer scale over large areas. To avoid multiple step processing and the poor stability of polymers resins, imprint of functional materials is required.Hybrid sol-gel materials form an innovative class of resists for NIL. They are based on the solution processing of organic precursors to obtain metal oxide. For instance we previously demonstrated the replication of patterns with sub-100 nm lateral size and aspect ratio greater than 1 into hybrids sol-gel silica, using low temperature processing. Fully inorganic silica structures can be obtained after thermal annealing (1). Due to their low dielectric constant, nanopatterned silica coatings are very suitable for applications in photonics, and integration in displays.To achieve high resolution in nanoimprinting, it is crucial to understand the rheological properties of these new resists. Using a combination of dynamic mechanical and electric analysis, we demonstrate that these silicates exhibit a glass transition below room temperature and that the fast increase of this Tg leads to the vitrification and provides long-term stability to the coating. In terms of material structure, we further demonstrate by Infrared spectroscopy that the vitrification is connected to a condensation threshold. (2) This combination of low viscosity and high reactivity enables fast and conformal imprint over several tens of cm2. Furthermore, we demonstrate how the initial material viscosity can be adjusted by changing the elaboration chemistry and how the cavity filling is modified in the imprint process.(3) Finally, we used the solution processing to introduce colloidal quantum dots inside the silica layer, and successfully imprinted the resulting layer.(4) These systems are suitable for light conversion and extraction. As it absorbs around 400 nm and emits light in the visible range, such a layer can act as a conversion layer in LED devices. Furthermore, the light output in the patterned area increased 60 % compared to the flat surfaces.References: 1) Peroz, C.; Chauveau, V.; Barthel, E.; Sondergard, E. Advanced materials 2009, 21, 5552) Letailleur, A.; Teisseire, J.; Chemin, N.; Barthel, E.; Sondergard, E. Chem. Mater. 2010, 22, 31433) A. A. Letailleur, F. Ribot,, C. Boissière, C. Sanchez, J. Teisseire , E. Barthel, N. Chemin, J Am Chem Soc, submitted.4) A. A. Letailleur, Th. Richardot, C. Boissière, C. Sanchez, C. Couteau, G. Lérondel, E. Barthel, E. Søndergård, N. Chemin, and François Ribot, Advanced materials, submitted.
FF2: Assembly by Adhesive Transfer and Other Mechanical Techniques
Session Chairs
John Rogers
Kenneth Shull
Monday PM, November 28, 2011
Room 202 (Hynes)
2:30 PM - **FF2.1
Mechanics of Nanotransfer Printing for Applications in Electronics and Metamaterials.
John Rogers 1
1 , University of Illinois, Urbana, Illinois, United States
Show AbstractSoft, viscoelastic stamps provide useful vehicles for selective transfer of nanostructures from one substrate to another, in a way that can be exploited both for heterogeneous integration and nanofabrication. We describe the mechanics of advanced forms of transfer printing, and then outline the use of these methods in the construction of flexible/stretchable electronic devices, and large-area three dimensional metamaterials.
3:00 PM - FF2.2
Shear-Enhanced Adhesiveless Transfer Printing Techniques for Nanoscale Materials Assembly.
Andrew Carlson 1 , Hyun-Joon Kim-Lee 2 , Jian Wu 3 , Paulius Elvikis 4 , Placid Ferreira 4 , Yonggang Huang 3 , Kevin Turner 2 , John Rogers 1 4
1 Materials Science and Engineering, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States, 2 Mechanical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States, 3 Civil and Environmental Engineering, Northwestern University, Evanston, Illinois, United States, 4 Mechanical Science and Engineering, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States
Show AbstractMeeting the performance demands of many emerging microelectronic and optoelectronic technologies often require devices fabricated by large-scale integration of disparate classes of nanomaterials into spatially organized, functional arrangements. Transfer printing, a recently developed process which utilizes an elastomeric stamp to mediate transfer of prepatterned micro/nano-objects (i.e., ‘inks’, semiconducting nanomaterials and others) between a donor and receiver substrate, provides a scalable route for direct integration of diverse nanostructures and materials into single, unified systems. Transfer printing efficiency, particularly separation of the nanomaterial ‘ink layer’ from the viscoelastic stamp element, can be enhanced by engineering the stamp/ink interface to support mechanical loads that alter its effective adhesive strength. We demonstrate how targeted shear loading of single-post polydimethylsiloxane (PDMS) stamps can be used to reduce normal direction forces necessary to separate the stamp from silicon membranes in a controlled, repeatable manner during printing. Experimental studies combined with Finite Element (FE) modeling reveal critical factors influencing the shear printing process including geometrical constraints on stamp design and local stress distributions at the stamp/ink interface. Additionally, analytical expressions for shear strain in the stamp are developed. Systematic adhesiveless transfer printing yield studies and examples of partially suspended, overhanging structures and multilevel configurations of silicon membranes provide key practical demonstrations of shear-assisted printing capabilities.
3:15 PM - FF2.3
Measuring Micromechanical Adhesive Inking and Printing of Carbon Nanotube and Silver Nanowire Transparent Thin Films Using a Nanoindenter.
Evelyn Doherty 1 , Graham Cross 1
1 Crann, Trinity College Dublin, Dublin Ireland
Show AbstractAn emerging technique in nanofabrication is the use of the micro-contact adhesion of an elastomeric stamp to transfer nano-objects between source and target substrates. This technique has many outstanding advantages including the precise inking and printing of nano or micro objects of varied complexity1 for electronics, optical and medical applications, without the use of additional chemicals or processes such as etching. We have conducted a local mechanical analysis of the inking and printing of thin films of transparent silver nanowire and carbon nanotube networks (nano-networks). A nanoindenter was used with a novel micrometer scale elastomeric polydimethylsiloxane (PDMS) transfer tool to record and correlate displacement, load and dynamic stiffness with video microscopy analysis of transfer processes. The viscoelastic contact dynamics of our thin film PDMS transfer tool is tuned by varying parameters such as PDMS surface energy, complex modulus, film thickness, peak load, and unloading rate to influence interfacial energy release rates and detailed contact stress distributions. The mechanical analysis is enhanced by the establishment of a relationship between small amplitude dynamic contact stiffness and true contact size. Control of these parameters facilitates realization of transfer functions including seeding, inking and printing over a wide process space. The mechanisms of rupture and peeling of the nano-network films are thus investigated in terms of interfacial fracture due to these tuned parameters. Our results indicate that the detailed stress distribution in the contact is responsible for controlled and symmetric peeling and tearing of the nano-networks. We investigate the role of cavitation and cohesive failure of the PDMS with the underlying substrate and its role in the inking effect. We report on the transfer as a function of both PDMS tool and nano-network characteristics such as thickness and porosity. Comparisons and analysis will be presented with existing literature2,3 for systems of a similar configuration which have examined the inking and printing of elastic, continuous thin films. References: 1.Onoe, Shimoyama et al Three-dimensional integration of heterogeneous silicon micro-structures by liftoff and stamping transfer J. Micromechanics & Microengineering (2007) 2.Feng, Rogers et al Competing fracture in kinetically controlled transfer printing, Langmuir 23 (2007)3.Shull et al Adhesive Transfer of Thin Viscoelastic Films Langmuir (2004)
3:30 PM - **FF2.4
Adhesion Issues in Pattern Transfer.
Kenneth Shull 1
1 Materials Science and Eng., Northwestern University, Evanston, Illinois, United States
Show AbstractContact transfer of a thin layer from one surface to another forms the basis of a variety of pattern transfer processes. In these processes material transfer is controlled by the relative adhesion of the layer to a supporting surface and to a second surface that is brought into contact with it. The relevant transfer criterion can be posed as a fracture mechanics problem, where a contact line moves at a velocity that is determined by the applied energy release rate. Polymeric materials generally have a viscoelastic character, in which case the full functional relationship between the energy release rate and the crack velocity must be specified in order to quantify the adhesive behavior. In this talk the factors affecting this relationship will be summarized, and fracture mechanics concepts will be used to illustrate the factors enabling a thin film supported on a flexible substrate to be cleanly transferred from one surface to another.
4:30 PM - FF2.5
Electroplate-and-Lift (E&L) Lithography on Reusable, Patterned Ultrananocrystalline Diamond (UNCD) Templates for Rapid Prototyping of Micro- and Nanowires.
Lori Lepak 1 , Anirudha Sumant 2 , Ralu Divan 2 , Daniel Rosenmann 2 , Orlando Auciello 2 3 , David Seley 1 , Daniel Dissing 1 , Suzanne Miller 2 , Julia Weber 1 , Jessica Nordstrom 1 , Dylan Jones 1 , Corina Grodek 1 , Timea Hohl 1 4 , Bradley Stroik 1 , Morgan O'Connell 1 , John Knauf 1 , Michael Zach 1
1 Department of Chemistry, University of Wisconsin -- Stevens Point, Stevens Point, Wisconsin, United States, 2 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 3 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 4 Department of Experimental Physics, University of Debrecen, Debrecen Hungary
Show AbstractElectroplate-and-Lift (E&L) lithography has been developed as fast, simple, scalable technique for the controlled, solution-based, electrochemical synthesis of patterned metallic and semiconducting nano- and microwires. The wires are electrodeposited onto a reusable, non-sacrificial, multi-layered, lithographically patterned ultrananocrystalline diamond (UNCD)TM template. The template is made from alternating layers of UNCD, which is insulating, and nitrogen-incorporated UNCD (N-UNCD), which has nearly metallic conductivity. UNCD is used to isolate the top and bottom surfaces of the N-UNCD layer from the electrochemical bath. The diamond layers are lithographically patterned and dry etched to expose only edges of the N-UNCD layer, which is 80 nm thick. The initial nucleation of the nanowire is thus confined to the patterned edges of the N-UNCD. While the thickness of the N-UNCD layer establishes the minimum wire thickness, the maximum wire diameter is determined solely by the deposition time, independent of feature sizes in the template. Following electrodeposition, the nanowires may be removed by mechanically lifting them away from the template with scotch tape or other polymers, thus regenerating the template surface for subsequent depositions. Wires of the same or a different diameter, composed of any desired electrochemically depositable material, may subsequently be plated. Unlike all other methods of patterning nanowires, E&L lithography allows patterned nanowires to be quickly mass-produced, without requiring any additional vacuum or clean room processing after the initial fabrication of the template. This permits the study of nanoscale phenomena with minimal equipment and entry-level personnel. As a consequence, E&L lithography greatly expands the breadth of micro- and nanomaterials research projects which may be feasible at primarily undergraduate institutions, small companies without access to state-of-the-art clean rooms, and even institutions well-equipped with extensive fabrication facilities.
4:45 PM - FF2.6
PRINT: A Roll-to-Roll Method for the Fabrication of Shape and Size Specific NanoParticles.
Kevin Herlihy 1 , Mary Napier 1 , Marc Kai 2 , Jillian Perry 1 , Joseph DeSimone 1 2 3
1 Lineberger Comprehensive Cancer Center, UNC Chapel Hill, Chapel Hill, North Carolina, United States, 2 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 3 Chemistry, University of North Carolina, Chapel Hill, North Carolina, United States
Show AbstractA variety of top-down particle fabrication methods currently exist. These methods are unique in that they sculpt bulk materials to make nanomaterials with sizes, shapes and other interesting properties. Using the Particle Replication In Non-wetting Templates (PRINT®) process, we use elastomeric molds to gently fabricate micro- and nanoparticles. Molds are secured to a robust yet flexible poly(ethylene terephthalate) backing which gives the ability to scale up particle fabrication using a continuous roll-to-roll process, something that is not easily translated to other top-down fabrication techniques. The ability to control particle size, shape and composition is demonstrated. Particles are fabricated using a variety of matrices from pure drug to biologics to biodegradable polymers. Janus particles fabricated via multilayer filling steps or surface modification steps will also be discussed.
5:00 PM - FF2.7
Monolithic Integration of Continuously-Tunable Metallic Bumps, Grooves, and Apertures for Plasmonics and Nanophotonics.
Nathan Lindquist 1 , Timothy Johnson 1 , David Norris 2 , Sang-Hyun Oh 1
1 Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, United States, 2 Optical Materials Engineering Laboratory, ETH Zürich, Zürich Switzerland
Show AbstractPrecise fabrication of metallic nanostructures is critical for the emerging field of plasmonics and nanophotonics. Indeed, advances in nanofabrication technologies have to a large degree driven the rapid development of surface plasmon optics. To build a functional device and to carefully study surface plasmon physics, the precise engineering of metallic nanostructures is necessary. However, the integration of arbitrary arrangements of smoothly patterned bumps, grooves, and apertures over large areas remains a significant challenge. These implementation difficulties are compounded because as-deposited metal films are typically rough—which can limit surface plasmon propagation, degrade the performance of the device, and lead to sample-to-sample variations. In this abstract, we present a fabrication technique that uses template stripping of patterned metals for the large-scale, monolithic integration of bumps above, grooves into, and apertures through an optically-thick, ultrasmooth metallic film. We first fabricate a high-quality, reusable silicon template with focused ion beam (FIB) milling and FIB-induced deposition. Then, via template stripping, we show high-throughput, repeatable fabrication of metallic nanostructures with features that vary smoothly from ~100 nm above the metal surface to ~100 nm into the metal surface with 1-2 nm geometric tuning precision. Nanometric apertures through the metallic film are also possible. Such continuously-tunable plasmonic structures display spatially-dependent surface plasmon excitation and sharp spectral resonances. Using these same templates, we also demonstrate a unique "in situ" template stripping process with a mechanical nano-manipulator in the FIB chamber, giving the capability to arbitrarily "copy," “cut,” and “paste” these patterned metallic nanostructures. These methods will allow the development of high-quality plasmonic devices with minimal sample-to-sample variation, ultrasmooth patterned metallic surfaces, and many degrees of design freedom.
5:15 PM - FF2.8
Highly Stretchable Organic Electronics: Real-Device Fabrication by Three-Dimensional Writing.
Ji Tae Kim 1 , Jaeyeon Pyo 1 , Jonghyun Rho 2 , Jong-Hyun Ahn 2 , Jung Ho Je 1 , G. Margaritondo 3
1 Materials science and engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon Korea (the Republic of), 3 Faculté des Sciences de Base, Ecole Polytechnique Fédérale, Lausanne Switzerland
Show AbstractThe development of stretchable electronic devices is one of the most interesting challenges in modern technology (1). A substantial amount of research was focused on the realization of stretchable electrical interconnections. Recently, two innovative approaches to realize stretchable interconnections were developed, based on rubber-like elastomer/carbon nanotube composites (2) and wavy thin metals (3). Both strategies reach stretchability over 100 %, but are limited to passive interconnections – whereas stretchable devices require active components. Here, we demonstrate a variety of active electronic devices with extreme (>270%) stretchability using the organic conjugated polymer poly (3, 4 – ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS).PEDOT:PSS was already used for electronics and optoelectronics devices such as transparent electrodes, electrochemical transistors and electrochromic systems. The patterning techniques included soft lithography and inkjet printing. However, these methods are limited to two-dimensional structures with tensile fracture strain < 5 % (4), insufficient for stretchable electronics. We overcame this obstacle by implementing a versatile our 3D technique (5, 6) based on accurately 3D guiding of a PEDOT:PSS meniscus by pulling a solution-filled micropipette. We thus obtained 3D microwires with controlled dimensions, site-specific positioning and tunable electrical transport properties. These structures included 3D microarches with excellent stretchability above 270 % and no compromise on the electrical characteristics. Such microarches were then successfully tested as components of different active microdevices such as electrochemical transistors and photo-switches operating under extreme stretching conditions. The impact of these successful tests goes well beyond these specific devices and opens the way to many different classes of stretchable microdevices based on organic materials.*Email:
[email protected];
[email protected] References(1) J. A. Rogers, T. Someya, Y. Huang, Science 327, 1603 (2010).(2) K. -Y. Chun et al., Nature Nanotech. 5, 853 (2010).(3) B. Y. Ahn et al., Science 323, 1590 (2009).(4) U. Lang, J. Dual, Key Eng. Mater. 345, 1189 (2007). (5) J. T. Kim et al., Adv. Mater. 23, 1968 (2011) [Inside front cover](6) J. T. Kim et al., Adv. Mater. (submitted)
5:30 PM - FF2.9
Fabrication of Metallic Nanocomponents by Forging of Ni3Al-Nanoparticles.
Andreas Landefeld 1 , Joachim Roesler 1
1 Technische Universität Braunschweig, Institute for Materials, Braunschweig, Lower Saxony, Germany
Show AbstractThe trend to manufacture size reduced components at the micro- and nanoscale is obvious and becomes more and more state of the art in designing actuators, sensors and chips. In recent years, nanoscale fabrication has developed considerably, but the fabrication of freestanding nanosize components is still a great challenge. The fabrication of metallic nanocomponents utilizing three basic steps is demonstrated here. First, metallic alloys are used as factories to produce a metallic raw stock of nano-objects/nanoparticles in large numbers. These objects are then isolated from the powder containing thousands of such objects inside a scanning electron microscope using manipulators, and placed on a micro-anvil or a die. Finally, the shape of the individual nano-object is changed by nanoforging using a microhammer to get specific geometries such as discs and more complex components such as gears and wheels in the near future. The almost cubic particles are essentially defect-free, therefore, provide very high strength (σ>2500 MPa) in combination with excellent formability (|φ|>1,6). There are two approaches for forming these small particles. Upset forging is used to forge small discs (height<100 nm) and to shape the nanoparticle in specific areas. Press forging into nano-dies is used to forge more complex structures. In this way free-standing, high-strength, metallic nano-objects may be shaped into components with dimensions in the 100 nm range. By assembling such nanocomponents, high-performance microsystems can be fabricated, which are truly in the micrometre scale (the size ratio of a system to its component is typically 10:1).
5:45 PM - FF2.10
Comparative Assessment of High Performance Nanostructured Wicks for Phase-Change Heatspreaders.
Shakti Chauhan 1 , Matthew Misner 1 , Tao Deng 1
1 , GE Global Research, Niskayuna, New York, United States
Show AbstractAdvanced thermal management solutions are required to keep up with the dramatic increase in power density in electronic/optoelectronic systems. Heatpipe-based thermal heatspreaders are devices that address this issue by utilizing two-phase heat transfer to achieve considerably greater effective thermal conductivities than conventional solid conduction heatspreaders (e.g. Copper). The porus wick structure in such devices typically drives not only the fluid transport but also the effectiveness of evaporation/condensation phenomena. In this paper, various wick fabrication methods are developed and compared via experimental testing. The methods are compared based on thermal characteristics of the wick and wick-substrate interface, effective pore size and porosity measurements, chemical stability in aqueous environments and the thermal performance of fully packaged heatpipes. In addition, trade-offs related to manufacturability, including uniformity of wick properties and scalability are assessed.
Symposium Organizers
Graham Cross Trinity College
Andre Schirmeisen University of Muenster
Armin Knoll IBM Research-Zurich
Marco Rolandi University of Washington
FF3: Scanning Probe Fabrication I
Session Chairs
Tuesday AM, November 29, 2011
Room 202 (Hynes)
9:30 AM - **FF3.1
Using Heatable AFM Probes for the Nanolithography of Graphene, Polymers, and Nanoparticles.
Paul Sheehan 1
1 U.S. Naval Research Laboratory, U.S. Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractHeatable AFM probes have proven to be a powerful means of shaping advanced materials on the nanometer scale. We have used these probes in two ways—as a stylus for directly writing material [1,2] or as a heater to react small regions of existing films [3]. When used for deposition, the heat from the probe regulates the viscosity of an ink coated on its surface, a technique we call thermal Dip Pen Nanolithography (tDPN). Control over writing is exceptional—deposition may be turned on or off and the deposition rate easily changed without breaking surface contact. Moreover, the technique may be performed in UHV and is compatible with standard CMOS processing. tDPN has been successful at depositing metal, polymers, semiconducting and magnetic nanoparticles, quantum dots, etc. at speeds up to 200 µm/s. Importantly, the ability to shear and anneal the deposited material can engender new properties not present in the bulk such as conduction anisotropy in conducting polymers or to force alignment of nanoparticles into rows narrower than 10 nm.The heatable probes can also focus heat to localize chemical reactions. Of recent interest has been using this heat to convert chemically-modified graphenes back to pristine graphene. For example, the heatable probe can directly write graphene nanoribbons by locally reducing graphene oxide back to graphene. The reduced GO nanostructures show an increase in conductivity up to four orders of magnitude as compared to pristine GO. No sign of tip wear or sample tearing was observed. Variably conductive nanoribbons with dimensions down to ~12 nm have been produced in oxidized graphene films in a single step that is clean, rapid and reliable. The method is fast, applies both to conducting and insulating substrates, and is reproducible.[1] Nano Letters (2010) 1: 129[2] Soft Matter (2008) 4:1844–1847[3] Science (2010) 328:1373
10:00 AM - FF3.2
Nanoscale Tunable Reduction of Graphene Oxide.
Elisa Riedo 1 , Paul Sheehan 2 , Debin Wang 1 , William King 2 , Walt der Heer 1 , Claire Berger 1 , Seth Marder 1 , Suenne Kim 1
1 Physics, Georgia Tech, Atlanta, Georgia, United States, 2 , Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractGraphene’s high electronic mobility has been harnessed in devices such as transistors operating at gigahertz frequency; however, the zero band gap of graphene leads to high leakage currents in many applications. The reduced form of graphene oxide (GO) is an attractive alternative to graphene for producing large-scale flexible conductors and for creating devices that require an electronic gap. We present a tip-based thermochemical nanolithography (TCNL) method to control the extent of reduction of GO and pattern nanoscale regions of rGO within a GO sheet at speeds of several um/s. The relative increase in conductivity is as high as four orders of magnitude compared to pristine GO. GO was converted to rGO with a 100% yield in dozens of structures patterned on random locations in the GO film. No sign of tip wear or sample tearing was observed, indicating that the “carbon skeleton” is continuous across the GO/rGO junction. Variably conductive nanoribbons with dimensions down to 12 nanometers could be produced in oxidized epitaxial graphene films in a single step that is clean, rapid, and reliable.TCNL does not require any solvents or lithographic resists that could contaminate the sample. This is especially important because the electronic properties of graphene and graphene oxide vary strongly with surface doping. Fabrication of graphene-based transistors by TCNL will be demonstrated.References:Z. Wei, D. Wang, S. Kim, S.-Y., Kim, C. Berger, Y. Hu, A. R. Laracuente, S. R. Marder, W. P. King, W. A. de Heer, P. E. Sheehan, E. Riedo, Science, 328, 1373 (2010).R. Szoszkiewicz, T. Okada, S. C. Jones, T.-D. Li, W. P. King, S. R. Marder, and E. Riedo, Nano Lett. 7, 1064 (2007).D. Wang, T. Okada, R. Szoszkiewicz, S. C. Jones, M. Lucas, J. Lee, W. P. King, S. R. Marder and E. Riedo, Applied Physics Letters 91, 243104 (2007).D. Wang, V. K. Kodali, W. D. Underwood, J. Jarvholm, T. Okada, S. C. Jones, M. Rumi, Z. Dai, W. P. King, S. R. Marder, J. E. Curtis, E. Riedo, Advanced Functional Materials, 19, 3696 (2009).D. Wang, S. Kim, W. D. Underwood, W. P. King, C. L. Henderson, S. R. Marder, E. Riedo, Applied Physics Letters, 95, 233108 (2009)
10:15 AM - **FF3.3
Direct Write 3-Dimensional Nanopatterning Using Probes.
Urs Duerig 1 , Felix Holzner 1 , Philip Paul 1 , Michel Despont 1 , Armin Knoll 1
1 , IBM Reserach - Zurich, Rueschlikon Switzerland
Show AbstractA novel probe patterning method based on the local evaporation of organic resist materials been developed at the IBM Research Laboratory in Zurich [1-3]. A three dimensional relief pattern is written directly into the resist without the need for a development step. The technology has a number of unique attributes: High resolution patterning capability compatible with the requirements of future transistor technology; high patterning speed comparable to high resolution electron beam lithography, and direct writing of three dimensional relief structures with nm precision, which is not possible with any other technology. The resist material is decomposed and evaporated locally pixel by pixel using a hot tip. This can be done with high speed (500000 pixels per second, 20 mm/s scan speed), high accuracy (<10 nm) and excellent control of the patterning depth. Our scanning-probe-based patterning method also allows high-resolution imaging and hence accurate in-situ detection of features on the target substrate prior to the patterning process. For example, the natural roughness of the resist surface provides a unique marker for high-resolution stitching enabling the seamless writing of arbitrarily large fields. An other important aspect for lithographic applications is the ability to transfer the written patterns into Si using standard technology. We showed that 40x overall depth amplification can be achieved using an intermediate hard mask transfer step. The control of the third dimension in patterning is a novel feature which has been rarely explored in nano-technology. By combining our patterning technology with reactive ion etching, we demonstrated multilevel bit data recording at 99Gbit/in2 density in a poly-Si/SiO2 carrier for ultra-long retention archival data preservation. The relief structures written in the resist can also be used as template for the guided assembly of nano-particles. The interesting feature is that the temperature sensitive resist can be easily removed after the assembly step, and as a result, the particles are directly transferred to the target substrate preserving their position and orientation as demonstrated in an assembly experiment using 75 nm long and 25 nm diameter Au nano-rods. Combining in-situ imaging with the removable template strategy allows the precise registry of the assembled particles with functional elements on the target substrate, which is a unique asset for future applications. [1] David Pires, James L. Hedrick, Anuja De Silva, Jane Frommer, Bernd Gotsmann, Heiko Wolf, Michel Despont, Urs Duerig, and Armin W. Knoll, Science 328, 732-735 (7 May 2010)[2] Armin W. Knoll, David Pires, Olivier Coulembier, Philippe Dubois, James L. Hedrick, Jane Frommer, Urs Duerig, Adv. Materials 22, 3361-3365 (2010)[3] Philip C. Paul, ArminW. Knoll, Felix Holzner, Michel Despont andUrs Duerig, Nanotechnology 22, 275306 (2011).
10:45 AM - FF3.4
Thermochemical Nanolithography of Arbitrary-Shaped Ferroelectric Structures on Plastic, Glass and Silicon Substrates.
Suenne Kim 1 , Yaser Bastani 1 , Haidong Lu 2 , William King 3 , Seth Marder 1 , Kenneth Sandhage 1 , Alexei Gruverman 2 , Elisa Riedo 1 , Nazanin Bassiri-Gharb 1
1 , Georgia Institute of Technilogy, Atlanta, Georgia, United States, 2 , University of Nebraska-Lincoln, Lincoln, Nebraska, United States, 3 , University of Illinois Urbana-Champaign, Urbana, Illinois, United States
Show AbstractFerroelectric oxides are versatile smart materials that are attractive for a variety of nanometer scale applications owing to their switchable spontaneous polarization, pyroelectricity, and piezoelectricity (with high piezoelectric coefficients). However, the high processing temperatures required for their synthesis are mostly incompatible with other on-chip components, and the properties of these materials are often found to depend on the nanofabrication procedures. We report the creation of Pb(Zr_0.52Ti_0.48)O_3 (PZT) and PbTiO_3 (PTO) ferroelectric nanostructures in various shapes on platinized and plain plastic (Kapton) to silicon and soda-lime glass substrates, by mask-less thermochemical nanolithography (TCNL). An atomic force microscope (AFM) thermal tip is used as a local heat source to induce nanoscale crystallization of sol-gel precursor films. Ferroelectric lines with widths as narrow as 30 nm, spheres with diameters as small as 10 nm, and densities as high as 213 Gb/in^2 have been produced.
11:30 AM - FF3.5
Nanoscale Dislocation Patterning of Cubic Semiconductors by Atomic Force Microscopy.
Rodrigo Prioli 1 , Paula Caldas 1 , Clara Almeida 2 , Jingyi Huang 3 , Fernando Ponce 3
1 Physics, PUC-Rio, Rio de Janeiro Brazil, 2 Materials Division, INMETRO, Rio de Janeiro, Rio de Janeiro, Brazil, 3 Physics, Arizona State University, Tempe, Arizona, United States
Show AbstractThe development of nanopositioning systems allows the precise placing of atomic force microscopy tips, and the controlled application of forces of few nano Newtons on areas with dimensions close to the atomic scale. The tip displacement can be measured with nanometer precision while the force between the tip and the sample is varied. The pressure applied by the instrument tip may cause the generation of dislocations at an atomic scale by the slip of specific crystal planes in nanometer-scale volumes. The dislocations introduced at low forces are usually highly localized bellow the deformed area, opening the possibility of nanoscale lithography where the nature of a crystalline substrate is modified by the precise introduction of dislocations at specific surface sites. Dislocation patterns have been produced by atomic force microscopy scratching of (100) InP crystals along specific crystallographic directions with forces ranging from 7 uN to 120 uN. The mechanical deformation process was studied by atomic force microscopy and transmission electron microscopy. For a given applied force, deeper plastic flow has been observed in the <110> case than in the <100> case. Under increasing applied forces, plastic flow was first observed at 15 uN for <110>, and at 30 uN for <100>. The crystal deformation during a scratch event has been observed to consist of three stages: (a) surface conformation to the shape of the AFM tip during the early stages of the process, and it is associated with slip at the nanoscale with the formation of an inverted triangular region with high dislocation density; followed by (b) a sudden displacement (pop-in) that signals the beginning of downward slip at the bulk scale; and (c) for sufficiently large forces, recovery of the bulk elastic strain by upward slip (pop-up). The <110> scratch direction is aligned along the {111} slip planes, and yields at lower applied forces than in the <100> case. Scratching along the <110> direction generates anisotropic butterfly-like structures with mostly screw dislocations indicating rotational motion in the vicinity of the advancing tip. For <100> directions, the dislocations do not propagate far from the surface, possibly due to interlocking between dislocations on different slip planes. The influence of melting introduced by frictional heat has also been observed.
11:45 AM - FF3.6
Theoretical Study of Atomic Manipulation on Metals.
Martin Ondracek 1 , Zdenka Chromcova 1 , Cesar Gonzalez 2 1 , Pavel Jelinek 1
1 Department of Thin Films and Nanostrucures, Institute of Physics, AS CR, Prague Czechia, 2 , Instituto Ciencia de Materiales de Madrid, Madrid Spain
Show AbstractThe recent progress of the non-contact atomic force microscopy (nc-AFM) technique has enabled controlled manipulation of single atoms on various types of surfaces [1]. A potential energy landscape of the tip-sample interaction can be constructed from force maps recorded during the manipulation process. Moreover, both vertical and lateral forces necessary to move an atom can be directly estimated [2]. Surprisingly, the experimental findings on metal surfaces [2] show that only the lateral force component plays the decisive role in moving a single surface atom. This observation contrasts with the observations made previously on a semiconductor surface [3].We have carried out extensive theoretical simulations to get more insight into the manipulation of a single atom on a closed-packed metal surface, in particular the Cu(111) surface. We combine the total energy DFT calculations with classical Molecular Dynamics using Force Field potentials. We have investigated the conditions required for moving a Cu adatom on the Cu(111) surface with the AFM probe in terms of the atomic structure on the AFM tip termination, the distance of the tip from the surface, and the force acting between the tip and the adatom. We will discuss the implications for the mechanism of lateral atomic manipulation that result from using either a static STM mode at constant height or an oscillating AFM mode. References:[1] O. Custance et al., Nature Nanotechnology 4 (2009) 803.[2] M. Ternes et al., Science 319 (2008) 1066.[3] Y. Sugimoto et al., Phys. Rev. Let. 98 (2007) 106104.
12:00 PM - **FF3.7
New Technologies through Atom-Scale Crafting: New Microscopes and a Route Beyond the Semiconductor Roadmap to Ultra-Low Power Silicon Electronics.
Robert Wolkow 1
1 Physics, University Alberta, Edmonton, Alberta, Canada
Show AbstractThree examples of atom-scale crafting will be given. One involves making the ultimate needle – a sharp tip that terminates in one Tungsten atom, is very robust due to a covalent crust of Tungsten Nitride, and can be rebuilt, in situ, exactly as before. This tip is an important scan probe for atom scale fabrication, it is an extraordinary electron source, and it is the best known ion source for a new generation of scanning ion microscopes. Such ion sources will in turn serve as a new atom scale writing tool that is possibly more desirable than e-beam in some applications. Yet another variant, operated with Neon, may compete with the familiar liquid Gallium source FIB (focussed ion beam) for nano-scale machining.A home-made multi-probe, scanned probe microscope will be briefly described also. I will focus on the kinds of characterizations made possible by this new tool. Several similar commercial instruments are now available making such measurements more widely accessible. For example, atom-scale potentiometry can now be done with extreme sensitivity. Also, proto-devices can be directly probed without need for a fully lithographically connected structure.Finally I will mention a path toward a new atomic electronics technology we hope to soon commercialize. This silicon based proto-technology addresses the most pressing short coming of today’s CMOS – that is uncontrollable power density. Our new approach, an extension of that created by Craig Lent more than a decade ago, employs quantum-dot cellular automata to achieve extremely low power consumption. Larger ensembles of silicon dangling bonds can be viewed as quantum dot collectives, or artificial molecules. This beautiful and adaptable construct has long been viewed as a kind of ideal that is unfortunately beyond practical realization because of various problems – fabrication and low temperature requirements being foremost among those. We intend to make a functioning, room temperature, atomic silicon-based quantum dot cellular automata device. Demonstrations in this presentation will be limited to the basic building block – the 4 dot cell – and the biasing of that cell. We will as well describe some finer details of our developing characterization of such entities.
12:30 PM - FF3.8
Controlling Pattern Formation in Ferroelectric Nanolithography to Enable Multi Component Functional Device Properties.
David Conklin 1 , Sanjini Nanayakkara 1 , Tae-Hong Park 2 , Michael Therien 3 , Dawn Bonnell 1
1 MSE, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 3 Chemistry, Duke University, Durham, North Carolina, United States
Show AbstractIn spite of novel lithographic processes that enable new approaches to fabricating materials, directed assembly of multi-component hybrid devices remains a challenge. Ferroelectric nanolithography has the potential to overcome these challenges. This process combines polarization stamping or probe patterning with directed assembly. It exploits polarization dependent surface interactions to pattern nanoparticles, but the factors that control the particle size and distribution were not sufficiently well understood to produce hybrid nanostructures. Here the effects of photon energy, photon flux, and polarization vector orientation on ferroelectric domain specific photoreactions are quantified, leading to an understanding of the nanoparticle deposition mechanism. This understanding enables the size and separation of nanoparticles to be controlled, such that molecules can be linked to patterned nanoparticle arrays in order to form functional hybrid nanostructures. An electro- optical device was assembled that demonstrated enhanced photo conductivity due to plasmon interactions. These results define a pathway for Ferroelectric Nanolithography to be used to pattern a wide range of multi-component structures with applications ranging from optoelectronics to energy harvesting
12:45 PM - FF3.9
Scanning Probe Nanostructure Direct-Write: From Serial to Parallel Patterning.
Stephanie Vasko 1 2 , Adnan Kapetanovic 1 , Michael Brasino 1 , Vamsi Talla 3 , Hideki Sato 1 , Marco Rolandi 1
1 Materials Science and Engineering, University of Washington, Seattle, Washington, United States, 2 Chemistry, University of Washington, Seattle, Washington, United States, 3 Electrical Engineering, University of Washington, Seattle, Washington, United States
Show AbstractLarge-scale throughput of nanoscale heterostructures is fundamental for future semiconductor devices. We have developed an approach to nanostructure direct-write that exploits the tip of an atomic force microscope (AFM) to control the size, shape, and composition of nanostructures. The biased probe of an AFM reacts diphenylsilane or diphenylgermane to direct-write carbon-free (SIMS, x-ray PEEM) Si and Ge nano and heterostructures. Proof-of-concept SiGe nanostructures have also been demonstrated. The underlying chemical reactions occurring in the direct write process and deposition mechanism will be discussed. The general nature of the high field chemical reaction is demonstrated through parallel patterning via a flexible stamp approach. Efforts on expanding parallel printing mass manufacture by adapting this process to 4” mask aligner technology will be discussed. This high field approach to deposition of organometallic precursors could offer a low-cost, high throughput alternative for optical, electronic, and photovoltaic applications.
FF4: Fluidic and Directed Self Assembly Techniques
Session Chairs
Tuesday PM, November 29, 2011
Room 202 (Hynes)
2:30 PM - FF4.1
Toward Wafer-Scale Patterning of Freestanding Intermetallic Nanowires.
Romaneh Jalilian 1 , Sreenath Arva 2 , Davood Askari 3 1 , Jeremy Rathfon 2 , Jose Rivera 1 , Robert Cohn 2 , Mehdi Yazdanpanah 1
1 , NaugaNeedles , Louisville, Kentucky, United States, 2 ElectroOptics Research Institute and Nanotechnology Center, University of Louisville, Louisville, Kentucky, United States, 3 Department of Engineering, University of Texas at Brownsville, Brownsville, Texas, United States
Show AbstractIndividual metal alloy nanowires of constant diameter and high aspect ratio have previously been self-assembled at selected locations on atomic force microscope (AFM) probes by the method reported in Yazdanpanah et al (2005 J. Appl. Phys. 98 073510). This process relies on the room temperature crystallization of an ordered phase of silver–gallium. A parallel version of this method has been implemented in which a substrate, either an array of micromachined tips (similar to tips on AFM probes) or a lithographically patterned planar substrate, is brought into contact with a continuous, nearly planar film of melted gallium. In several runs, freestanding wires are fabricated with diameters of 40–400 nm, lengths of 4–80 μm, growth rates of 80–170 nm s−1 and, most significantly, with yields of up to 97% in an array of 422 growth sites. These results demonstrate the feasibility of developing a batch manufacturing process for the decoration of wafers of AFM tips and other structures with selectively patterned freestanding nanowires.
2:45 PM - FF4.2
Determining Metallicity of Nanowires via Their Mechanical Motions in Electric Fields.
Xiaobin Xu 1 , Kwanoh Kim 1 , Donglei Fan 1
1 Mechanical Engineering, Univerisity of Texas at Austin, Austin, Texas, United States
Show AbstractRecently intensive interest has been focused on nanowires due to their unique electrical properties. When measuring the electrical properties, one has to make electric contacts to the nanowires, which requires ardous fabrication process. In this work, we report an uncontact and undestructive appraoch to determine metallicity of nanowires via their mechanical motions in suspension in electric fields. Metallic (e.g. Au) and non-metallic nanwires (e.g. SiO2) have been rotated at AC electric fields of a few hundred kHz to 1 MHz. The nanoiwres exhibit distinctive rotation directions, e.g. clockwise for metallic nanowires and counter clockwise for non-metallic nanowires. Study of the physics relates the rotation direction to the electrical properties of nanowires. This research can be readily used to distinguish metallic/non-metallic nanowires.
3:00 PM - **FF4.3
Mechanical Aspects of Particle Self-Assembly from Liquid Menisci.
Philip Born 1 , Tobias Kraus 1
1 Structure Formation Group, Leibniz Institute for New Materials (INM), Saarbrücken Germany
Show AbstractParticles in a size range between 1 μm and 50 nm can be assembled from their dispersion by moving its meniscus over a substrate. Depending on the geometry and the substrate, uniform dense layers or sparse patterns of particles are deposited.A meniscus that moves over a patterned substrate at a non-wetting contact angle can selectively deposit particles on patterned regions (“capillary assembly”) [1]. The yield depends on the local particle concentration. Assembly with reasonable efficiency thus requires an “accumulation zone” that is enriched with particles. It is out of this volume that particles are deposited on the patterned sites of the template.Assembly from a wetting liquid yields continuous particle films (“convective assembly”) [2]. Particles are transported into a thin liquid film by convection, where they assemble into a densely packed layer. The assembly process relies on forces exerted by the liquid flow. It is strongly affected by the shape of the meniscus that confines the particles. We show that the mechanical behavior of the meniscus governs the attainable quality of assembled films [3].We will discuss the effects of fluid motion, gas-liquid interfaces and particle interactions on the outcome of these assembly processes. The results guide the choice of assembly setup geometries, process variables and particle types for high-quality particle assembly at high yields.[1] Kraus, Malaquin, Schmid, Riess, Spencer, and Wolf, Nature Nanotechnology 2007, 2, 570-576[2] Malaquin, Kraus, Schmid, Delamarche, and Wolf, Langmuir 2007, 23, 11513-11521[3] Born, Blum, Munoz, and Kraus, Langmuir 2011 ASAP, DOI: 10.1021/la2006138
3:30 PM - FF4.4
Nanoparticle Stripes, Ribbons and Grids via Flexible-Blade Flow Coating.
Dong Yun Lee 1 , Jonathan Pham 1 , Jimmy Lawrence 1 , Hyun Suk Kim 1 , Cheol Hee Lee 1 , Yujie Liu 1 , Cassandra Parkos 2 , Todd Emrick 1 , Alfred Crosby 1
1 Polymer Science & Engineering, University of Massachusetts Amherst, Amherst, Massachusetts, United States, 2 Mechanical Engineering & Materials Science, UC Berkeley College of Engineering, Berkeley, California, United States
Show AbstractWe present the controlled formation of nanoparticle stripe patterns on underlying substrates by flexible-blade flow coating. This technique exploits the combination of convective flow of highly confined nanoparticle solutions and programmed translation of a substrate to fabricate nanoparticle-polymer line assemblies. We achieve nanostripe dimensions of width below 300 nm, thickness of a single nanoparticle (~ 6 nm), and continuous length exceeding 5 cm. This multi-lengthscale control is facilitated by the use of a flexible blade, which allows capillary forces to self-regulate the uniformity of convective flow processes. We exploit solvent mixture dynamics and nanoparticle chemistry to enhance intra-assembly particle packing, leading to novel assembly properties including conductivity and free-standing mechanical flexibility and strength. This facile technique and the novel materials that are fabricated open up a new paradigm for integration of nanoscale patterns over large areas for various applications.
3:45 PM - FF4.5
High-Rate Electro-Fluidic Directed Assembly of Nanoparticles and Nanotubes.
Asli Sirman 1 , Cihan Yilmaz 1 , Jun Huang 1 , Sivasubramanian Somu 1 , Ahmed Busnaina 1
1 Mechanical and Industrial Engineering, NSF Nanoscale Science and Engineering Center for High-rate Nanomanufacturing , Boston, Massachusetts, United States
Show AbstractDirected assembly of nanoelements has been used to fabricate devices for diverse applications. The challenge in using such techniques consists of developing highly scalable, high-rate (fast) assembly techniques for placing nanoelements precisely on either conductive or insulating surfaces. Fluidic assembly, which employs the interfacial capillary forces, is a method used for assembling nanoelements onto many substrates (regardless of conductivity). However, fluidic assembly is diffusion limited and therefore, is a very slow process. During the fluidic assembly, nanoelement migration toward the substrate is only driven by the concentration gradient between the assembly region and bulk solution. On the other hand, electric field induced assembly techniques (such as electrophoresis) are very fast, however, they need a conductive surface and the assembly has to occur on a conductive substrate. This is not desirable for many electronics applications. Here, we introduce a new, high-rate electro-fluidic assembly technique that enables directed assembly on any type of insulating surfaces. The significance of this technique is that the assembly process is 100 times faster than fluidic assembly (the only technique used today on insulating surfaces). For example, fluidic assembly on a 3-inch wafer takes 25 hours; however, the presented method takes only 15 minutes to obtain fully assembled structures. In the electro-fluidic assembly process, a conductive film is used beneath the insulating substrate or film and field is applied through that conducting layer. Under the influence of the applied field, nanoelements move towards the template increasing the nanoelement concentration near the patterned template. A PECVD deposited silicon oxide layer on the top of a gold conductive film acts as the insulating layer. To achieve site-specific assembly a patterned PMMA layer is applied on the top of the insulating layer. A dip coater is used to provide precise and constant pulling speed of the template from the solution. Since the presence of an insulating (dielectric) layer inherently reduces the strength of the applied electric field, we increased the applied potential to effectively pull the particles towards the patterned template without damaging the insulating layer. Polystyrene Latex nanoparticles (50nm) and gold nanoparticles (50nm) have been successfully assembled. We have shown that the assembly is a function of pulling speed, pH of the solution and it is highly dependent on the applied voltage. We are able to achieve full particle coverage with trenches having different orientations and structures that exhibits the robustness of the assembly method for any two dimensional configuration. The process is being applied to SWNTs assembly to increase the assembly speed by two orders of magnitude. The assembled SWNT structures size range from 100nm to 3μm.
4:30 PM - **FF4.6
Structuring Materials at the Nanoscale: Nanopatterning Using Self-Assembled Masks.
Gerhard Wilde 1 2 , Yong Lei 1 2
1 Institute of Materials Physics, University of Muenster, Muenster Germany, 2 CeNTech, Center of Nanotechnology, Muenster Germany
Show AbstractLarge-scale arrays of nanostructures on substrates, such as semiconductor or metal nanoparticle arrays, have attracted considerable interest due to their unique physical properties and many potential applications in areas such as electronics, optoelectronics, sensing, high-density storage, and ultra-thin display devices. In the last two decades, the search for a highly efficient and low-cost nano-patterning method in fabricating ordered surface nanostructures with tunable dimensions and properties, has involved interdisciplinary and cross-disciplinary research and development with emerging technologies such as lithographic methods, self-assembly processes, and scanning probe techniques. Here, we present a new surface nano-patterning approach in fabricating ordered nanostructures, in which ultra-thin anodic alumina membranes are used as fabrication masks. Using the method, large-scale arrays of highly ordered nanostructures in the range of square centimeters can be fabricated on any substrate. The resulting nanostructures are characterized by highly defined and controllable size, shape, composition, and spacing of the nanostructures. Tuning of the properties of the arrayed nanostructures can be obtained by controlled adjustment of the structural parameters of the arrayed nanostructures. Compared to conventional lithographic methods, the present nano-patterning approach offers attractive advantages, such as large pattern area, high throughput, low equipment costs, and high flexibility and control options for ordered nanostructures with tunable properties. This new non-lithographic nano-patterning approach will be shown to be a rather general method in fabricating a wide range of ordered surface nanostructures with tuneable and unique physical and chemical properties that could be used in the fabrication of nano-devices with high performance and controllability. Funding by the Volkswagen Foundation, DFG (TRR61) and ERC is gratefully acknowledged.
5:00 PM - FF4.7
Three-Dimensional Hybrid Organic/Inorganic Heterojunctions Based on Rolled-up Nanomembranes.
Carlos Bof Bufon 1 , Juan Diego Arias 1 , Dominic Thurmer 1 , Christoph Deneke 1 , Oliver Schmidt 1 2
1 Institute for Integrative Nanosciences, IFW-Dresden, Dresden Germany, 2 Material Systems for Nanoelectronics, TU-Chemnitz, Chemnitz Germany
Show AbstractThe investigation of the electronic properties of molecular systems as well as their potential use for future device applications is strongly correlated with the way they are connected to the external world [1]. Nowadays, self-assembly is widely accepted as a standard technique to generate complex structures on many length scales [2]. One of such self-assembly processes consists of strained metal layers which spontaneously “curl up into close rolls” once they detach from their host substrate [3,4]. In this work we present a method based on self-released strained nanomembranes (metallic and/or semiconducting) for electrically contact single molecular layers. During release of the nanomembrane, the strain relaxation gives rise to a self-rolling process in which the membrane bonds back to substrate top surface where the thin organic layer was previously deposited. By this means, we are able to fabricate not only the standards metal-molecule-metal and metal-molecule-semiconductor structure configuration but also the unique semiconductor-molecule-semiconductor heterojunctions. In this last case, the type of doping and its concentration can be independently and precisely set for each electrode in order to tune the device electronic properties. Such a novel hybrid devices was observed to display completely different electric characteristics which are not expected or possible to be demonstrated by using their elements separately. In addition, the strained nanomembrane based electrodes provide a soft and robust contact on top of the organic film. Consequently, no damage to the organic layer and short circuits via pinholes, which is commonly observed in the SAM, has been observed. Since the contacting process takes place at room temperature, the metallic diffusion into the organic layer is suppressed. Furthermore, applying the self-rolling phenomenon, we achieve an approach that is fully integrative on a chip, and several components can be fabricated in parallel using well-established semiconductor processing technologies.[1] H. Haick and D. Cahen, Accounts of Chemical Research 41, 359 (2008).[2] G. M. Whitesides, B. Grzybowski Science 295, 2418 (2002).[3] O. G. Schmidt, K. Eberl Nature 410, 168 (2001).[4] C.C. Bof Bufon, J.D.C González, D.J. Thurmer, D. Grimm, M. Bauer, O.G. Schmidt, Nano Letters 10, 2506 (2010).
5:15 PM - FF4.8
A Novel Manufacturing Approach for Nanoscale Device Fabrication Using Directed Assembly of Nanoparticles.
Cihan Yilmaz 1 , Jun Huang 1 , Taehoon Kim 1 , Georgia Goutzamanidis 1 , Sivasubramanian Somu 1 , Ahmed Busnaina 1
1 NSF Center for High Rate Nanomanufacturing, Northeastern University, Boston, Massachusetts, United States
Show AbstractFor the past three decades the manufacturing of 2 and 3-D structures (conductive or semiconducting) specifically in the electronics industry relied on vacuum based or chemical based top-down processes. This approach has been successful so far, although costly, in scaling down the process to fabricate nanoscale features. However, as the device technology advances, conventional top-down fabrication techniques are facing significant challenges to manufacture smaller size features. The need to make nanoscale structures is essential for many applications besides electronics such as photonics, biotechnology, medical and materials. In this paper, we introduce a low cost, non-vacuum based, room temperature manufacturing process for fabricating nanoscale features. In this process, colloidal nanoparticles are precisely assembled and simultaneously fused into 2 and 3-D nanostructures in a single step using externally applied electric field. Nanostructures made of metal, semiconductor or polymer can be fabricated without requiring any surface treatment or modification. Using this technique, we manufactured arrays of gold (Au) and copper (Cu) nanostructures down to 25nm features size with an aspect ratio of up to 6 over large areas. TEM (transmission electron microscopy) characterizations reveal that these nanostructures have polycrystalline nature. The resistivity of the assembled Au nanostructures is 1.96×10-7 Ω●m. This resistivity is comparable to values reported in literature for similar Au nanostructures fabricated using conventional methods. The control of nanostructure dimensions via assembly parameters such as the voltage, frequency, time and particle concentration is shown. The crystalline nature and electrical characteristics of nanostructures under different assembly conditions is examined. The results show that this approach can immediately address scalability problems in the CMOS interconnect technology. In addition, the manufactured 3-D nanostructure arrays can enable exploration of new nanoscale device architectures with improved device performance and functionality for the applications in surface-enhanced Raman spectroscopy, plasmonic based biosensing, 3-D solar cells and advanced batteries.
5:30 PM - FF4.9
Directed Assembly and Transfer of Single Wall Carbon Nanotubes Using Damascene Templates.
Hanchul Cho 1 , Sivasubramanian Somu 1 , Jun Huang 1 , Ahmed Busnaina 1
1 Center for High-rate Nanomanufacturing (CHN), Northeastern University, Boston, Massachusetts, United States
Show AbstractLarge scale directed assembly of nano elements followed by transfer would lay the foundation for realizing cost effective manufacturing methods for devices comprising of nanoscale elements with unique properties. For directed assembly, solution based electrophoresis technique has been widely used to fabricate nano-structures, because of its speed and scalability. It can also be carried out at room temperature and pressure. When electrophoresis is employed to assemble nanoelements on metallic nanowires non-uniform potential arises as result of high resistance introduced by the nanowires. Moreover in these structures the metallic electrodes lie on the top of the insulating substrate forming 3D topographical patterns, which during transfer peel off due to poor adhesion. Here, we have developed a damascene template, fabricated by micro/nanofabrication process and chemical mechanical polishing methods (CMP) to overcome the difficulties mentioned above. In this damascene template the metallic micro and nanowires are connected to a conductive film underneath the insulating substrate and CMP is used to ensure that they are flushed in with the insulating substrate. Hence not only a uniform potential develops across both the metallic nano and micro features resulting in uniform assembly density but the assembled nanoelements can also be easily transferred. Also the template can be reused thousands of time for the assembly and the transfer without any additional processes such as patterning, stripping and sacrificial layer remove/deposit enabling high-rate manufacturing process. For highly organized and high density SWNT assembly on the damascene template, electrophoresis and dip coating methods were used. Here gold was used for the metal electrodes while SiO2 is used as the insulating layer. Self assembled monolayer (SAM) was selectively assembled on SiO2 such that the surface energy of the SiO2 changed to being hydrophobic. The approach demonstrated highly organized and uniformly dense SWNTs assembly on both micro and nano features. SWNTs were then transferred onto PMMA film and PET films at temperatures higher than glass transition (TG) temperature of polymers through the transfer method.
5:45 PM - FF4.10
Charge Transfer-Driven Molecular Self-Assembly at Organic/Metal Interfaces.
Roberto Otero 1 2 , Christian Urban 1 , Jonathan Rodriguez-Fernandez 1 , Yang Wang 3 , Raul Garcia 4 , Marta Trelka 1 , Manuel Alcami 3 , Jose Maria Gallego 5 2 , Maria Angeles Herranz 4 , Fernando Martin 3 , Nazario Martin 4 , Rodolfo Miranda 1 2
1 Dep. de Fisica de la Materia Condensada, Universidad Autonoma de Madrid, Madrid Spain, 2 , IMDEA-Nano, Madrid Spain, 3 Dep de Quimica, Universidad Autonoma de Madrid, Madrid Spain, 4 Dep de Quimica Organica, Universidad Complutense de Madrid, Madrid Spain, 5 , Instituto de Ciencia de Materiales de Madrid - CSIC, Madrid Spain
Show AbstractOrganic heterostructures based on blends of molecules with electron-accepting (large electron-affinity) and electron-donating (small ionization potential) character display interesting electrical and optical properties with promising technological applications. For example, they show electroluminiscence for Organic Light Emission Diodes (OLEDs), photovoltaic response for solar cell devices and one-dimensional conduction for low molecular-weight metallic films, while strong acceptors or donors are the basis for metal-organic magnets. These blends of molecules are deposited onto or contacted with metallic layers and their performance depends crucially on the alignment of energy levels, the molecular nanostructure and crystalline perfection. Interfaces between organic species with either donor or acceptor character and metal surfaces are, thus, of paramount importance for the performance of the devices described above. This observation has motivated a large effort aimed at understanding the electronic structure of organic/metal interfaces and, in particular, the alignment of the energy levels at the interface related to the charge transfer between the organic donor or acceptor species and the metallic surface. Charge transfer, however, not only leads to modifications in the alignment of energy levels; usually, it is also related to structural transformations in both donating and accepting species. Unfortunately, too often it is assumed that the substrate is just an inert spectator, playing no active role in the supramolecular organization. We describe here experiments (STM, XPS) and theoretical simulations that unequivocally demonstrate that for strong charge transfer systems, such as the organic acceptor dicyanoquinodimine (DCNQI) deposited on Cu(100) both the molecules and the substrate suffer strong structural rearrangements that may even control the resulting molecular ordering. In particular we will show that electron transfer from the metal to the molecule catalyzes a cis-trans isomerization reaction that further determines the subsequent assembly of the isomers on the surface. The reaction is thermally activated, in such a way that the resulting self-assembled structure turns out to be temperature dependent. Neglecting the role of the metal electrode as a source or sink of electron charge might, thus, lead to major errors in our expectations about how organic molecules self-assemble on solid surfaces.T.-C. Tseng, C. Urban et al. Nature Chemistry 2, 374 (2010)
Symposium Organizers
Graham Cross Trinity College
Andre Schirmeisen University of Muenster
Armin Knoll IBM Research-Zurich
Marco Rolandi University of Washington
FF5: Scanning Probe Fabrication II
Session Chairs
Wednesday AM, November 30, 2011
Room 201 (Hynes)
9:30 AM - FF5.1
Nanopatterning on Soft Complex Surfaces.
Albena Ivanisevic 1
1 , NCSU, Raleigh, North Carolina, United States
Show AbstractScanning probe based lithography has been widely used to explore and manipulate micro- and nanoscale surfaces. Many efforts have been directed towards engineering microfabricated devices that can function as ink cartridges and well systems. We present a simple modification scheme that allows one to place ink-reservoirs on cantilevers for chemical patterning by utilizing living spores of Bacillus Subtilis. AFM tips terminated with spore cells are used to directly pattern onto glass and tissue surfaces. The spore cells act as sponges and eliminate the need to use macrofabricated ink reservoirs during lithography. By varying the size of the spore at the end of the cantilever we can increase and decrease the gap between the spore tips and the surface. Therefore we can produce controlled, actuated patterning on the tissues without the need to heat, or apply current to forcibly actuate the tips. This results in essentially a low force patterning technique. Further, the tunable nature of the tips makes this technique applicable to a wide variety of users far beyond any other such developed technique. Variations to the microparticle system, such as progressively smaller spores or particles, could allow for complex actuation schemes.
9:45 AM - **FF5.2
Advances in Atomic Force Microscopy-Based Nanolithography: Molecular Architectures and Nanoelectronic Sensors.
Ricardo Garcia 1
1 , CSIC, Tres Cantos, Madrid, Spain
Show AbstractIn this contribution two application of AFM-based nano-oxidation are presented. AFM nanolithography can be applied to to build molecular architectures and in the process to pattern functional materials with nanoscale accuracy. The selective deposition is driven by the electrostatic interactions existing between the molecular materials and nanoscale features. Specifically, by combining a top-down tip-based nanolithography and bottom-up electrostatic interactions it is possible to form regular arrays of protein molecules with an accuracy that matches the protein size (~10 nm). Silicon nanowires compatible with integrated circuit technologies have great potential for the development of fast and very sensitive chemical and biological sensors. Atomic force microscope oxidation nanolithography shows its capacity to fabricate single-crystalline silicon nanowires and to position them with great accuracy in a circuit lay-out. AFM oxidation nanolithography is applied to define a very narrow silicon oxide mask on top of a silicon-on-insulator substrate. In a plasma etching, the silicon oxide mask protects the silicon underneath from the etching process while the uncovered part of the Si layer is etched away. This generates a silicon nanowire with a rectangular section. The nanowire can be integrated into device to be the main element of a field effect transistor. The fabricated silicon nanowire transistors show good electrical characteristics. The nanowires can be used to detect different optical, chemical and biological interactions.
10:15 AM - FF5.3
A Bio-Inspired Approach to Tip-Based Nanofabrication.
Sungwook Chung 1 3 , Debin Wang 2 3 , Jonathan Felts 4 , Iva Urbanova 3 , Martina Morrissey 3 , Frank Svec 3 , Woojae Chung 1 5 , Seung-Wuk Lee 1 5 , William King 4 , Jim DeYoreo 2 3
1 Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 4 Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States, 5 Department of Biomolecular Engineering, University of California Berkeley, Berkeley, California, United States
Show AbstractDeveloping generic platforms to organize discrete molecular elements and nanostructures into deterministic patterns at surfaces is one of the central challenges of nanotechnology. To address this challenge, we are developing a tip-based approach to fabrication of nanowires that relies on patterning of peptides selected for their ability to induce material-specific formation of inorganic solids under mild reaction conditions. Nanowire dimensions are controlled by generating a steep temperature gradient away from the tip via thermal dip-pen nanolithography (tDPN). The peptides are linked to the substrate either through a base self-assembled monolayer (SAM) patterned via contact printing or photografted, thiol functionalized polyethylene (PE) polymer patterned via tDPN. For the case of SAMs, the region surrounding the active patterns is passivated with a hydrophobic SAM such as octadecane thiol. When using the polymers, which provide a means for patterning on insulating substrates, peptide linkages are established through UV activated grafting of glycidyl methacrylate followed by reaction with cysteamine to produce exposed sulfhydryl groups. Pattern dimensions can be rapidly varied by changing the temperature of the probe and that the temperature dependence of the pattern dimensions exhibits an Arrhenius dependence, giving an activation barrier of 167 kJ/mol that reflects detachment from the tip and adsorption to the surface. When peptides selected for their ability to nucleate Au nanoparticles from an auric acid solution are linked to either the SAMs or thiol functionalized PE polymer, Au nanoparticle films grow on the patterns. The areal density, vertical film thickness and average particle size depend strongly on solution conditions. Introduction of silver ions to the solution enhances nucleation density, producing nearly continuous gold films. Results of AFM studies on the formation of the Au nanoparticles as well as the formation of ZnS nanoparticles on both selected peptides and whole phage virus will be discussed.
10:30 AM - **FF5.4
Nanostructured Lipid Multilayer Fabrication by Dip-Pen Nanolithography and Microcontact Printing.
Steven Lenhert 1
1 , Florida State University, Tallahassee, Florida, United States
Show AbstractLipids have several material properties that make them suitable as inks for nanofabrication and related applications. For instance, the fluidity or viscosity of phospholipids can be tuned by the hydration, or humidity [Small 2007 & 2008]. This allows control of ink transfer from an atomic force microscope tip (in the case of dip-pen nanolithography), or coating of elastomeric stamps in the case of microcontact printing. Being amphiphilic, lipids adhere to a variety of surfaces, making it possible to use them to noncovalently functionalize surfaces. As lipids are also lyotropic crystals, they tend to self organize in water to form lipid bilayers (e.g. which form the basis of cell membranes), a variety of nanostructured morphologies can be formed under the right conditions. Finally, the innate biocompatibility of phospholipids, insolubility in water [Scanning, 2010], and ability to encapsulate functional materials within multilayered nanostructures makes them suitable for a variety of biological applications. This talk will outline the underlying mechanics behind dip-pen nanolithography and microcontact printing of lipid micro- and nano-structures on surfaces in the context of applications for biosensor fabrication [Nature Nanotechnology, 2010], drug and gene delivery, and model cellular systems.
11:30 AM - FF5.5
On-Demand Written Nanoscale Organic Electronics.
Joseph Shaw 1 2 , Thomas Anthopoulos 1 2
1 Centre for Plastic Electronics, Department of Physics, Imperial College, London United Kingdom, 2 , EPSRC, Swindon United Kingdom
Show AbstractOrganic semiconductors are cheap and easy to implement in electronic devices such as transistors, as compared to traditional silicon-based electronics. However, because the majority of organic semiconductors have low charge carrier mobilities and lack sub-micron scale patterning methods, their use to date has been limited to large area, low-end electronic applications. One way of circumventing these problems is through the development of novel fabrication paradigms and the realization of nanoscale devices with improved performance characteristics. Here, we report on the use of a novel patterning methodology called thermochemical nanolithography (TCNL). This method is based on the use of a heated atomic force microscope (AFM) tip, which is scanned over a target material to induce carefully controlled chemical reactions at the nanometer scale. By combining the TCNL technique with a thermally activated organic precursor we are able to define nanoscale organic transistors and integrated circuits based on on-demand written semiconducting nanoribbons on virtually any type of substrate including glass and plastic. As the organic precursor we utilized a low conversion temperature pentacene precursor dissolved in an organic solvent. The solution was spin cast onto the substrates containing prepatterned electrodes. The heated AFM tip was then scanned over the film to define pentacene nanoribbon semiconducting channels between electrodes, with desired shape and size with ultra high spatial resolution (feature sizes from sub-50 nm up to 90 μm). Nanoribbon transistors were found to exhibit hole mobilities on the order of 10^-3 cm2/Vs, a value similar to that obtained from thin-film transistors based on the same pentacene precursor. By combining two such nanoribbon transistors, we were also able to demonstrate the first ever TCNL defined integrated circuit. The present work is an important step towards organic nano-size electronics and defines a milestone for the use of TCNL for the rapid prototyping of truly nano-scale opto-electronics.
11:45 AM - **FF5.6
Luminescent Organic Semiconductors Nanostructures via Scanning Probes Patterning.
Franco Cacialli 1
1 , University College London, London United Kingdom
Show AbstractWe interpret nanotechnology as the ability to produce nanostructures at will, rapidly and reproducibly over large areas, for a variety of different materials, since this is necessary for exploitation of the full potential of nanoscience, i.e. of the physical and chemical processes taking place at the nanoscale. Within this context we are particularly interested in direct writing of organic semiconductors nanostructures, since they provide a remarkably versatile “materials platform”, with functional properties suitable for electronics and optoelectronics, sensors, and, possibly, biomedical applications. In addition to our latest results on scanning near-field optical lithography (SNOL) of photosensitive conjugated polymers (or of their precursors), that enabled us to achieve minimum features of 60 nm, we present an approach to high-resolution lateral patterning of electroluminescent and/or inert polymer systems, based on scanning thermal lithography (SThL) of thin films prepared on a variety of substrates. Minimum feature sizes of less than 30 nm are possible, despite the use of micron-sized thermal probes, as well as fast writing speeds of up to 100 micrometer/s. We investigate the origin of this high resolution by both experiment and finite element modelling of the tip-sample system, and find that these resolutions can be achieved with a tip-sample contact area of 100 nm. We predict a further resolution enhancement upon adoption of an optimised probe, and show that similar resolution can be obtained on both thermally insulating or conducting substrates.
12:15 PM - FF5.7
Crystallization of 2D Liquid Layers on Rubrene Crystals by Mechanical Stimulation with Atomic Force Microscopy.
Koichi Sudoh 1 , Daisuke Takajo 2 , Takafumi Uemura 1 , Kazumoto Miwa 1 , Jun Takeya 1
1 The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan, 2 Research Center for Structural Thermodynamics, Osaka University, Toyonaka, Osaka, Japan
Show Abstract Organic semiconductors offer the unique characteristics to develop flexible and printable electronics. For fabrication of organic semiconductor devices, molecular level control of the surfaces of organic crystals and thin films is required. Rubrene is known as a high mobility organic semiconductor material. Recently we have discovered that the surface of rubrene crystals is covered by 2D liquid layer. In this paper, we demonstrate that tapping mode atomic force microscopy (AFM) can be used to crystallize molecules in the 2D liquid layer on rubrene crystals. This AFM-induced crystallization has potential to produce 2D nanoscale patterns of semiconducting molecular crystalline domain in the insulating liquid layer. For the experiment we used high quality single crystals of rubrene grown by physical vapor transport method. AFM observations were performed on the (001) surface of a plate-shaped rubrene crystal placed on a Si substrate in tapping mode with a silicon cantilever in air atmosphere. The (001) surfaces of as-grown rubrene crystals are extremely flat; they are composed of molecularly flat terraces and rather low densities of mono-molecular steps. However, the surface of the as-grown crystals is frequently covered by a 2D liquid layer, in which the orientation and arrangement of molecules are disordered. We find that the surfaces covered by 2D liquid layer are unstable against tapping mode AFM scanning. During successive AFM scanning, many 2D islands nucleate and grow in the liquid layer. In contrast, the surface of the 2D islands is stable against AFM scanning. The anisotropic shapes of the 2D islands are consistent with the underlying lattice of the rubrene crystal, suggesting that crystallization of the 2D liquid occurs due to mechanical stimulation during AFM scanning. The rate of this probe-induced crystallization depends on various factors such as the parameters for AFM scanning and the spring-constant of the AFM cantilever. We demonstrate that extremely broad molecularly ordered regions wider than 10 μm × 10 μm in area can be formed by successive AFM scanning.
12:30 PM - FF5.8
Sub-Wavelength Patterning of Azobenzene-Polymers for Photonic Applications.
Antonio Ambrosio 1 , Pasqualino Maddalena 1 , Andrea Camposeo 2
1 , CNR-SPIN Napoli and Dipartimento di Scienze Fisiche, Università degli Studi Federico II, Napoli Italy, 2 , NNL, Istituto Nanoscienze-CNR, Università del Salento, Lecce Italy
Show AbstractAzobenzene-containing polymers have been largely studied as promising materials for optical data storage. Complete trans-cis-trans isomerization cycles of the azo-groups may be driven by suitable laser light. Consecutive isomerization cycles of the azo-groups lead to a statistical net orientation of the azobenzene molecules with subsequent photo-induced birefringence and mass migration on the free surface of the polymer. The reasons for the surface modification following azo-groups isomerization are still matter of discussions [1]. Among all proposed models, a promising approach is based on classical laminar flow (Navier-Stokes equations) and has already described some experimental observations [2,3].We have used the unique characteristics of near-field optical microscopy (SNOM) [4] to write and read photo-induced features and to investigate in situ the dynamics of the mass migration from its very early stage. Single protrusions (dots 100-200 nm wide) are written by exposing the polymer to the near-field of a commercially available SNOM fiber and the dot growth is described in terms of Navier-Stokes equations. Dot growing followed for various sample temperatures, both below and above the glass transition temperature of the materials, shows the expected decrease of the dot height versus the temperature increase.Furthermore a large scale patterning process has been developed based on a feedback assisted reflection approach. This technique allows large area patterning (few millimeters) keeping the dimensions of the topographical features down to sub-wavelength scale.[1] A. Ambrosio, M. Allegrini, G. Latini, F. Cacialli, Appl. Phys. Lett. 87, 033109 (2005) [2] C. J. Barrett, P. L. Rochon, A. L. Natansohn, J. Chem. Phys. 109, 1505 (1998)[3] K. Sumaru, T. Fukuda, H. Matsuda, T. Yamanaka, J. Appl. Phys. 91, 3421 (2002)[4] A. Ambrosio, A. Camposeo, P. Maddalena, S. Patanè, M. Allegrini, J. Microsc. 229, 307 (2008)
12:45 PM - FF5.9
Nanoprinting of Gold on Flat and Rough Surfaces Using Voltage Controlled Fountain Pen Nanolithography.
Tali Yeshua 1 , Aaron Lewis 1 , Yossi Bar-David 2
1 Computer Science & Engineering , Hebrew University of Jerusalem, Jerusalem Israel, 2 , Nanonics Imaging Ltd., Jerusalem Israel
Show AbstractA method of atomic force controlled electrically driven nanoprinting has been developed. The technique allows for control of better than 50 nm in line widths and close to a nanometer in height of the written structures. The technique appears to be quite versatile and allows for the writing on even rough surfaces with full control of the nanowriting process by the electrical manipulation of ink ejection. Two different inks are used one is based on gold colloids with a diameter of 1.4 nm while the other is based on ionic solutions of gold.
FF6/SS10: Joint Session: Fundamentals of Mechanical Nanofabrication
Session Chairs
Matthew Begley
Mark Robbins
Wednesday PM, November 30, 2011
Constitution A (Sheraton)
2:30 PM - **FF6.1/SS10.1
Scaling Relationships for Synthetic Nacre and Their Implications for Materials Development.
Matthew Begley 1
1 , University of California, Santa Barbara, Santa Barbara, California, United States
Show AbstractSynthetic brick and mortar microstructures that mimic nacre (abalone shell) create new opportunities for high performance materials, provided the constituent properties can be controlled down to small scales. This talk will outline scaling laws that relate brick strength, mortar ductility and geometric length-scales to macroscopic modulus, strength and toughness. These scaling laws enable the generation of mechanism maps that illustrate regimes of brick failure and interface rupture, as a function of constituent properties. Inherent trade-offs between modulus, strength and toughness will be outlined and related to transitions in failure mechanisms. An important feature of the results is that the ideal brick size that optimizes strength and toughness depends strongly on the ductile properties of the mortar (and vice versa), and the interface strength that is controlled by bonding at the nanoscale. Using these models, processing targets for synthetic materials will be detailed in terms of geometry and constituent properties. The talk will conclude with a brief discussion of material synthesis via ink-jet printing of three-dimensional structures, with a focus on the key processing challenges that must be addressed to realize the material properties identified with the above models.
3:00 PM - FF6.2/SS10.2
Collective Mechanical Behavior of Multilayered Colloidal Hollow Nanoparticle Arrays.
Jie Yin 1 3 , Markus Retsch 2 3 , Edwin Thomas 2 3 , Mary Boyce 1 3
1 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Institute for Solider Nanotechnologies, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractHollow colloidal nanoparticle arrays have become a focal point of studies for applications in drug delivery and nanostructured materials, where the mechanical behavior of these arrays is of great importance in fulfilling the diverse application functions. Here we explore the collective mechanical behavior of two-dimensional (2D) monolayer and three-dimensional (3D) multilayer assemblies composed of close-packed arrays of hollow silica nanoparticles (NP) using a spherical nanoindentor. Such ordered multilayer arrays are self-assembled through the vertical deposition method. Several types of well-defined hollow NPs and their assembled monolayer, bilayer and trilayer arrays are studied with constituent NPs radii ranging from 100 to 300nm and shell thickness ranging from 14 to 44nm. The consecutive contacting of the indentor with an increasing number of NPs results in a nonlinear increase of the indentation force with penetration depth. Experimental results showed that the indentation load became increasingly lower as the number of layers was increased when compared at the same penetration depth, which leads to the compliant response of multilayer films. Micromechanical analytical models alongside with finite element method (FEM) simulations are employed to reveal the underlying deformation mechanisms during the indentation on 2D and 3D NP arrays. For 2D monolayer films, each contacted hollow NP successively locally bends, flattens, and then locally buckles. Based on the point-load solution of an elastic shell, the indentation load-displacement curves are predicted and the Young’s modulus of an individual particle is extracted from the measured load-displacement behavior of a monolayer array. For 3D multilayer films, a simplified parallel spring model is established to model the compliant mechanical response of multilayered NP arrays. In the trilayer NP arrays, the hexagonal close packing (HCP) and face centered cubic (FCC) packing lead to the identical indentation force-displacement curves, which implies the neglected effect of different packing methods. This study may provide useful insights and guidance for constructing high performance lightweight NP films and coatings with potential applications in tailoring stiffness and mechanical energy absorption.
3:15 PM - FF6.3/SS10.3
Tailoring and Probing Particle-Polymer Interactions in PMMA/Silica Nanocomposites.
Meng Qu 1 , Gregory Blackman 2 , Jeffery Meth 2 , Gordon Cohen 2 , Kenneth Sharp 2 , Krystyn Van Vliet 1
1 , MIT, Cambridge, Massachusetts, United States, 2 Central Research & Development, DuPont Nanocomposite Technologies, Wilmington, Delaware, United States
Show AbstractThe unique physical and mechanical properties of polymer nanocomposites have been attributed to the interfacial interactions between the organic matrix and nanoscale particles. We demonstrate the potential to tune this interaction between poly(methyl methacrylate) (PMMA) and silica nanoparticles, as a function of either nanosilica surface chemistry or polymer reactivity. Functionalized nanosilica was mechanically deposited on the surface of PMMA films, and the system then heated above the polymer glass transition temperature. Rates and extents of nanoparticle sink-in were quantified by timelapse AFM imaging, showing that the strength of particle-matrix interactions was predicted directly by polymer-particle interaction energies. Nanocomposite films created via this approach exhibited significantly enhanced elastic moduli and scratch resistance. This direct quantification of mechanical optimization via nanoparticle-polymer interfacial chemistry enables new approaches to rapidly tune nanocomposite performance.
3:30 PM - FF6.4/SS10.4
Mechanical Nanofabrication and the Origin of Life.
Helen Hansma 1
1 Department of Physics, University of California, Santa Barbara, California, United States
Show AbstractNanoscale work may have been a major energy source for the origin of life. According to the Mica Hypothesis [1], life originated between the sheets of muscovite mica, whose aperiodic up and down movements provided an endless source of mechanical energy for making and breaking covalent bonds, rearranging polymers, and blebbing off lipid micelles and protocells in the earliest form of cell division. This hypothesis for the origins of life is consistent with the behavior of biological macromolecules, which often have reproducible internal motions. The internal motions of many macromolecules are simple up-and-down motions such as the motions that occur between mica sheets in response to temperature change or water flow. The Mica Hypothesis for the origins of life evolved from research on biological Atomic Force Microscopy (AFM) [2]. 1.Hansma, H. G., Possible origin of life between mica sheets. Journal of Theoretical Biology 2010, 266, 175-188.2. The research on biological AFM was supported by NSF BIO MCB and NSF BIO DBI.
4:15 PM - **FF6.5/SS10.5
Nanomechanical Properties of Amorphous Polymers.
Ting Ge 1 , Mark Robbins 1
1 Physics and Astronomy, Johns Hopkins Univ., Baltimore, Maryland, United States
Show AbstractNanomechanical properties of amorphous polymersThis talk will describe simulation studies of the molecular mechanisms underlying the mechanical response of glassy polymers with an emphasis on regimes that may be relevant to nanopatterning and nanoassembly. First yield and strain hardening will be discussed. Strain hardening is associated with increased rates of plastic deformation as polymers become oriented by strain. Strain from previous deformation results in anisotropic mechanical properties, but the flow stress can be collapsed on a single master curve as a function of molecular orientation [1]. Anisotropy from strain hardening may impose limits on fabrication or offer opportunities for tailoring mechanical response. The next topic will be strengthening of polymer interfaces through thermally or mechanically driven interdiffusion. This is a common means of welding components or healing cracks at macroscopic scales. Simulations show a clear connection between the evolution of mechanical strength and the formation of entanglements across the interface. The final section of the talk will discuss interfacial fracture and sliding at polymer/crystal interfaces. The role of adhesive energies and surface roughness in determining the mode of failure and peak stress will be described.[1]. T. Ge and M. O. Robbins, “Anisotropic plasticity and chain orientation in polymer glasses,” J. Polymer Sci. B: Polymer Physics 48, 1473-1482 (2010).
4:45 PM - FF6.6/SS10.6
Investigation of Nanomechanical Properties Resulting from the Phase Separation Process in Ultrathin Block Copolymer Films.
Roseanne Reilly 1 , Richie Farrell 2 , Johann De Silva 1 , M. Morris 2 , Graham Cross 1
1 , Trinity College Dublin, Dublin Ireland, 2 , University City Cork, Cork Ireland
Show AbstractBlock copolymer are an important class of emerging advanced materials for nanofabrication. While reducing dimensions to the nanoscale is known to have significant implications for the mechanical properties of homopolymers [1], little is known about the nanoscale mechanics of block copolymers. Here the structural properties and deformation behavior of a diblock copolymer ultrathin film in the glassy state were investigated via a large strain indentation squeeze flow method [2]. This system is of particular interest as, further to the change in mechanical properties due to the straightforward reduction in film thickness, an additional length scale has been superimposed on the system as a direct result of the nature of microphase separation that make block copolymers (BCPs) such a useful material for fabrication. Stress vs. strain measurements of cylindrical indentation volumes in ~ 30 nm thick films were made for both the mixed and phase separated states of a 37k-37k Polystyrene-block-Polymethylacrylate (PS-b-PMMA) diblock copolymer. Measurements of both Polymethylacrylate (PMMA) and Polystyrene (PS) homopolymer thin films of similar molecular weight to the BCP system showed that the BCP system has a consistently intermediate stress-strain response to that of the homogeneous systems, whether phase separated or not. Small strain elastic and elastic-plastic yield properties of the block copolymer were found to be unaffected by phase separation, despite the significant difference between elastic modulus and yield strength of the respective PMMA and PS homopolymers. However at large strains, under conditions of large plastic flow found during nanoimprint processes, the phase separated response diverged from that of the prephase separated system and showed an increased resistance to flow. From the standpoint of models that predict strain hardening scaling with entanglement density [3], a reduction in the entanglement due to the phase separation should result in a decrease in strain hardening, opposite to the results we observe. [1]A. Raegen, M. Chowdhury, C. Calers, A. Schmatulla, U. Steiner, G. Reiter, uuml, and nter, "Aging of Thin Polymer Films Cast from a Near-Theta Solvent," Physical Review Letters, vol. 105, p. 227801, 2010.[2]G. L. W. Cross, B. S. O'connell, J. B. Pethica, H. Rowland, and W. P. King, "Variable temperature thin film indentation with a flat punch," Review of Scientific Instruments, vol. 79, pp. 013904-13, 2008.[3]Boyce MC and H. RN., The physics of glassy polymers vol. The post-yield deformation of glassy polymers. London: Chapman & Hall, 1997.
5:00 PM - FF6.7/SS10.7
Broadband Nanoindentation as a Local Probe for Mechanical Spectroscopy.
Joseph Jakes 1 , Z. Humberto Melgarejo 2 , Amirreza Sanaty-Zadeh 2 , Ken Smith 1 , Rod Lakes 3 , Don Stone 4 2
1 Performance Enhanced Biopolymers, USDA Forest Products Laboratory, Madison, Wisconsin, United States, 2 Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin, United States, 3 Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin, United States, 4 Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractMechanical spectroscopy is the assessment of a mechanical index, such as the viscoelastic Young’s modulus or the plastic flow stress, across a broad spectrum of time scale, deformation rate, or temperature. Materials scientists have long used mechanical spectroscopy to gain insight into defect motion, deformation mechanisms, and strengthening mechanisms, and to assess and predict performance across a wide range of conditions. Our goal is to develop mechanical spectroscopy methods for probing microscopic structures such as thin films, phases in alloys, and the cell wall components in wood. We have invented broadband nanoindentation creep (BNC) to measure viscoplastic properties across 4-6 decades of strain rate and broadband nanoindentation viscoelasticity (BNV) to measures viscoelastic properties across >8 decades of time scale. The measurements require an instrument with fast response that is nevertheless stable against thermal drift. Materials studied include poly methyl methacrylate, polycarbonate, polystyrene, bulk and thin-film molybdenum, Zr-Cu-Al metallic glasses, and Mg-Zn based alloys. BNC experiments generate hardness vs. strain rate. BNC data from polymers are all path-dependent (depending on initial rate of loading). BNC data from molybdenum and metallic glasses are path independent (behavior does not depend on the initial rate of loading). By a simple formula that works for the polymers and molybdenum, the hardness-strain rate data can be converted to flow stress vs. strain rate; and the converted data agree with literature compression data (uniaxial data for the metallic glasses and Mg-Zn alloys are unavailable, so we can not test this formula for these materials, but the BNC results are close based on available literature data). Likewise, BNV data follow the trend of more conventional viscoelasticity measurements made using dynamic mechanical analysis (DMA) and broadband viscoelastic spectroscopy. We perform nanoindentation measurements at temperatures between 5 and 200°C and compare the results with those obtained from conventional mechanical spectroscopy.
5:15 PM - FF6.8/SS10.8
In Situ Tensile Testing of Nanoimprinted Pt-Based Metallic Glass Rods.
Roman Ehrbar 1 3 , Golden Kumar 2 , Jan Schroers 2 , Ralph Spolenak 3 , Daniel Gianola 1
1 Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 3 Department of Materials, ETH Zurich, Zurich Switzerland, 2 Mechanical Engineering, Yale University, New Haven, Connecticut, United States
Show AbstractRecent strategies for developing amorphous metals that exhibit appreciable toughness, in addition to high strength, often involve composite geometries with secondary crystalline phases of submicron sizes. The notion that shear bands, which typically lead to catastrophic failure, can be inhibited or distributed in small confined regions suggests a shift in deformation mechanisms with decreasing size and has led to recent research interest in the mechanical behavior of monolithic amorphous metals in small volumes. Yet, many size dependant studies on the deformation mechanism in amorphous metals have been fraught with uncertainty, primarily because of the potentially deleterious effect of the focused ion beam (FIB) used in specimen preparation on mechanical effect. Since the effect of ion bombardment on the mechanical properties of amorphous specimens in the length scale regime of interest has still not been fully resolved, alternative fabrication and nanomechanical testing routes would allow for a clearer intepretation of intrinsic behavior.We demonstrate a method for in situ testing of amorphous Pt57.5Cu14.7Ni5.3P22.5 nanorods produced by a nanoimprinting approach where the amorphous alloy is heated above its glass transition, infiltrated into a nanoporous alumina template, and subsequently quenched. Individual nanorods were harvested and manipulated onto a novel nanotensile testing system to elucidate the mechanical response of nanorods as a function of size. The custom nanomechanical testing system is based on a six-axis nano positioning device combined with a load cell and a stiff linear actuator, which is integrated in a high resolution scanning electron microscope (SEM). We performed tensile tests on amorphous nanorods with diameters ranging from 100 to 200 nm. The full tensile response of these amorphous rods have been measured, and results showing both elastic and plastic behavior, as well as the propensity for shear banding in small volumes, will be presented. We discuss these results in the context of several theories predicting a transition from heterogeneous to homogenous plastic flow with decreasing specimen size.
5:30 PM - FF6.9/SS10.9
Towards a Comprehensive Approach for Modeling the Freeze Casting Process.
Frank Wendler 1 2 , Marcel Huber 2 , Britta Nestler 2 1
1 Institute of Materials and Processes, Karlsruhe University of Applied Sciences, D-76133 Karlsruhe, Baden-Württemberg, Germany, 2 IAM-IZBS, Karlsruhe Institute of Technology (KIT), Karlsruhe, Baden-Württemberg, Germany
Show AbstractIn the freeze casting process, the crystallization kinetics of an aqueous colloidal solution is exploited to produce filigree porous structures with customizable properties, applicable to a broad variety of ceramic materials with porosities between 10 and 90 vol. %. In the last ten years, great research efforts have been undertaken to optimize the process for biomedical, catalysis and metal-matrix composite applications, especially with regard to mechanical stability of the sintered end product. The patterning effect is based on the rejection of dispersed ceramic particles of an aqueous colloid by the growing ice front. It leads to the formation of domains of parallel lamellae, which can be related to the orientations of the growing crystals.In order to predict quantitatively the influence of the macroscopic and microscopic process variables (freezing conditions, solid fraction, particle size, colloidal interaction potential) on the resulting microstructure, we treat the free boundary problem by adapting a multi phase-field of Allen-Cahn type [1]. Here, a set of order parameters Φ=(Φ1, ..., ΦN) is used to describe the spatio-temporal evolution of the constitutive phases ice, colloidal particles and water, based on a thermodynamic free energy formulation. As a major subsystem, we first concentrate on the crystallization of ice in pure water, for which an expansion of the interfacial free energy and kinetic anisotropy in terms of real spherical harmonics is necessary to produce the observed growth shapes.To be able to run simulations of representative volume elements, the complex problem is separately treated at the particle – ice front scale (< 100 μm) and at a large scale (~ 1000 μm), where the particle density enters as a local solute concentration. For the former case the particles are spatially resolved, and we briefly show how the model parameters (interface tensions, higher order potential, interface width) represent the capillary properties of the colloid. Simulations results show the onset of ice front instability, which are compared to earlier theoretical analysis [2], and the interaction of particles at ice-water triple junctions. For the large scale simulations in 2D and 3D, we first verify the dynamics and morphology evolution in the pure water-ice system with available literature data. Furthermore, for a range of different solid fractions and undercooling temperatures, we compare the simulation data with recent experiments with Al2O3 particles.[1] B. Nestler, F. Wendler, M. Selzer, B. Stinner and H. Garcke, Phys. Rev. E 78 (2008) 011604-1. [2] S.S.L. Peppin, J.S. Wettlaufer and M.G. Worster, Phys. Rev. Lett. 100 (2008) 238301-1.
FF7: Poster Session
Session Chairs
Thursday AM, December 01, 2011
Exhibition Hall C (Hynes)
9:00 PM - FF7.1
Selective Patterning of Self-Assembled Block Copolymer Thin Films by Electron Beam Lithography.
Hiroyuki Suzuki 1 , Reo Kometani 1 , Shin'ichi Warisawa 1 , Sunao Ishihara 1
1 Graduate School of Engineering, The University of Tokyo, Tokyo Japan
Show AbstractThis study describes a method where self-assembled nanostructures of block copolymer are selectively patterned by electron beam lithography. The block copolymer self-assembly is a promising method to fabricate periodic nanostructures such as cylinder in a large area. However, it is still difficult to localize or partially change the morphology of the structures, and therefore applications are limited in scope. We demonstrate that self-assembled nanostructures of block copolymer can be fabricated only in areas patterned by lithography technique.In this study, we fabricated nanoporous structures only in areas exposed by electron beam. We used cylinder forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA; PS 46.1 kg/mol, PMMA 21 kg/mol, diameter of - 20 nm and, pitch of – 40 nm PMMA cylinders are fabricated in a PS matrix) thin films as a resist for electron beam lithography. We fabricated thin films of perpendicularly oriented PMMA cylinders onto a random copolymer modified substrate (PS-random-PMMA; 5.3 kg/mol), the thickness of thin films was 20 ~ 24 nm, and drew line and space (each width is 1 μm) on these films by electron beam lithography. When PS and PMMA were irradiated by electron beam, PS gets crosslinked and PMMA degraded in the exposed areas. After electron beam is exposed, thin films were developed by xylene, which dissolves both PS and PMMA, for 2 min. Therefore, cylindrical nanopores of PS remain only in the exposed areas, while nothing remains in unexposed areas after development. If the electron dose is insufficient, the thickness of the resist residue is small, and nanoporous structures of PS are not observed.We examined the relationship between the electron dose and the thickness of the resist residue after development.At ~ 0.4 mC/cm2: Nothing remained after development.At 0.5 ~ 0.9 mC/cm2: Void lithography pattern was observed, the thickness of the resist residue after development was smaller than that before development and nanoporous structures of PS was not observed.At 1.0 ~ 1.9 mC/cm2: When the electron dose was increased, the thickness of the resist residue after development was increased and nanoporous structures of PS were partly observed.At 2.0 ~ 3.0 mC/cm2: The thickness of the resist residue after development is the same as that before development, nanoporous structures of PS completely remained in the exposed areas and the shape of these structures is the same as the lithography pattern.At 3.1 mC/cm2 ~: Nanoporous structures of PS completely remained, but PS in the unexposed areas remained, too.Therefore, 2.0 ~ 3.0 mC/cm2 is appropriate for PS-b-PMMA resist. It is easy to change the shape of patterned area in this method, and thus we can arbitrarily design the patterns composed of nanoporous structures.In conclusion, we proposed the simple method for fabricating nanoporous structures in selective areas. These structures will be applied to nanodot arrays, nanofilters and photonic devices in future.
9:00 PM - FF7.10
Templateless Micro-nano Patterning of Ring and Line Shapes for Nanomaterials from Solution by a Laser-Induced Micro-Nanobubble on Surface.
Sho Fujii 1 , Ryuta Fukano 1 , Eiro Muneyuki 2 , Masa-aki Haga 1
1 Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, Bunkyo-ku, Tokyo, Japan, 2 Department of Physics, Faculty of Science and Engineering, Chuo University, Bunkyo-ku, Tokyo, Japan
Show AbstractThe emergence of nanostructured materials for functional nanodevices leads to new assembling techniques for the control of the architecture at precise positioning with predetermined number. We have recently reported that a micronanobubble (-1 μm), which was generated by a CW Nd:YAG laser local heating, has allowed to manipulate a single molecule DNA extension and pinning on an Au thin film surface [1, 2]. The mechanism of the manipulation was attributed to both Marangoni convection flow and capillary flow around the micronanobubble. In addition, we found that the accumulation of nanomaterials such as nanoparticles and molecules using the micronanobubble occurred at the substrate/bubble/water three-phase interface, which we will present in this presentation. The present wet method makes it possible to fabricate templateless micro-nano patterns. The assembling experiments were conducted under the inverted microscope (Objective lens 100×/NA 1.30) equipped with Nd:YAG laser (wavelength 1064 nm) and a home-made liquid cell. An Au thin film (10 nm) and an ITO substrates, which can absorb the laser light, were used as the assembling substrate. As a typical example, luminescent CdSe nanoparticles were assembled into a ring shape on the gold surface [3]. The micro-nano ring structure was observed by fluorescence image, AFM and SEM. In the case of Prussian Blue molecules, submicron lines were patterned on ITO substrate using the bubble. The bubble was immediately disappeared when the laser irradiation was stopped. Therefore, this method is easily handled by the laser on - off operation for the formation of a ring and a line patterns, and neither a photomask nor mold is required. In the presentation, we will also discuss the detail of the assembling mechanism around the bubble interface.[1] S. Fujii M. Haga et al., Chem. Lett., 39, 92 (2010).[2] S. Fujii M. Haga et al., Bioelectrochemistry, 80, 26 (2010).[3] S. Fujii, M. Haga, et al., Langmuir, in press (2011).
9:00 PM - FF7.11
Formation and Assembly of Metal Nanoparticles at Gas/Liquid Interface of a Laser-Induced Oscillating Micro-Nanobubble.
Ryuta Fukano 1 , Sho Fujii 1 , Eiro Muneyuki 1 , Masa-aki Haga 1
1 , Chuo University, Tokyo Japan
Show AbstractA bubble in a micro- or nano-meter size has recently attracted considerable attentions because of its remarkable physicochemical properties and broad range of applications. However, there are few reports regarding a chemical reaction around the bubble because of a difficulty to make the stable bubble at the desired place except for a cavitation bubble in the field of sonochemistry. Recently, we have reported a persistent generation of a single micro-nanobubble (∼1 µm diameter) on an Au film surface by a continuous Nd:YAG laser (1064 nm) irradiation in a liquid cell (S. Fujii, et al., Chem. Lett. 2010, 39, 92). In the present study, we examined a formation and an assembly of metal nanoparticles by a chemical reaction around micro-nanobubble at a predetermined position on the gold surface by the Nd:YAG laser. On monitoring the shape of the bubble by a high speed camera (109500 frames per second), the bubble was found to be expanded and contracted spontaneously. That oscillation period was about 20 kHz, which is close to the ultrasonic frequency range. This finding motivated us to apply the oscillating bubble to an on-demand formation and assembly of nanoparticles on the gold surface. When a 1mM [Ag(NH3)2]+ solution was injected into the reaction cell, the formation of submicron-size particles were observed only around the micro-nanobubble at the laser focal point. Under a dark-field microscope, the Ag nanoparticles appeared as various color dots having spectral peaks around 550-600 nm, which corresponds to a plasmon resonance Rayleigh scattering of Ag nano aggregates. As a controlled experiment, a thermal reaction of bulk 100 mM [Ag(NH3)2]+ solution without light irradiation, did not show any plasmon resonance peak of Ag nano particles in UV-Vis spectra. From these results, the formation of Ag nanoparticles occurred at a gas-liquid interface around the bubble. In addition to the formation of nanoparticles by the chemical reaction, the assembling of nanoparticles on the Au surface was observed. With regard to the formation of nanoparticles, we examined various metal ions in aqueous solutions. By use of the chemical species having a redox potential over -0.2V in solution, nano particles were generated around the bubble. These results suggest that the threshold value of the redox potential in the chemical species exists for the formation of nanoparticles.
9:00 PM - FF7.12
Nanoscale Patterning of Vertically Aligned Lead Zirconate Titanate Nanorod Arrays Using Laser Interference Lithography.
Won Hee Lee 1 2 , Young Ho Do 1 , Byeong Kwon Ju 2 , Chong Yun Kang 1 , Seok Jin Yoon 1
1 Electronic Materials Center, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 Display and Nanosystem Laboratory , Korea University, Seoul Korea (the Republic of)
Show AbstractThe development of a facile method for fabricating one-dimensional, precisely positioned nanostructures over large areas offers exciting opportunities in fundamental research and innovative applications. Lead zirconate titanate(PZT) is one of the most widely used ferroelectric materials, due to its excellent piezoelectric and ferroelectric properties. This article presents an effective approach for patterned growth of vertically aligned PZT nanorods (NR) arrays with high throughput and low cost fabrication using laser interference lithography. LIL provides a patterning technology with simple, quick process over a large area without the usage of a mask. Effects of various key parameters for LIL, with 257 nm wavelength laser, are investigated, such as the exposure dosage, the half angle of two incident beams at the intersection, and the power of the light source for generating nanoscale structures. Periodic hole patterns are generated using laser interference lithography on substrates coated with the photoresist. PZT NRs are selectively grown through the holes via a low temperature. Characterization of the PZT naorods by scanning electronic microscopy(SEM) and X-ray diffraction (XRD). These results suggest application possibilities in energy harvesting, sensing and electronic devices.
9:00 PM - FF7.13
The Effect of Nanoscale Contact Stress Field Interactions on Fracture and Deformation of Silicon in Purview of Mechanical Nanofabrication Processes.
Jared Hann 1 , Raul Riveros 1 , Hitomi Yamaguchi 1 , Curtis Taylor 1
1 Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractMechanical nanofabrication methods such as nanoimprinting, scanning probe tip-based nanofabrication, free abrasive machining, etc., provide a viable means of scalable nanostructuring of surfaces with unmatched resolution (< 10 nm). To enable the required accuracy, reproducibility, and precision in process control of these methods it is critical to understand the fundamental deformation and fracture mechanisms that occur at nanoscale (< 100 nm) contacts.In the established indentation fracture model of Lawn and Evans, there is observed a cracking threshold for sharp indenters (Vickers and Berkovich)—below a critical load and contact dimension cracking is suppressed. Using a Vickers indenter, the model predicted a threshold load of 3 mN and contact dimension of 200 nm in Si. The suppression of cracking below the threshold is due to the inablility of the contact-induced tensile stress to reach a critical value for crack propagation. However, we hypothesize that this conventional indentation fracture model may not apply for sharp nanoscale contacts (<100 nm). This is because nanoscale indenters (tip radius (r) < 100 nm) can generate higher concentrated stresses than Vickers indenters. Furthermore, stress concentrations due to subsurface defect pile-up and stress interaction with adjacent contacts are likely to result in fracture below this critical threshold. In this work, we investigate the applicability of the Lawn and Evans indentation fracture model to nanoscale contacts. Systematic nanoindentation fracture experiments are performed on Si(100) using a sharp diamond cube corner (r < 40 nm) indenter as a function of load, number of loads, contact dimension, and contact separation. Atomic force microscopy is used to image and measure contact deformation and fracture. The theory of Henkel transforms used by Sneddon (1948) to solve the equilibrium equations for elastic stresses caused by indentation are applied to qualitatively understand the interaction of adjacent contact stress fields. The experimental results show that the threshold load was decreased to 600 μN. There was observed a consistent increase in depth of second indents from nanoindentation pairs that were separated by small distances (<2 indentation radii). There was an increase in crack length for pairs of indents that were separated by equally small distances (<2 indentation radii). These results supported by recent finite element models in the literature provide an extension of the contact stress model of Lawn & Evans (1977) that takes into account the effect of interacting stress fields from multiple indentations. These results have clear implications for mechanical nanofabrication where stress field interactions impose limits on the closeness (resolution) to which features can be generated and to free abrasive machining where stress field interactions enhance the ability to machine below the threshold load.
9:00 PM - FF7.14
Understanding What Nanoindentation Tells Us about the Mechanical Properties of Confined Polymer Films.
Johann de Silva 1 , Harry Rowland 1 , Roseanne Reilly 1 , Graham Cross 1
1 CRANN/School of Physics, Trinity College Dublin, Dublin Ireland
Show AbstractWe aim to fully understand the mechanical properties of polymeric materials confined in thin films of thicknesses approaching the equilibrium end-to-end distance or radius of gyration (Rg), specifically where these properties are directly probed by flat-punch nanoindentation measurements [1]. Recent nanoindentation data have revealed that typical bulk scaling laws cannot be used to fully describe the observed mechanical properties for simple polystyrene thin films, covering a molecular weight range from approximately 40 to 9000 kDa and thicknesses from 30 to 200 nm, both below and above the glass transition temperature (Tg) [2]. We consider how the role of chain conformation, free volume reduction, hydrodynamic compression and excluded volume interactions can influence properties such as yield stress, and lead to modified dynamics and also atypical governing length scales [3]. For example, when polymeric materials are confined into films of a thickness much less than Rg, it is likely that the polymer chains are less entangled than in the bulk (assuming some equilibrium has been reached, not always the case for spin cast films for instance [4]) leading to modified deformation mechanics both above and below Tg [5], where a typical bulk WLF scaling is observed to break down [2].[1] G.L.W. Cross, B.S. O’Connell, J.B. Pethica, H.D. Rowland, W.P. King. Rev. Sci. Instrum. 79 (2008) 013904.[2] H.D. Rowland, W.P. King, J.B. Perthica, G.L.W. Cross. Science 322 (2008) 720-724.[3] R. Quinson, J. Perez, M. Rink, A. Pavan. J. Mater. Sci. 32 (1997) 1371-1379.[4] G. Reiter, S. Napolitano. J. Polym. Sci. B 48 (2010) 2544-2547.[5] L. Si, M.V. Mass, K. Dalnoki-Veress, H.R. Brown, R.A.L. Jones. Phys. Rev. Lett. 94 (2005) 127801.
9:00 PM - FF7.15
PDMS-Assisted High Aspect Ratio 60nm Large-Area Metal Mold Fabrication for Nanoimprint Lithography.
Rizwan Muhammad 1 , Si-Hyeong Cho 1 , Jung-Hwan Lee 1 , Jin-Goo Park 1 2
1 Bio-Nano, Hanyang University, Ansan, Gyeonggi-Do, Korea (the Republic of), 2 Materials Engineering, Hanyang University, Ansan, Gyeonggi-Do, Korea (the Republic of)
Show AbstractAvailability of durable molds with nanometer-scale features acts as a bottleneck for nanoimprint lithography. Silicon (Si) molds are typically fabricated by electron beam lithography, which is very expensive technology. Previous researches have shown the fabrication of metal molds from Si molds by applying seed layer on Si mold followed by electroforming. After electroforming, Si mold is fully dissolved in KOH to get metal mold. This method is not only time consuming but also results in the loss of costly Si master mold.In this work, improved PDMS and PDMS-assisted nano metal mold fabrication process was demonstrated that does not require the sacrifice of master mold thus making it a viable solution for getting large area high aspect ratio nano-molds for UV- and thermal nanoimprint lithography. Master mold is also completely reusable after replication.Si wafers with patterned area of 80x80mm2 with features ranging from 60nm to 2um and with aspect ratio of upto five in nanochannel areas were used as mother mold for replication process. Patterned Si wafer was treated with vapor self-assembled monolayer (V-SAM) that acts as an antistiction layer during separation process. This V-SAM treated Si wafer was used as a master mold for making PDMS nano mold. PMDS is a high viscosity material and it is challenging to fill the high aspect ratio nano features during PDMS casting. Toluene was used as a solvent to decrease the viscosity of PDMS and to fill the nano features in the master mold. PDMS nano-mold replication process was optimized by testing various concentration of toluene in PDMS. This large area PDMS mold can be used as a stamp for UV-Nanoimprint lithography that requires transparent molds. In next step, this PDMS mold was used as a master for electroforming high aspect ratio CoNi nano-mold. For this purpose, thin seed layer was applied on PDMS mold for conduction purpose followed by 300µm thick CoNi electroforming in chloride bath. It was found that CoNi mold can be successfully prepared by electroforming on PDMS mold and flexible nature of PDMS helps a great deal in separation of the two molds after electroforming. Residual stresses in electroformed mold must be minimized to obtain distortion free mold. In CoNi electroforming, residual stresses were found to be highly dependent on anode-to-cathode distance in the bath and stress nature was changed from compressive to tensile when anode-to-cathode distance was gradually increased. It was found that distortion-free CoNi mold could be electroformed by choosing a suitable anode-to-cathode distance as well as flow-rate of electrolyte.FE-SEM, 3D Profiler and AFM were used to characterize replicated PDMS and CoNi nano molds as well as Silicon master.
9:00 PM - FF7.16
Novel One Step Encapsulation with Hydrogen-Bonded Layer-by-Layer Assembly Using Printing Techniques.
Rattanon Suntivich 1 , Olga Shchepelina 1 , Ikjun Choi 1 , Vladimir Tsukruk 1
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractUsing printing techniques, we present a new approach for encapsulation based on hydrogen-bonded polymeric LBL films. We are able to encapsulate a dye inside poly(vinylpyrrolidone) /poly(methacrylic acid) (PVPON/PMAA) LBL structures without requiring a washing step. One step encapsulation improves encapsulation efficiency, processing time, structure patterning, ability to control capsule size, and diffusion rate. With PVPON/PMAA LBL assembly based on hydrogen-bonding interactions, the capsules are stable in acidic solution such as pH 3.5 and rapidly dissolved in basic solution at pH 8.0 to release encapsulant as a result of hydrogen bond breaking. AFM images provide a greater understanding in the chain conformation of PVPON/PMAA LBL assembly from printing techniques and demonstrate different molecular conformations for various polymer concentrations and numbers of multilayer.
9:00 PM - FF7.17
Hollow Vertical Metallic Nanocylinders via NIL.
Binod Rizal 1 , Stephen Shepard 1 , Michael Burns 1 , Thomas Chiles 1 , Michael Naughton 1
1 , Boston College, Chestnut Hill, Massachusetts, United States
Show AbstractWe have used nanoimprint lithography to fabricate arrays of hollow vertical metallic nanocylinders. The fabrication process begins with arrays of NIL-fabricated SU-8 polymer replicas of silicon nanopillars. The nanocylinder array is formed by metalizing the polymer pillars, followed by mechanical polishing to remove the tops of the pillars and reactive ion etching to remove SU-8 cores. This leaves the outer cylindrical metal film as a self-supporting cylinder. Arrays of sub-wavelength diameter (e.g. 200 nm) cylinders introduce a nanoplasmonic platform merging multiple modalities for optical trapping, nanospectroscopy, sensing applications, etc. We will discuss the details of the fabrication process of these arrays as well as their physical and optical properties.
9:00 PM - FF7.18
Understanding High Field Chemistry in Scanning Probe Nanostructure Direct Write.
Stephanie Vasko 1 2 , Wenjun Jiang 3 4 , Renyu Chen 3 , Scott Dunham 3 , Marco Rolandi 1
1 Materials Science and Engineering, University of Washington, Seattle, Washington, United States, 2 Chemistry, University of Washington, Seattle, Washington, United States, 3 Electrical Engineering, University of Washington, Seattle, Washington, United States, 4 Physics, University of Washington, Seattle, Washington, United States
Show AbstractAtomic force microscope direct write can create semiconductor features with nanoscale resolution, as well as deterministic placement and geometry control, by reacting metalloorganic liquid precursors with a biased (ca. 12 V) AFM tip. Using diphenylgermane and diphenylsilane, carbon-free germanium and silicon nanostructures (SIMS, x-ray PEEM) can be fabricated. We propose a model that involves electron capture and precursor fragmentation in this unique high field (10^9 V/m) nanoscale environment. To verify this theory, experimental data and simulations are used to elucidate the chemical reactions occurring near the tip–sample interface during high field chemistry of diphenyl group IV semiconductors. Current data during writing and bias dependent growth rate are analyzed, supplemented with data from ionization mass spectrometry, and compared with the simulation results. Future work on substrate effects on reaction kinetics will also be discussed.
9:00 PM - FF7.2
Ferroelectric Nanodot Formation in Spin Coated Poly (Vinylidene Fluoride-trifluoroethylene) Films.
Yoonyoung Choi 1 , Moonkyu Park 1 , Jongin Hong 2 , Kwangsoo No 1
1 , Department of Materials Science and Engineering, KAIST, Daejeon Korea (the Republic of), 2 , Department of Chemistry, Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractFerroelectric and piezoelectric nanostructures have attracted much interest for potential application in miniaturized sensor arrays, actuators and non-volatile memory storage devices. Among various ferroelectric materials, poly(vinylidene fluoride–trifluoroethylene) P(VDF–TrFE) is a good candidate material for ferroelectric nanodevices because of its large remnant polarization, short switching time and good thermal stability. Other advantages of this ferroelectric polymer include high flexibility, low weight, inexpensive processing techniques, and easy modification of shape and size.P(VDF–TrFE) nanodots were fabricated by spin-coating and post-annealing processes. The P(VDF-TrFE) pellets in a molar ratio of 75/25 were dissolved in methyl ethyl ketone (MEK). To investigate the effect of thickness on the dot morphology, solutions with concentrations in the range 3 wt% to 0.25 wt% were prepared by sonication. Subsequently, polymeric films were deposited on the Au/Ti/Si substrates by a spin-coating technique and annealed at 150°C for 2 hours. To confirm the formation of dot structures and the existence of ferroelectricity in P(VDF-TrFE) dot structures, they were analyzed by fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM) and piezoresponse force microscopy (PFM). In this study, we used a simple spin-coating technique to fabricate and characterize self-assembled P(VDF-TrFE) nanodots. Importantly, the P(VDF–TrFE) nanodots showed a higher concentration of β-phase [F(β) < 54%], than the P(VDF-TrFE) films [F(β) = 51%] reported in the literature. P(VDF–TrFE) nanodots of 51.4 ± 10.6 nm in height and 172.75 ± 40.5 nm in diameter displayed superior piezoresponse values (18.1 ± 3.3 pm/V) and a low coercive voltage (2.4 ± 0.5V). The P(VDF–TrFE) nanodots may be applied in nanostructured devices such as high density non-volatile memory devices and infrared sensor arrays.
9:00 PM - FF7.20
AFM High Field Nanolithography with a Gold Deposition Precursor.
Matteo Lorenzoni 1 , Bruno Torre 1
1 Nanophysics, Italian Institute of Technology, Genova Italy
Show AbstractUsing AFM for nanofabrication is a very attractive field of research, AFM nanolithography has shown itself to be a unique tool for materials structuring and patterning with nanometer precision. Considering bias-assisted AFM nanolithography techniques, a great potential is offered by the use of organo-metal precursors used in CVD (Chemical Vapour Deposition) as deposition precursor that can decompose under the high electric field created in the tip-sample contact region as demonstrated for other organometals [1] .The main goal of the research project is to realize high field AFM lithography with a gold deposition precursor such as metal alkyl (diketonate) complexes, thus fabricating high purity gold controlled nanostructures on Si wafers. The fabrication technique developed can be later on employed in target application like the creation of gold nanofeatures on a precise identified area that overlaps the focus of pre-fabricated plasmonic lenses. The advantages of such technique in comparison with other well established fabrications techniques (i.e. EBL) are the high purity of metal deposed, the non-destructive real time imaging given by AFM and the easy positioning on pre-fabricated structures. Such a versatile technique allows for a multi step approach based on a sequence of different precursors (i.e. organo-silver) to depose different metal on target substrates.At present the project is its early stages with promising results regarding the instrumental setup and the chemical – physical characterization of precursors and substrates involved. [1] Jessica D. Torrey, Stephanie E. Vasko, Adnan Kapetanovic, Zihua Zhu, Andreas Scholl and Marco Rolandi, Advanced Materials Volume 22, Issue 41, November 2, 2010, Pages: 4639–4642
9:00 PM - FF7.21
Nanoscale Fabrication of the Ferroelectric Polymer Poly(Vinylidene Fluoride with Trifluoroethylene) P(VDF-TrFE) 75:25 Thin Films by Atomic Force Microscope Nanolithography.
Omar Vega 1 , David Delgado 1 , Freddy Wong 1 , Rosette Gonzalez 1 , Luis Rosa 1
1 Physics and Electronics, University of Puerto Rico - Humacao, Humacao, PR, Puerto Rico, United States
Show AbstractThin films of the only organic ferroelectric system, poly(vinylidene fluoride with trifluoroethylene) P(VDF-TrFE) 75:25 layers have been deposited on Highly Order Pyrolytic Graphite (HOPG) and Silicon Dioxide (SiO2) by the horizontal Schaefer method of Langmuir-Blodgett (LB) techniques. It is possible to “shave” or mechanically displace small regions of the polymer film by using Atomic Force Microscope Nanolithography techniques such as nanoshaving, leaving swaths of surface area cut to a depth of 4 nm and 12 nm exposing the substrate. The results of fabricating stripes by nanoshaving two holes close to each other, shows a limit in “stripes” widths of average 153.29 nm and 177.67 nm that can be produced. Due to the lack of adhesion between the substrates and the polymer film P(VDF-TrFE) smaller “stripes” of P(VDF-TrFE) cannot be produced, it can be shown by the sequencing of nanoshaved regions, “stripes” of thin films can be removed.
9:00 PM - FF7.22
Fabrication of Modular Metallic Nanostructures by Dip-Pen Nanolithography.
Sandra Gilles 1 , Michael Noyong 1 , Ulrich Simon 1
1 Institute of Inorganic Chemistry, RWTH Aachen University, Aachen Germany
Show AbstractThe permanent demand for increased performance and efficiency of electronic and sensor devices results in ongoing miniaturization of the components as well as in the development of new device concepts. Both top-down and bottom-up approaches are utilized for this purpose. Metallic nanoparticles or clusters are easily prepared nanoscale building blocks which appear as well-defined functional units in this context, e.g. for the use in single electron transistors [1]. For such applications it is required to assemble nanomaterials on a surface in a defined pattern and to electrically address functional units. Here we present the fabrication of modular metallic nanostructures by dip-pen nanolithography (DPN). Dip-pen nanolithography is known as a patterning technique based on scanning probe methods [2]. A material ("ink") is transferred ("written") by an AFM tip ("pen") to an appropriate substrate. The method bears the potentials of high resolution, user-defined patterning, and, by using parallel pen arrays, high throughput. Using DPN we first build planar gold structures by writing alkane thiols on sputtered gold layers. The patterned thiol monolayers are used as mask in a subsequent wet chemical etching step [3,4] by which unprotected gold areas are removed. In this manner we create gold nanoelectrodes that exhibit good electrical conductivity and provide high flexibility for electrical addressing of nanoscale functional units. Furthermore we demonstrate patterned modification of silicon dioxide surfaces with amino terminated silane layers via DPN. These chemical templates guide the self-assembly of gold nanoparticles. By this means nanoparticles can be positioned precisely into almost every type of nanoelectrode configuration without exposing the delicate nanomaterial to harsh lithography conditions that might harm particle size and shape, crystal structure or ligand shell. [1] G. Schmid and U. Simon, Chem. Commun., 2005, 697-710[2] R. D. Piner, J. Zhu, F. Xu, S. Hong, C. A. Mirkin, Science, 1999, 283, 661-63[3] Y. Xia, X.-M. Zhao, E. Kim, G. M. Whitesides, Chem. Mater., 1995, 7, 2332-37 [4] M. Zhang, S.-W. Chung, C. A. Mirkin, Nano Lett., 2003, 3, 43-45
9:00 PM - FF7.23
Large-Scale Fabrication of PZT Nanowires for Energy Conversion and Interfaced Neuronal Nanomechanics.
Thanh Nguyen 1 , Michael McAlpine 1
1 MAE, Princeton, Princeton, New Jersey, United States
Show AbstractThe development of a facile method for fabricating one-dimensional, precisely positioned nanostructures of complex metal oxides over large areas offers exciting opportunities in fundamental research and innovative applications. Large-scale nanofabrication methods have been restricted in accessibility due to their complexity and cost, while bottom-up synthesis of nanowires has been limited in methods to assemble these structures at precisely-defined locations. Piezo-nanomaterials such as PbZrxTi1-xO3 (PZT) nanowires – which may be useful for highly efficient nanoscale power generation – are difficult to synthesize without suffering from polycrystallinity or poor stoichiometric control. Here, we report a novel fabrication method which requires only low resolution photolithography to generate ultra smooth, high performance PZT nanowires over wafer scales. Indeed, local probing of the nanowires shows achievable piezoelectric charge constant of d33 ~ 145 pm/V. The achievement of high performance PZT nanostructure is not only significant for electronic power conversion applications but also in the field of biomedical sensing. Specifically, piezoelectric nanowires offer a unique property to locally probe and detect minute mechanical deformations of neuronal membrane associated with cell membrane depolarization or action potential. In order to exploit the materials, a highly sensitive PZT nanoribbon cantilever-like structure was fabricated. Following that, a biocompatible interface between the cantilever arrays and neuron cells was developed, in which the piezo-nanocomponents serves as a platform for recording and characterizing mechanical properties of neuron cells in a sensitive and spatially resolved manner. This achievement of highly functional piezo-nanomaterials could yield breakthroughs in areas ranging from nanodevice array biosensing to nanodevice powering.
9:00 PM - FF7.25
Meniscus-Guided Three-Dimensional Writing of Conducting Polymer Nanowire Arrays.
Ji Tae Kim 1 , Seung Kwon Seol 2 , Jaeyeon Pyo 1 , Ji San Lee 1 , Jung Ho Je 1 , G. Margaritondo 3
1 Materials science and engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 Medical & IT Convergence Research Division, Korea Electrotechnology Research Institute (KERI), Ansan Korea (the Republic of), 3 Faculté des Sciences de Base, Ecole Polytechnique Fédérale, Lausanne Switzerland
Show AbstractOrganic electronics increasingly impacts our everyday life with a variety of devices such as displays for TV or mobile appliances, smart cards and radio-frequency identification (RFID) tags(1). This blossoming domain could greatly profit from effective ways to fabricate conducting or semiconducting organic nanowires (2). Specifically, the three-dimensional (3D) and individual integration of each nanowire is essential (3) for many new device concepts, but so far this was not possible. Here we show the demonstration of accurate and versatile 3D direct writing of conducting polymer nanowires based on guiding a monomer meniscus by pulling a micropipette during oxidative polymerization (4). By modifying the pulling speed, the wire radius is accurately controlled down to ~ 50 nm. We specifically demonstrate the realization of well-defined dense arrays of various freestanding nanocomponents: straight wires, nanowires with variable radius, branches, and bridges, which is unfeasible by previous direct ink writing or drawing methods. The individual components are positioned with an accuracy of 250 nm and the electrical transport properties are independently controlled for each nanocomponent. The practical use of the technique is tested by producing nano-arches functioning as individually addressable photo-switches. Our results demonstrate in a broader prospective the 3D integration of individually addressable organic nano-components for organic nano-devices. This is an important step for organic electronic integration with high density and enhanced freedom in circuit design.*Email:
[email protected];
[email protected] References(1) S. R. Forrest, Nature 428, 911 (2004).(2) A. L. Briseno et al., Mater. Today 6, 3 (2007).(3) B. Tian et al., Science 329, 830 (2010).(4) J. T. Kim et al., Adv. Mater. 23, 1968 (2011) [Inside front cover]
9:00 PM - FF7.26
Template-Based Approach for the Synthesis of 2D/3D Nanostructures.
Cigang Xu 1 , Qi Fang 1 , Robert Gunn 1 , Chris Hodson 1 , Mike Cooke 1
1 , Oxford Instruments Plasma Technology, Bristol United Kingdom
Show AbstractThe template-based approach has been used for the synthesis of nanomaterials with the potential application in the green energy and other fields. The templates are AAO and carbon nanotubes, with which the inner hollow space and the external contour is used respectively. Both the plasma enhanced chemical vapour deposition (PECVD) and Atomic Layer Deposition (ALD) processes have been studied for various materials, including SiO2 and Al2O3. It is found that the resulting materials are related to template and materials to be synthesized, as the size of the template can affect the morphology of nanostructures obtained. Moreover, the comparison between PECVD and ALD processes shows that the growth through ALD processes can result in more control on the dimension of nanostructures than that of PECVD processes as the smaller space of the template can be reached during ALD processes. This can be explored to develop 2D and 3D nanostructure of the intended materials for their application in solar cells and other devices.
9:00 PM - FF7.27
Pore Size Dependence of 3D Anodic Alumina SERS Substrates.
Zachary Combs 1 , Rajesh Kodiyath 1 , Sehoon Chang 1 , Maneesh Gupta 1 , Richard Davis 1 , Vladimir Tsukruk 1
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractIn order to increase the sensitivity of SERS devices, interest has been shown in the development of 3D substrates to improve upon the typically modest enhancement factors of commercially available 2D substrates. We have demonstrated clear experimental evidence that shows the strong dependence of the SERS activity of 3D anodic alumina substrates on the diameter of the membrane pores. Porous anodic alumina membranes were synthesized via a two-step anodization process with pore sizes ranging from 98 to 355 nm. Silver nanoparticles were then bound to the interior of the pores by the electroless deposition of silver seeds and their subsequent growth into 30 ± 5 nm particles. Using standard Raman markers, Rhodamine 6G and benzenethiol, it was shown as pore diameter increased, the SERS activity of the substrate also increased, with the 355 nm substrate showing a near record enhancement factor of 1010 for benzenethiol. This study can provide insight into the design of future 3D SERS substrates composed of porous media.
9:00 PM - FF7.3
Super-Hydrophobic Silicon Surface with Micro/Nano Composite Structure Formed by Simple Wet Etching.
Takatoshi Yasui 1 , Tsuyoshi Sueto 1 , Kensuke Nishioka 1
1 , University of Miyazaki, Miyazaki Japan
Show AbstractWater-repellent silicon (Si) surface with nanostructure was formed by simple wet chemical etching using hydrofluoric acid (HF) and nitric acid (HNO3). Water-repellent surfaces are of considerable interest for various technological applications. Surface wettability is determined by the chemical composition (surface free energy), surface geometric microstructure, and surface cleanliness. Water repellency can be increased by forming micro or nanostructures. Advances in nanotechnology, including micro/nano-electromechanical systems (MEMS/NEMS), have stimulated the development of new materials and design of surfaces which should have water-repellent surfaces with low adhesion and friction. Therefore, it is necessary to develop simple processing methods for the formation of water-repellent fine structures.Single-crystalline Si(100) was used as a substrate. As a first step, a micron size pyramid structure was formed by commonly used alkaline etching. Next, the sample was soaked in an aqueous etching solution of HF and HNO3 with volume ratio HF(50%) : HNO3(60%) : H2O = 11 : 1 : 3. By the acid etching, a nano size structure was formed on the micro size pyramid structure. Etching time was varied from 10 to 22 sec. By the 2 step etching method, a micro/nano composite structure was formed.The contact angle was measured using a contact angle measurement system (G-1-1000, ERMA INC.). The Si surface with micro/nano composite structure had contact angle of 167o, indicating a water-repellent surface, whereas the surface without nano structure (only micron pyramid structure) had contact angle of 111o. By using this technique, the water-repellent structure on Si can be formed without costly system.
9:00 PM - FF7.4
Altered Traction Forces and Cellular Responses of Breast Cancer Cells on Polyacrylamide Hydrogels with Nano Patterns.
Yongchen Wang 1 , Lijuan Zhang 1 , Jennet Toyjanova 2 , Thomas Webster 2 , Christian Franck 2
1 Department of Chemistry, Brown University, Providence, Rhode Island, United States, 2 School of Engineering, Brown University, Providence, Rhode Island, United States
Show AbstractThe mechanical interactions between cells and substrates have drawn a large amount of interest in understanding how to either promote or minimize cell functions. Fundamental experiments aimed at this issue are to measure both cellular traction forces and subsequent cellular responses. Polyacrylamide (PA) hydrogels, as a promising elastic substrate, can facilitate both of these measurements because of its inherent properties, such as recoverable and linear deformation responding to cellular forces, tunable stiffness according to the amounts of cross-linker bis-acrylamide added, capability of adsorbing proteins, desirable optical properties for microscopy evaluation and so on. However, to date, few have investigated the role that nano surface feature patterns in PA hydrogels have on cancer cell responses. In this study, nano patterns of different sizes were made on the surface of the PA hydrogels and these nano patterns were shown to decrease cancer (breast and lung) cell functions including adhesion, proliferation, and VEGF synthesis (a key growth factor which promotes angiogenesis in tumors). To further such research, the objective of this study was to further explore if mechanical interactions between cells and PA gels are altered due to nanostructured surface features which may help to explain their reduced behavior on such substrates. PA hydrogels with fluorescent beads were prepared through standard techniques. The nano patterns were created by first fabricating a mold consisting of the self-assembly of polystyrene microspheres with diameters of 27 nm, 300 nm and 400 nm. Then, the nano patterns were replicated onto the surface of the poly(dimethylsiloxane) (PDMS) molds during a polymerization process. A PDMS mold with a smooth surface was also synthesized as controls. The polymerization process of PA hydrogels was initialized by the exposure to ultraviolet light and the stiffness of the hydrogels was controlled by the exposure time of the ultraviolet light. So according to three different periods of UV light exposure, three groups of hydrogels with nano patterns of the same size will have different stiffness and their results compared. The roughness of the hydrogels were characterized by AFM and SEM. Contact angle assays were also carried out. Moreover, breast cancer cells and the breast healthy cells were cultured onto the various PA hydrogels and fluorescence confocal microscopy was utilized to test the traction forces between the hydrogels and the cells and the subsequent cellular responses of the cancer cells and healthy cells. Initial findings show altered cancer cell responses on the PA nano patterns and the stiffness of the hydrogels on their mechanical interactions. Such results are useful to further understand how to minimize cancer cells responses.
9:00 PM - FF7.5
Enabling Lithographic Patterning on Curved Nanostructures by Self-Assembly.
Teena James 1 , Jeong-Hyun Cho 1 , David Gracias 1
1 , Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractWhile it is relatively straightforward to pattern planar substrates using nanolithographic methods, it is extremely challenging to incorporate lithographically defined patterns on curved nanostructures. We describe a methodology to curve nanostructures by inducing grain coalescence in tin (Sn) thin films, post-deposition. The structures assemble spontaneously during plasma etching of lithographically patterned metallic or dielectric Sn constituted bilayer thin films. The utilization of this strategy in combination with planar nanolithographic methods enables the creation of simultaneously patterned and curved nanostructures. We will discuss curving of both electron (e) beam and nanoimprint lithography patterned samples to realize wafer-scale parallel assembly of simultaneously curved and lithographically patterned nanostructures for applications in electronics, optics and biomedical engineering.
9:00 PM - FF7.6
Large Scale SWCNTs Assembly Using Template Guided Fludic Assembly.
Jungho Seo 1 2 , Jun Huang 2 , Sivasubramanian Somu 2 , Ahmed Busnaina 1 2
1 Mechanical Engineering, Northeastern University, Boston, Massachusetts, United States, 2 NSF Center for High-rate Nanomanufacturing, Notheastern University, Boston, Massachusetts, United States
Show AbstractCarbon nanotube based electronics has attracted intensive research interest due to its excellent electrical and mechanical properties such as high electron mobility, large current carrying capability, and unique one-dimensional nanostructure. We have employed fluidic assembly process to assemble and integrate SWCNTs (Single-Walled Carbon Nanotubes) on lithographically patterned templates by utilizing the various fluidic forces involved. It is critical to control the orientation and dimensions of the SWCNTs assembly for specific applications in the field of biotechnology, electronics, structured materials, and energy storage.Humidity of the environment during assembly process plays a key role on the assembly of SWCNTs. To the best of our knowledge it has not been investigated in great detail. The influence of humidity on template guided fluidic assembly of horizontally aligned SWCNTs has been studied. It is important to control the humidity because the mechanism of fluidic assembly uses the capillary effect of the SWCNTs solution to assist the assembly of SWCNTs into desired regions of the templates. A controllable drying process has been developed to increase the yield of highly dense SWCNT assembly over large arrays.A 1µ thick thermally oxidized silicon dioxide (SiO2) on a 3-inch silicon (Si) wafer was used as a substrate. Conventional piranha (H2SO4:H2O2 = 4:1) cleaning process was used not only to clean organic residues off substrates but also to hydroxylate the surfaces making them hydrophilic. Following that electron-beam resist was spun and patterned by electron-beam lithography. After development the template is dipped into a SWCNTs Solution and is withdrawn gradually at a constant rate (0.05mm/min). The exposed SiO2 hydrophilic surface has hydroxides chemical groups so that it enables the SWCNTs to be anchored directly during the fluidic assembly process. SWCNTs have been assembled on this topographically patterned template substrates over millimeter length scale. Metal electrodes were fabricated on the assembled SWCNTs employing electron-beam lithography and electron-beam evaporation. Electrical characterization of these highly aligned SWCNTs revealed that they exhibit resistivity of the order of 10^-4 ohm-cm suitable for a variety of applications including solar cells and EMI shielding.
9:00 PM - FF7.7
Capillary-Assisted Dielectrophoresis as an Innovative Protocol to Align Nanowires at Single-Level.
Maeva Collet 1 2 , Sven Salomon 1 2 , Florent Seichepine 1 2 , Yannick Coffinier 3 , Philippe Caroff 3 , Christophe Vieu 1 2 , Liviu Nicu 1 2 , Guilhem Larrieu 1 2
1 , LAAS-CNRS, Toulouse France, 2 , Université de Toulouse, Toulouse France, 3 , IEMN-CNRS, Lille France
Show AbstractResearches in nanotechnology are progressively shifted from fundamental studies to functional demonstrators such as, for example, the nanoprocessor based on nanowire circuits proposed by Lieber group [1].This tri-dimensional architecture highlights the great potential of semiconducting nanowires in the coming years as promising/future 3-D nanoscale building blocks to create devices with higher performances, ultrahigh sensitivity biosensors [2] or optoelectronic devices [3].Semiconducting nanowires are synthesized by a bottom-up approach which provides high-quality structures made of tunable materials. However, making a viable technology based on these nano-objects requires the ability to precisely locate them at large scale using a low-cost and reproducible process. One major challenge is to develop a generic alignment method to integrate nanowires for further characterizations or innovative applications. Different techniques such as Langmuir-Blodgett technique or dry-transfer printing have been proposed but single-nanowire alignment cannot be reached easily. That’s why dielectrophoresis (DEP) assembly has received a particular attention: Smith et al. [4] proved that a non-uniform electric-field applied between interdigitated electrodes induces a polarization on dielectric particles such as nanowires. The resulting force localizes the nanowires on predefined electrodes at specific locations. More recent studies [5] [6] showed the potentiality of this approach but some limitations rise up: Raychaudhuri et al. [5] didn’t isolate nanowires from the DEP electrodes which is a great limitation for further applications whereas Freer et al. [6] coupled DEP with a flow-assisted alignment which requires a whole microfluidic cell coupled with a precise control of flow rate. We propose here an innovative method based on capillary-assisted dielectrophoresis to reach addressability of single nanowires at wafer scale. We developed a dedicated process to isolate DEP electrodes from the aligned nanowires based on a planarization method by using a spin-on-glass insulating layer. Thanks to optimized structures, we achieved high-yield alignment of single nanowires based on different materials (Si, InAs…). Once the nanowires are located at desired positions, post-processing can be performed either to provide electrical measurements or to design functional devices.[1]H. Yan et al., Nature, Vol. 470, Feb. 2011, pp. 240-244.[2]K. I. Chen et al., Nano Today, Vol. 6, March 2011, pp. 131-154.[3]P. Yang et al., Nano Letters, Vol. 10, Apr. 2010, pp. 1529-1536.[4]P. A. Smith et al., Applied Physics Letters, Vol. 77, No. 9, Aug. 2000, pp. 1399-1401.[5]S. Raychaudhuri et al., Nano Letters, Vol. 9, No. 6, Jun. 2009, pp. 2260-2266.[6]E. M. Freer et al., Nature Nanotechnology, Vol. 5, Jun. 2010, pp. 525-530.
9:00 PM - FF7.9
Photopatternable Block Co-Polymers for Laser Interference Lithography.
Taiwo Alabi 1 , Dajun Yuan 2 , Suman Das 2
1 Material Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Mechanical Engineering, Georgia Institute of technology, Atlanta, Georgia, United States
Show AbstractLaser Interference lithography (LIL) is a robust, relatively inexpensive, and high throughput process for generating periodic micro- and nanoscale structures over large areas on substrates, with the periodicity of features dependent on several parameters and given by the equation: P=λ÷(2n Sin θ), where λ is the wavelength of light beam source, n is the dielectric constant of the medium and 2θ is the angle between the two interfering beams. Block co-polymer phase separation (BCPS), on the other hand, can generate micro-domains with feature type and periodicity dependent on chain length, degree of polymerization, polymer-air and polymer-substrate interaction, annealing environment and solvent, the Flory-Huggins interaction parameter, temperature etc. For block co-polymers under the strong segregation limit and using the self-consistent mean field theory approximation, the inter-domain spacing is given by the general formula: d ~ α N^δ χ^ν, where N is the degree of polymerization of the block, χ is the Flory-Huggins interaction parameter, α is the statistical segment length, and δ,ν are the scaling parameters. The combination of LIL and BCPS techniques, with phase-separated block co-polymers serving as functional photoresists could potentially lead to an inexpensive, robust means of generating hierarchical features on substrates with increased feature density.We report here for the first time on the LIL patterning of as-spun block co-polymer thin films on silicon substrates. Our process involves the use of a 10ns pulsed Nd:YAG laser light source with 266 nm wavelength and a PS-P4VP or PS-PEO block copolymer as a positive photoresist. Through this approach, secondary domains with periodicity ranging from 250 nm to 2µ are generated via control of angle between the interfering beams, and the laser intensity while the primary ordering within the block co-polymers was constant but could be varied easily by changing the volume fraction of either of the blocks amongst other methods. The choice to go with PS-P4VP and PS-PEO is due to reported selective complex formation between the P4VP and PEO component and several metallic salts: however, this does not exclude the use of other diblock or triblock copolymers having a component that selectively bonds to a metallic salt, or a block copolymer having an intrinsic metallic or nonmetallic component. Equations for calculating feature densities of laser-patterned block co-polymer thin films in the SSL regime are also proposed. The characterization of as-spun and laser-patterned block co-polymer thin films was conducted using AFM, SEM and XPS surface characterization techniques. This solvent-free method is robust, and when combined with the nanoscale periodicity in block co-polymers, can produce hierarchical patterns on substrates with potential use in the electronics and semiconductor industries.
Symposium Organizers
Graham Cross Trinity College
Andre Schirmeisen University of Muenster
Armin Knoll IBM Research-Zurich
Marco Rolandi University of Washington
FF8: Mechanical Instability and Beam Based Assembly Techniques
Session Chairs
Costas Grigoropoulos
Shu Yang
Thursday AM, December 01, 2011
Room 202 (Hynes)
9:30 AM - **FF8.1
Nano-/Microfabrication via Pattern Transformation of Periodically Structured Polymers.
Shu Yang 1
1 Materials Science and Engineering, Univ of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractMechanical instabilities in soft materials, precipitated by dewetting, swelling, and buckling are often viewed as failure mechanisms that can interfere with the performance of devices. Nature, on the other hand, provides many examples where instabilities, packing constraints, and simple geometries drive the formation of delicate, detailed, and beautiful patterns. Here, I will discuss pattern evolution and transformation in 2D and 3D periodic porous membranes due to osmotic pressure, capillary force and shape memory effect, respectively. In each system, we compare the experiments with theoretical modeling to elucidate the mechanisms of mechanical instability in different soft materials systems, including elastomeric poly(dimethylsiloxane) (PDMS), responsive poly(2-hydroxy ethyl methacrylate) (PHEMA) based hydrogels, photoresists, and shape memory polymers (SMPs). Finally I will illustrate applications, such as nanomanufacturing and tunable display.
10:00 AM - FF8.2
Wrinkling and Creasing Induced by Catalyst Segregation during Polymerization.
Bryan Vogt 1
1 Polymer Engineering, University of Akron, Akron, Ohio, United States
Show AbstractWrinkled structures have commonly been produced by mechanical stretching of UV-ozone or O2 plasma treated PDMS. Complex pattens can be formed by patterning of the oxidation layer. However, these wrinkles are typically limited to surfaces of very compliant polymers. In this work, we demonstrate the formation of wrinkles by the polymerization of a liquid on hard surfaces. By selecting a catalyst that strongly surface segregates, the relative polymerization rates near the free surface and the bulk are significantly different such that a rigid skin forms on the polymerizing liquid. Contraction of the bulk during further polymerization induces sufficient stress for the surface to wrinkle or even crease depending upon the polymerization conditions. Additionally by using a photoinitiator, the wrinkled areas can be patterned; the shape of the exposed areas can be used to control the wrinkle orientation.
10:15 AM - FF8.3
Phase Field Simulation of Patterning Surface Microstructures through Multiple Stress-Driven Instabilities.
Yong Ni 1 , Qui Pan 1
1 of Modern Mechanics, CAS Key Laboratory of Mechanical Behavior and Design of Materials,, Hefei, Anhui, China
Show AbstractRecent experiments demonstrate the capability of manipulating stress-driven buckling instability for creating complex surface morphologies. When the compressive stress in the film is mediated by diffusion, the buckling instability becomes timely and spatially dependent. In the presence of the film-substrate adhesion, the buckling instability is confined and the resultant film morphology develops into either wrinkles or wrinkle-delamination. In this talk a continuum model integrating phase field microelasticity and von Karman plate theories is proposed to investigate the effect of diffusion process and film-substrate adhesion on the morphological evolution of a compressed thin film on soft substrates. Numerical simulations based on the model reported a rich variety of film morphology. The mechanism and formation of these morphologies are discussed.
11:00 AM - **FF8.4
Laser-Assisted Nanoprocessing and Growth of Semiconductor Nanostructures.
Sang-Gil Ryu 1 , David Hwang 1 , Eunpa Kim 1 , Jae-Hyuck Yoo 1 , Bin Xiang 1 2 4 , Oscar Dubon 2 3 , Andrew Minor 2 4 , Costas Grigoropoulos 1
1 Mechanical Engineering, University of California, Berkeley, California, United States, 2 Materials Sciences and Engineering, University of California, Berkeley, California, United States, 4 National Center of Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractRecent research results will be presented. Lasers of different pulse durations and wavelengths have been coupled to near-field-scanning optical microscopes (NSOMs) through apertured bent cantilever fiber probes as well as with atomic force microscope (AFM) tips in apertureless configurations. Experiments have been conducted on the surface modification of metals and semiconductor materials. By combining nanoscale ablative material removal with subsequent chemical etching steps, ablation nanolithography and patterning of fused silica and crystalline silicon wafers has been demonstrated. Confinement of laser-induced crystallization to nanometric scales has also been shown. In-situ observation of the nanoscale materials modification was conducted by coupling the NSOM tips with transmission electron microscope (TEM) instrument. Nucleation and growth of semiconductor materials has been achieved by Laser Chemical Vapor Deposition (LCVD) at the nanoscale level. Optical properties of the grown nanowires have been examined by far-field and near-field laser induced fluorescence spectroscopy. Locally selective growth of crystalline silicon nanowires with controlled size heterogeneity and nanometric placement accuracy has been accomplished. Results on the fabrication of binary system semiconductor nanowires will be presented.
11:30 AM - FF8.5
Hierarchical Metallic and Ceramic Nanostructures Produced via a Hybrid Approach Combining Laser Interference Ablation and Block Co-Polymer Phase Separation.
Taiwo Alabi 1 , Dajun Yuan 2 , Suman Das 2
1 Material Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Mechanical Engineering, Georgia Institute of technology, Atlanta, Georgia, United States
Show AbstractOptical, electrical, thermal, magnetic and chemical properties of nano-scaled metallic and ceramic materials differ remarkably from their bulk counterparts. Harnessing such properties for device oriented fabrication has lead to numerous researches into nano-materials on surfaces. The placement and ordering of such nano-features on surfaces has been achieved using several techniques including soft lithography, dip-pen nanolithography, laser interference lithography (LIL), block copolymer phase separation, e-beam lithography, etc. Of all the above listed techniques for controlled placement of nano-features on surfaces, the two robust, inexpensive and high throughput techniques inarguably are the LIL technique and block co-polymer phase separation.Combining the two techniques and with block co-polymers acting as a positive tone photoresist, features having a secondary ordering given by the periodicity of the laser interference pattern and a primary ordering given by the inter-domain spacing of the phase separated block copolymers can be generated. The resulting feature density in a given periodic area can also be calculated and is shown to be considerably higher than is observed through LIL. By loading the block co-polymer with a metallic salt prior to laser interference patterning, and selectively removing the polymer via reactive ion etching, it is possible to generate metallic or ceramic nano-domains on the substrate with a superposition of the periodicity of both the block co-polymer phase and the LIL technique.We report here on the formation of hierarchical metallic and ceramic nanostructures using a novel hybrid technique combining laser interference microlithography and block co-polymer nanolithography. The hierarchical structures have a primary ordering domain periodicity of about 30-100nm corresponding with the primary ordering present in the sacrificial block co-polymer phase separating blocks, and a tunable secondary periodicity depending on the number of interfering laser beams, angle between the beams, and the intensity of the laser beam. The secondary periodicity ranges from 250 nm to 2 µm. By varying the loading time of the block co-polymer with metallic salts and the laser interference technique, different types of hierarchical structures can obtained. We demonstrate the ability to generate patterns having Au, Ag, Pt, Fe2O3, and PdO2 hierarchical nano-domains. Such a robust method could be applied to other metallic and ceramic materials and have possible use for large-scale production of nano-catalysts, photonics, optoelectronics and bio-sensors.
11:45 AM - FF8.6
Photothermal Laser Patterning of Buried Polymer Interfaces.
Anja Schroeter 1 2 , Steffen Franzka 1 2 , Nils Hartmann 1 2
1 Physical Chemistry, University of Duisburg-Essen, Essen Germany, 2 NanoEnergieTechnikZentrum, University of Duisburg-Essen, Duisburg Germany
Show AbstractCovalent attachment of polymer films provides a versatile means to taylor chemical and physical surface properties. Alternative to the approach of growing a polymer on a surface, here we report on a facile and flexible photothermal procedure for local grafting of thin polymer films to solid surfaces. Surface-oxidized silicon samples are coated with alkylsiloxane monolayers. After wet-chemical treatment in order to form azide-terminated monolayers a thin polymer film is spin-coated on top of the monolayer. Local irradiation with a focused beam of a diode-pumped solid-state laser at a wavelength of 532 nm thermally activates the azide groups at the buried polymer interface and leads to local covalent attachment of the polymer. Subsequently, polymer material, which is not coupled to the surface, is removed via sonication. The influence of incident laser power and irradiation time is investigated. At a 1/e focal spot diameter of 2.1 microns dots with diameters close to 1 micron can be fabricated. This procedure allows for rapid large-scale patterned attachment of a wide spectrum of polymers.
12:00 PM - FF8.7
Rapid Fabrication of Diverse Two-Dimensional and Three-Dimensional Gold Nanostructures through Laser Interference Patterning.
Dajun Yuan 1 , Suman Das 1
1 1.Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractGold nanostructures have been extensively studied. Several important discoveries have been revealed recently, such as large enhancement of nonlinear optical phenomena, surface-enhanced Raman scattering, and cell probe. A number of approaches have demonstrated successful fabrication of gold nanostructures, such as E-beam lithography, laser direct-writing, nanosphere lithography, and nanoimprint lithography. However, they are limited either by cost, low throughput or the ability to produce high aspect ratio nanostructures over large areas (>1 cm 2 ). Laser interference patterning makes use of the interference of two or more high-power pulsed laser beams, and involves just a single-step process. This technique allows the production of periodic structures with a well-defined long-range order in length scales ranging from a quarter of the wavelength to tens of micrometers, simply through the adjustment of the angles between interfering beams. The structuring process is based on photo-thermal, photo-physical or photo-chemical mechanisms, depending on the type of the material. Here, we report on the development of a simple, one-step method for the fabrication of diverse 2D and 3D nanostructures on gold films over areas spanning 1 cm 2 . Adhesion layers of titanium with 10 nm thickness and gold films of thickness from 10 nm to 500 nm are deposited by e-beam evaporation on silicon substrates. Laser interference patterning of these films with a 10 ns pulsed Nd:YAG emitting a wavelength of 355 nm wavelength at 10 Hz repetition rate creates periodic structures. Various periodic 2D nanostructures can be patterned on gold films of thickness less than 50 nm. For instance, grooves and gratings with feature sizes ranging from 100 nm to 2 µm can be created with two interfering beams, while hexagonal close-packed arrays of cavities and holes with feature sizes ranging from 100 nm to 2.5 µm can be created with three interfering beams. Various periodic 3D nanostructures can be created on gold films of thickness ranging from 50 nm to 500 nm. The variety of possible structures including nanodomes, nanomushrooms, and nanoneedles with feature sizes ranging from 10 nm to 2 µm can be created through careful adjustment of the laser intensity and the interference period. Characterization of the fabricated nanostructures through AFM and SEM reveals the probable mechanisms of their formation through pulsed laser induced melting and resolidification, in combination with surface tension driven effects. These novel structures have potential applications in field emission devices, surface-enhanced Raman spectroscopy, and cell probe examination.
12:15 PM - FF8.8
Nanofabrication with the Helium Ion Microscope.
Stuart Boden 1 , Zakaria Moktadir 1 , Hiroshi Mizuta 1 , Harvey Rutt 1 , Darren Bagnall 1
1 Electronics and Computer Science, University of Southampton, Southampton United Kingdom
Show AbstractThe emerging field of helium ion microscopy is rapidly establishing itself as a valuable surface imaging technique, capable of generating images exhibiting sub-nm resolution and a high depth of field, surpassing that possible with scanning electron microscopy (SEM) [1,2]. This is enabled by the atomically sharp helium ion source and the larger momentum (and so smaller de Broglie wavelength) of helium ions compared to electrons, which together result in a sub-nm probe focused on the sample and a small beam divergence angle. The focused beam of helium ions generated by the microscope can also be used for nanoscale modification of materials and so the helium ion microscope is being investigated as a novel nanofabrication tool in addition to a surface imaging instrument [3,4].Nanofabrication with the helium ion microscope is possible through direct ablation of surface material, analogous to the way a focused beam of gallium ions is used in focused ion beam (FIB) technologies. The controlled removal of material in this way can be used to mill intricate patterns into thin film and two dimensional materials, carving out nanoelectronic device designs with feature sizes smaller than can be achieved with Ga+ FIB. In addition, an integrated gas injection system allows deposition of metal from gaseous precursors in areas scanned by the beam [5].We will present our latest work on nanofabrication with the Zeiss Orion Plus helium ion microscope at Southampton. This includes the use of a dedicated pattern generator (XENOS XeDraw2) which can take control of the beam and scan it across the sample surface in defined patterns. The system also allows alignment between different write fields, opening up possibilities of all-in-one device and contact fabrication. We are using this to create single electron transistor and multiple quantum dot devices in graphene and other technologically important 2D materials.[1]B.W. Ward, J.A. Notte, and N.P. Economou, “Helium ion microscope : A new tool for nanoscale microscopy and metrology,” Journal of Vacuum Science and Technology B, vol. 24, 2006, pp. 2871-2874.[2]L. Scipioni, L.A. Stern, J. Notte, S. Sijbrandij, and B. Griffin, “Helium Ion Microscope,” Advanced Materials & Processes, vol. 166, 2008, pp. 27-30.[3]J. Yang, D.C. Ferranti, L. a Stern, C. a Sanford, J. Huang, Z. Ren, L.-C. Qin, and A.R. Hall, “Rapid and precise scanning helium ion microscope milling of solid-state nanopores for biomolecule detection.,” Nanotechnology, vol. 22, Jul. 2011, p. 285310.[4]D.C. Bell, M.C. Lemme, L. a Stern, J.R. Williams, and C.M. Marcus, “Precision cutting and patterning of graphene with helium ions.,” Nanotechnology, vol. 20, Nov. 2009, p. 455301.[5]S.A. Boden, Z. Moktadir, D.M. Bagnall, H. Mizuta, and H.N. Rutt, “Focused helium ion beam milling and deposition,” Microelectronic Engineering, (in press).
12:30 PM - FF8.9
Ion Irradiation, a New Tool to Shape Metallic Nanoparticles Embedded within an Host Matrix: Experiments and Simulations.
Abdallah Slablab 1 , Pierre-Eugène Coulon 1 , Giancarlo Rizza 1 , Sandrine Perruchas 2 , Thierry Gacoin 2 , Fabrice Gourbilleau 3 , Christian Dufour 3 , Julien Cardin 3
1 Laboratoire des solides irradiés, Ecole Polytechnique, Palaiseau France, 2 LPMC, Ecole Polytechnique, Palaiseau France, 3 CIMAP/CNRS, ENSICAEN, Caen France
Show AbstractAn innovative and powerful technique for manipulating matter at the nanometer scale by ion irradiation has been investigated since few years. This ion-shaping technique allows the deformation of metallic spherical particles embedded within an ion-deformable amorphous host matrix into prolate nanorods and nanowires. This creates new opportunities to obtain original noble-metal nanostructures that could not be produced by conventional lithography, chemical and etching techniques. Here, we show that this phenomenon is not limited to the transformation into prolate nanorods and/or nanowires, but that depending on the initial size of the NPs, several new classes of ion-shaped NPs can also be obtained: i) facetted-like NPs, ii) nanowires growing from a facetted core or iii) chromosome-like NPs. The objective of this work is a tentative to rationalize the ion-shaping process for all possible NP sizes. For this purpose, we introduce the concept of pressure solution creep, i.e. the stress-driven diffusion and re-precipitation of the metallic species through a liquid (premolten) NP surface layer. Finally, this model is checked by having recourse to a 3D implementation of the thermal spike model for anisotropic and composite media.
12:45 PM - FF8.10
Modeling, Design and Fabrication of a Freestanding Nanoporous Membrane.
Di Deng 1 , Denis Nothern 1 , David Liaw 3 , Thomas Liu 2 , Peter Peterson 2 , Brian Gilchrist 3 , Joanna Millunchick 1
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Electrical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 , ElectroDynamic Applications, Inc, Ann Arbor, Michigan, United States
Show Abstract Nanoporous membranes are widely researched on many application fronts. One challenge for nanoporous membrane research is to provide mechanically stable designs in spite of inherently weak strength from diminished dimensions. One such application is nanoparticle thruster, where chargeable nanoparticles are fed through a nanoporous membrane. Nanoparticles conglomerates are filtered and only one single nanoparticle is allowed to pass through the nanopore at a time. These functions therefore require stringent mechanical stability. In our work, we present a mathematical model that predicts the deflection behavior and strength of nanoporous membranes. Based on these prediction, as well as fabrication considerations, we propose a hierarchical design for a nanoporous membrane device for nanoparticle propulsion thruster application. Three layers in total, the hierarchical device bolsters a 200nm-thick nanomembrane patterned with 250nm nanopores on supporting structures. The hierarchical design is capable of funneling conducting nanoparticles to the nanoporous membrane and provide necessary strength, while making fabrication feasible. One such hierarchical nanoporous membrane device is fabricated with microfabrication techniques and focused ion beam lithography. A characterization with nano-indentation shows that the model accurately predicts the deflection behavior of the fabricated nanoporous membrane, which deflects proportionally to applied pressure without fracture up to 1MPa.