Benjamin Ocko Brookhaven National Laboratory
Jin Wang Argonne National Laboratory
Karl Ludwig Boston University
Thomas P. Russell University of Massachusetts
OO1: GISAXS Studies of Block Copolymer and Polymer Thin Films I
Tuesday PM, December 02, 2008
Room 104 (Hynes)
9:30 AM - **OO1.1
Probing the Self-Organization Kinetics in Block Copolymer Thin Films.
Detlef Smilgies 1 Show Abstract
1 CHESS, Cornell University, Ithaca, New York, United States
Thermal annealing and solvent annealing are two widespread techniques, in order to improve the degree of ordering in block copolymer thin films. In addition thermal and solvent treatment provide a unique view into polymer kinetics, if probed in-situ and in real time. Such studies can help to understand, why solvent annealing sometimes does not work and even may help to find windows of opportunity, how to make it work. Moreover, unique views of polymer phase stability and reversibility can be obtained. Thus in-situ GISAXS studies can provide a deeper insight into the intricate polymer self-organization processes under the influence of vapor pressure and temperature which may help to identify pathways to well ordered nanostructures.
10:00 AM - OO1.2
Long-Range Lateral Order in Block Copolymer Thin Film.
Soojin Park 1 , Russell Thomas 1 Show Abstract
1 Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts, United States
We demonstrate the fabrication of highly oriented line patterns that are in crystallographic registry with each other over whole substrates. This substrate has been used for guiding the self-assembly of block copolymers (BCPs) over very large area. In this study, the substrate having the sawtooth pattern presents a variation in the surface topography to any film that would be placed on the surface. Depending upon film thickness and width of groove patterns such as miscut silicon or sapphire, the orientation of cylindrical microdomains in polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and polystyrene-block-poly(ethylene oxide) (PS-b-PEO) BCP thin films can be controlled. Under certain conditions, perpendicular orientation of microdomains can be obtained over whole surface by thermal or solvent annealing. Cylindrical microdomains having long-range lateral order were investigated by scanning force microscope (SFM). To characterize the orientation of cylindrical microdomains and lateral ordering of PS-b-P4VP and PS-b-PEO BCP films over whole surface including substrates, grazing-incidence small angle x-ray scattering (GISAXS) experiments have been performed. Surface and internal structures of entire films have been evaluated at below and above the critical angle of polymer, respectively. And also GISAXS experiments have been carried out with rotation of sample stage to prove the orientational order of cylindrical microdomains.
10:15 AM - **OO1.3
GISAXS to Probe the Structure of Monolayer and Multilayer Films of Spherical-Domain Diblock Copolymer Blends with Homopolymer*.
Gila Stein 2 , Vindhya Mishra 2 , Edward Kramer 1 2 Show Abstract
2 Chemical Engineering, UCSB, Santa Barbara, California, United States, 1 Materials, UCSB, Santa Barbara, California, United States
10:45 AM - OO1.4
Enhanced Kinetics and Orientation Control in Self-Assembled Block Copolymer Films using Directed Thermal Gradients.
Ronald Jones 1 , Brian Berry 1 , Kevin Yager 1 , Alamgir Karim 1 , Sushil Satija 2 , Ho-cheol Kim 3 Show Abstract
1 Polymers Division, NIST, Gaithersburg, Maryland, United States, 2 NCNR, NIST, Gaithersburg, Maryland, United States, 3 , IBM Almaden Research Center, Almaden, California, United States
Self-assembly of block copolymer (BCP) films is considered a potential solution for patterning at the sub-20 nm scale for next generation electronics and ultra-high density magnetic data storage. A key challenge to the use of self-assembly in sub-20 nm patterning is the control of pattern placement on the scale of a single nanometer using processing techniques amenable to manufacturing. BCP domains are expected to rapidly form simple shapes such as posts or dense arrays of lines where the domain size is naturally of the sub-20 nm scale and all domains have uniform size, shape, and orientation. Among the many processing techniques available, a primary method of inducing self-assembly is through thermal annealing above the glass transition temperature of the block copolymer. Thermal fields have the advantage of being generally applicable to a wide range of polymer systems and would not introduce contaminants into fabrication facilities. However, thermal annealing suffers from the slow kinetics of assembly and defect annihilation required to achieve a defect-free pattern. We have investigated the use of non-uniform thermal fields as a route to enhancing control over both the orientation and kinetics of assembly in block copolymer films. Our results have demonstrated a surprising capability to direct the orientation of BCP phases while greatly enhancing the kinetics of assembly using directed thermal gradients. The structure of these films is probed non-destructively using a combination of Rotational Small Angle Neutron Scattering (SANS), Neutron Reflectivity (NR), and Grazing Incidence Small Angle X-ray Scattering (GISAXS). Using these techniques, we show the dependence of assembly kinetics on the magnitude and direction of a thermal gradient in a block copolymer film. We present results from a series of gradients of varying magnitude and direction relative to the substrate. The results demonstrate significantly increased control of ordering kinetics, with over an order of magnitude increase in the kinetics of ordering by varying the magnitude of the thermal gradient. In addition, the direction of the gradient is shown to play a key role in control of orientation and grain size. These effects are described using a simple field model. The effects describe are then synergistically combined with other methods used to process block copolymer films such as grapho-epitaxy, providing a potential route to further exploit a range of strategies previously explored by other groups.
11:30 AM - **OO1.5
Hierarchical Assemblies of BCP-Based Supramolecules in Thin Films.
Ting Xu 1 2 3 , Shih Huang Tung 1 Show Abstract
1 Materials Science and Engineering , University of California, Berkeley, Berkeley, California, United States, 2 Chemistry, University of California, Berkeley, Berkeley, California, United States, 3 Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
A key to future technologies is the design and fabrication of hierarchical materials having structures ordered down to the molecular level with built-in functionalities. Block copolymer (BCP)-based supramolecules can be constructed by associating small molecules to the side chain of one block, forming coil-comb shaped supramolecules. Upon phase separation, the small molecules provide rich chemical functionalities and molecular level assemblies and diblock copolymers may manipulate their assembly macroscopically as well as for easy processing.The hierarchical assemblies of supramolecules, consisted of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) with 3-pentadecylphenol (PDP) hydrogen-bonded to the 4VP, were investigated in thin films after solvent annealing in a chloroform atmosphere. The synergistic co-assembly of PS-b-P4VP and PDP was utilized to generate oriented hierarchical structures in thin films. Hierarchical assemblies, including lamellae-within-lamellae and cylinders-within-lamellae, were simultaneously ordered and oriented from a few to several tens of nanometers over macroscopic length scales. The lamellar and cylindrical microdomains, with a periodicity of ~ 40 nm, were oriented normal to the surface, while the assembly of comb-blocks, with a periodicity of ~ 4 nm, were oriented parallel to the surface. The macroscopic orientation of supramolecular assembly depends on the comb block fraction and can be tailored by varying PDP to 4VP ratio without interfering with the supramolecular morphologies. Furthermore, using one diblock copolymer, thin films with different hierarchical structures, i.e. lamellae-within-lamellae and cylinders-within-lamellae, were obtained by varying stoichiometry of PDP to P4VP. The concepts described in these studies should be general and applicable to other BCP-based supramolecular thin films, thus, creating an avenue to functional, hierarchically ordered thin films.
12:00 PM - **OO1.6
Quantitative Analysis of Buried Structures in Polymer, Nanoparticles and their Nanocomposites by GISAXS.
Zhang Jiang 1 , Michael Sprung 1 , Xuefa Li 1 , Suresh Narayanan 1 , Jin Wang 1 Show Abstract
1 X-ray Science Division, Argonne National Laboratory, Argonne, Illinois, United States
12:30 PM - OO1.7
Structure and Dynamics of Blockcopolymer Films.
Sanghoon Song 1 , Heeju Lee 2 , Wonsuk Cha 1 , Zhang Jiang 3 , Adrian Ruehm 4 , S. Sinha 5 , Hyunjung Kim 1 2 Show Abstract
1 Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul Korea (the Republic of), 2 Physics , Sogang University, Seoul Korea (the Republic of), 3 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States, 4 , Max Planck Institute for Metal Research, Stuttgart Germany, 5 Department of Physics, Univ. of California San Diego, La Jolla, California, United States
We have measured the structure and the dynamics of supported block copolymer films of poly(styrene)-b-poly(dimethylsiloxane) (PS-b-PDMS) in the melt using X-ray Photon Correlation Spectroscopy (XPCS) with grazing incidence scattering geometry. Block-copolymer films used in this study have an internal structure of spherical micelles. This ought to have a strong influence on the physical properties of the thin films. The experiments were performed at beamline 8-ID-I at the Advanced Photon Source (APS). Surface dynamics can, e.g., be measured as a function of film thickness and temperature and is related to the viscosity of the block copolymer. It is interesting to investigate the dynamics as a function of temperature since the glass transition of PDMS (-120°C) is remarkably lower than the glass transition of PS (100°C). We investigated the surface dynamics in the range of temperature between 170-210°C, much higher than the glass transition. In the process of analyzing the surface dynamics from XPCS results, we applied the theory of overdamped thermal capillary waves on thin films. They are also tested with bilayer model based on the surface layer enriched with PDMS measured by reflectivity and x-ray photoelectron spectroscopy. The surface tension obtained from static grazing incidence scattering data also shows that a PDMS layer segregates to the free surface of the film. By changing the incident angle, the surface dynamics and the micelle dynamics were selectively measured. The obtained viscosity will be compared with the value from the mechanical measurement of the bulk material. This work was supported by Korea Reasearch Foundation, Seoul Research and Business Development Program (10816), and Sogang University Research Grant (2007). Use of the Advanced Photon Source was supported by the US Department of Energy, Office of Science, Office of Basic Energy Science, under Contract No. DE-AC02-06CH11357.
12:45 PM - OO1.8
Thickness Induced Structural Changes in Polystyrene Films.
M. Mukhopadhyay 1 , Xuesong Jiao 2 , Laurence Lurio 3 , Zhang Jiang 1 2 , Jarrett Stark 3 , Michael Sprung 2 , Suresh Naryanan 2 , Alec Sandy 2 , Sunil Sinha 1 Show Abstract
1 Department of Physics, University of California San Diego, San Diego, California, United States, 2 Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois, United States, 3 Department of Physics, Northern Ilinois University, DeKalb, Illinois, United States
OO2: GISAXS Studies of Block Copolymer and Polymer Thin Films II
Tuesday PM, December 02, 2008
Room 104 (Hynes)
2:30 PM - **OO2.1
Resonant Soft X-ray Scattering and Resonant Gracing Incidence Scattering: Recent Developments and Prospects.
Harald Ade 1 Show Abstract
1 , NCSU, Raleigh, North Carolina, United States
During the last few years, Resonant Soft X-ray Scattering (RSoXS) [1-5] at photon energies near the carbon edge has greatly improved the selective and enhanced contrast afforded by Anomalous Small angle X-ray Scattering (ASAX) . The selective contrast achievable in RSoXS is moiety specific and reminiscent of the selective deuteration used for neutron scattering and reflectivity but does not require the expenses and efforts that deuteration entails. Additionally, RSoXS has high contrast and excellent scattering intensities even for very thin films, thus providing a good complement to Gracing Incident X-ray Scattering (GSAXS). This presentation will review the technical and methodological progress to date and showcase a number of applications. Emphasis will be placed on applications to organic electronic devices that use either multilayer structured or phase separated blend films. The potential of using RSoXS in a gracing incidence geometry and in particular to investigate buried interfaces will be discussed. 1.C. Wang, T. Araki and H. Ade, Appl. Phys. Lett. 87, 214109 (2005).2. T. Araki, et al., Appl. Phys. Lett. 89, 124106 (2006).3. C.F. Welch, et al., Polymeric Materials: Science & Engineering 93, 289 (2005).4. J.M. Virgili, Y.F. Tao, J.B. Kortright, N.P. Balsara and R.A. Segalman, Macromolecules 40, 2092-2099 (2007).5. G.E. Mitchell, et al., Applied Physics Letters 89, 044101 (2006).6. Y.S. Ding, S.R. Hubbard, K.O. Hodgson, R.A. Register and S.L. Cooper, Macromolecules 21, 1698-1703 (1988).
3:00 PM - **OO2.2
Grazing Incident Small Angle X-ray Scattering Studies on the Solvent Annealing Mechanism in PS-b-PEO Thin Films.
Russell Thomas 1 , Soojin Park 1 , Bokyung Kim 1 , Sung Woo Hong 1 , Sung Kwon Hong 1 Show Abstract
1 Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts, United States
Recently, polystyrene-block-poly(ethylene oxide) [PS-b-PEO] thin films have proven to be a good candidate as highly ordered and oriented templates or scaffolds for the fabrication of addressable storage device or incorporation of secondary materials such as bio-materials or metal salts. However, a significant drawback such as dewetting problem of the films during solvent annealing exists. To harness this dewetting problem, preswelling by water vapor is required before solvent annealing in benzene/water environment. When the films are exposed to benzene as a neutral solvent for both blocks and water as a selective solvent for PEO block, the films are covered with benzene molecules at first due to the higher vapor pressure, which results in the possibility of dewetting. Preswelling of PEO domain under water vapor can solve the dewetting problem. Results have shown that unusual coalescence of two PEO microdomains and reorientation of cylindrical microdomains were observed as a function of solvent annealing time. In the end, a significant enhanced lateral ordering of cylindrical microdominas oriented normal to the surface was observed. Contrary to immiscibility of benzene/water systems, one might expect miscible systems such as THF/water system, provides a significant difference of microdomain morphology. Our results have shown that solvent annealing in THF/water results in cylindrical microdomain reorientation from perpendicular to parallel. A significant enhanced lateral ordering of cylindrical microdominas oriented parallel to the surface was observed. Grazing-Incidence small angle x-ray scattering (GISAXS) experiments have been performed to understand the mechanism and dynamics of the microdomain reorientation and the location of PEO microdomains in thin films during solvent annealing. The GISAXS studies give tremendous insight into the effect of water preswelling in PS-b-PEO on the formation and ordering of the thin films.
3:30 PM - **OO2.3
3-Dimensional Control over Lamella Orientation and Order in Thick Block Copolymer Films.
Clemens Liedel 1 , Alexander Boker 1 2 , Larisa Tsarkova 1 , Violetta Olszowka 1 Show Abstract
1 Physikalische Chemie II, Universitat Bayreuth, Bayreuth Germany, 2 , Bayreuther Zentrum für Kolloide und Grenzflächen (BZKG), Bayreuth Germany
4:30 PM - **OO2.4
Near-Surface and Internal Lamellar Structure and Orientation in Thin Films of Rod-Coil Block Copolymers.
Rachel Segalman 1 2 , Bradley Olsen 1 , Xuefa Li 3 , Jin Wang 3 Show Abstract
1 Chemical Engineering, UC Berkeley, Berkeley, California, United States, 2 Materials Science Division, Lawrence Berkeley National Laboratories, Berkeley, California, United States, 3 Advanced Photon Source, Argonne National Laboratories, Argonne, Illinois, United States
5:00 PM - OO2.5
Fabrication of Functional Nanostructured Surfaces by the use of Blockcopolymer Self Assembly.
Andreas Froemsdorf 1 , Hamid Rahbar-Azad 1 , Norbert Franz 4 , Holger Stillrich 4 , Sabine Puetter 4 , Stephan Roth 2 , Till Metzger 3 , Geraldina Carbone 3 Show Abstract
1 , Institute of Physical Chemistry, Hamburg Germany, 4 , Institute of Applied Physics, Hamburg Germany, 2 , HASYLAB / DESY, Hamburg Germany, 3 , ESRF, Grenoble France
5:15 PM - OO2.6
In-Situ GISAXS Study on Surface Melting in Ultrathin Polyethylene Films.
Tadanori Koga 1 , Y. Wang 1 , M. Endoh 1 , J. Koo 1 , M. Rafailovich 1 , D. Schultz 2 , M. Lee 2 , X. Li 2 , J. Wang 2 Show Abstract
1 Mat. Sci & Eng., Stony Brook University, Stony Brook, New York, United States, 2 , APS, Argonne, Illinois, United States
The crystallization of ultrathin polymer films on solid substrates has been studied for decades due to its importance in determining interfacial properties of coatings. Numerous groups have demonstrated that the rate of crystallization, crystal orientation, and density of nucleation points can be very different from bulk. We previously observed that, by using the shear modulation force microscopy (SMFM) measurements, the surface melting temperature (Ts) of polyethylene (PE) thin films decreased by 40°C relative to the bulk melting temperature (Tm) when the thickness was close to the lamellar thickness formed in the film (~15 nm). Further, it was found that most lamellae took a nearly perpendicular orientation to the surface in the films more than 30 nm in thick, while the lamellae oriented flat-on with respect to the substrate below 15 nm thickness. In order to clarify the relationship between the depression in Ts and the surface structures, we characterized the melting behavior of the surface lamellar structures by using in-situ GISAXS. At the same time, we also utilized a grazing-incidence x-ray diffraction (GID) technique that allows us to monitor the change in the surface crystallinity. Based on these in-situ x-ray scattering results, we will discuss the mechanism of the surface melting in a confined geometry and the origin of the large suppression of the surface melting temperature observed by SMFM.
5:30 PM - **OO2.7
GISAXS Analysis in a Parallel Fashion.
Alexander Hexemer 1 , Chris Coleman-Smith 1 , Cheng Wang 1 , Eric Schaible 1 , Eliot Gann 1 , Howard Padmore 1 Show Abstract
1 Alexander Hexemer, LBNL, Berkeley, California, United States
OO3: Poster Session: GISAXS
Wednesday AM, December 03, 2008
Exhibition Hall D (Hynes)
9:00 PM - OO3.1
Characterization of Nano-Particulate and Nano-Porous Thin Films by GISAXS.
Jianhua Li 1 , Akhilesh Traparthi 1 , Lori Fields 1 , Adam Beitelman 1 , Thomas McNulty 1 Show Abstract
1 Materials Science, Rigaku Americas Corp, The Woodlands, Texas, United States
GISAXS has long been used as a quantitative technique for the characterization of ordered nanostructures prepared on top of appropriate substrates. In this presentation, we show some new applications of GISXAS in the characterization of random nano-particulate and nano-porous thin films which have attracted a great deal of interest in the past several years. We demonstrate, using metallic, dielectric, and polymer thin films as examples, the applicability of GISXAS in the determination the average particle / pore size, the particle / pore size distribution, and the inter-particle /pore correlations of the nano-particulate and nano-porous thin films.
9:00 PM - OO3.2
GISAXS Studies of the Ordering of Polystyrene-Polymethylmethacrylate Block Copolymers on Metal Substrates for Patterned and Aniostropy Graded Hard. Drive Media.
Vishal Warke 2 1 , Christopher Redden 2 1 , Martin Bakker 2 1 , Xuefa Li 3 , Dong Ryeol Lee 3 , Jin Wang 3 , Kunlun Hong 4 , Phillip Britt 4 , Jimmy Mays 4 Show Abstract
2 Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, Alabama, United States, 1 Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama, United States, 3 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States, 4 Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Bit patterned media, including media fabricated with a gradient in composition, is being developed as a potential path to higher information storage density. The formation of metal nanopillars with 20-30 nm repeat spacing and precisely controlled magnetic properties presents a significant challenge to current fabrication methods. We report on the development of cylinder forming block copolymer phases as a method to generate the desired patterns coupled with the processing steps necessary to transfer the pattern into magnetic material. GISAXS has been used to study the ordering of the block copolymer and the fidelity of pattern transfer during the various processing steps.
9:00 PM - OO3.3
Investigating Nanoscopic Patterned Surfaces Of a Semifluorinated Liquid Crystalline Diblock Copolymer Using X-Ray Scattering Techniques.
Mahmoud Al-Hussein 1 Show Abstract
1 Department of Physics, University of Jordan, Amman Jordan
Patterned surfaces on the nanoscopic length scale are desirable for many potential applications. A simple and rapid means for the fabrication of such surfaces is offered by self-assembling polymeric materials . In this context, diblock copolymers have been widely investigated [2,3]. They spontaneously self-assemble into nanometer-sized domains that exhibit well-ordered morphologies. These include spheres, cylinders, lamellae and bicontinuous structures, depending on the composition and the strength of the interblock interactions . Of particular interest, are diblock copolymers in which one of the two blocks is a side chain liquid crystalline polymer . In such a system, additional factors such as the elastic energy of the LC phase and the orientational wetting of the side chains at the interfaces contribute to the final morphology of the copolymer. Consequently, the interplay between the two self-assembling mechanisms can be exploited to generate functional nanoscopic structures with a hierarchical ordering [5-7].In this presentation I shall show that cylindrical domains with an average diameter of 20 nm normal to the surface can be obtained over very large area by merely spin-coating an asymmetric polymethyl methacrylate-fluorinated side chain liquid crystalline diblock copolymer onto a homogeneous substrate. The combination of smectic layering within the majority LC domains and orientational wettability of the side chains serves to stabilize the minority cylindrical domains normal to the substrate. A combination of techniques was used to investigate the surface morphology and the internal nanostructure of the thin films both perpendicular and parallel to the substrate. This includes atomic force microscopy (AFM), X-ray reflectivity (XR) and grazing-incidence X-ray scattering (GIXS) using synchrotron radiation.  Y. Xia, A. Rogers, K. E. Paul, G. Whitesides, Chem. Rev., 99, 1823 (1999). J. P. Spatz, S. Sheiko, M. Moeller, Adv. Mater., 8, 513 (1996). M. Park, C. K. Harrison, P. M. Chaikin, R. A. Register, D. H. Adamson, Science, 276, 1407 (1997). F. S. Bates, Science, 251, 898. (1991). W. H. de Jeu, Y. Serero, and M. Al-Hussein Adv. Polym. Sci.,71, 200 (2006). M. Al-Hussein, Y. Serero, O. Konovalov, A. Mourran, M. Moller, W. H. de Jeu, Macromolecules, 38, 9610 (2005). I. W. Hamley, V. Castelletto, Z. B. Lu, C. T. Imrie, T. Itoh, and M. Al-Hussein, Macromolecules, 37, 4798 (2004).
9:00 PM - OO3.4
In situ Observation of the Crystal Growth in Friction-Transferred poly(9,9-dioctylfluorene) Thin Films by Grazing Incidence x-ray Diffraction.
Masahiro Misaki 1 2 , Shuichi Nagamatsu 1 3 , Yuji Yoshida 1 , Nobutaka Tanigaki 1 , Kazuhiko Omote 4 , Kiyoshi Yase 1 , Yasukiyo Ueda 2 Show Abstract
1 , National Institute of Advanced Industrial Science and Technology, Tsukuba Japan, 2 , Kobe University, Kobe Japan, 3 , Kyushu Institute of Technology, Iizuka Japan, 4 , RIGAKU Corporation, Akishima Japan
Polyfluorene derivatives have been currently investigated for useful applications in highly polarized light-emitting diodes and high performance field effect transistors to control the molecular structure and alignment in thin films. By means of grazing incidence X-ray diffraction (GIXD), we confirmed the structure and alignment of poly(9,9-dioctylfluorene) (PFO) thin films prepared by friction-transfer methods which is one of molecular orientation techniques. It was revealed that the diffraction patterns strongly depended on an azimuthal angle, which is defined as the angle between the scattering vector and the friction direction in the film plane. In the parallel of scattering vector to friction direction, the 006 and 008 diffractions of PFO are observed. These reflections are not observed in the orthogonal to friction. This indicates that the polymer backbone (main chain) is aligned parallel to the friction direction. The half-width of the orientational distribution of 008 diffraction was determined to be approximately 11.0 degree. Further, we found the phenomena which the friction-transferred PFO re-arranged by slow crystallization from nematic liquid crystal phase. After re-arrangement of PFO, the half-width of the distribution of 008 diffraction was intensively improved to 1.6 degree.In this study, we have mainly investigated the mechanism of molecular rearrangement during the crystal growth by using in-situ GIXD set with a temperature control unit. In order to observe the crystal growth rate from liquid crystal, we have performed time-dependent measurement of diffraction intensities during isothermal re-crystallization process at various constant temperatures. As a result, the time constant of 008 diffraction on crystal growth at 413 K was twice the time constant of 040 diffraction. We confirmed the crystal growth rate along the b-axis was faster than that along c-axis.
9:00 PM - OO3.5
Solvent-vapor Annealing of Thin Films of PS-b-PEO Diblock Copolymers.
Sung Woo Hong 1 , Bokyung Kim 1 , Sookin Park 1 , Sung Kwon Hong 2 , Ji Xu 1 , Thomas Russell 1 Show Abstract
1 Polymer Science and Engineering, UMass Amherst, Amherst, Massachusetts, United States, 2 Dept. of Polymer Science & Engineering, Chungnam National University, Daejon Korea (the Republic of)
A two step solvent exposure process has been used to anneal thin film of PS-b-PEO block copolymer (BCP) involving a pre-swelling of the as-spun film with water vapor followed by solvent annealing of this thin film under a mixed organic solvent/water vapor atmosphere. When the pre-swollen film is exposed to benzene and water vapor, cylindrical PEO microdomains are oriented normal to the surface. However, with increasing solvent annealing time, an unusual coalescence of only two cylindrical PEO domains is observed, which results in a rod-like microdomain structure over the entire film. With further solvent annealing, the rod-like PEO microdomains are transformed to larger cylindrical PEO microdomains oriented normal to the surface. The resulting film shows significantly enhanced lateral ordering of larger cylindrical PEO microdomains without dewetting. Depending on pre-swelling time, the domain size and interdomain spacing of the cylindrical PEO microdomains can be controlled. The larger domain size and domain spacing are obtained when pre-swelling time is short, while the smaller size and spacing are obtained with longer pre-swelling times. When THF and water are used for solvent annealing instead of benzene and water, PS-b-PEO BCP thin films exhibit a different morphological transition. At the initial stage of solvent annealing, cylindrical PEO microdomains oriented normal to the surface are observed, similar to that seen with benzene/water exposure. However, as the solvent annealing time increases, cylindrical PEO microdomains merge, resulting in cylindrical microdomains oriented parallel to the surface with long-range lateral ordering. Scanning force microscopy and grazing incident small angle x-ray scattering have been performed to investigate and understand the mechanisms of the morphological transitions of PEO microdomains during solvent annealing.
9:00 PM - OO3.6
Investigation of Structural Characteristics of Nanorods by Reciprocal Space Mapping in Grazing Incidence Geometry.
Sanghwa Lee 1 , Yuri Sohn 1 , Chinkyo Kim 1 , Dong Ryeol Lee 2 Show Abstract
1 Physics, Kyunghee University, Seoul Korea (the Republic of), 2 Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Nanostructured materials have unique physical, chemical and catalytic properties which are not observed in thin films or bulk state. These interesting properties of nanostructures have attracted a lot of attention for their possible application to nanodevices. In particular, vertically aligned nanostructures on a substrate are promising candidates for fabrication of optoelectronic nanodevices. Vertically aligned nanostructures can be grown either by catalyst-assisted or by catalyst-free method, but it is generally believed that the catalyt-assisted growth has advantage over catalyst-free method in controlling position, density and diameter of nanorods. Thus, the catalyst-free growth has been less extensibly studied than the catalyst-assited growth. In particular, the research on the preferred growth directions of nanorods grown by catalyst-free method is very rare. In this work, a horizontal HVPE system was used for preparing GaN nanorods and their preferred growth direction characteristics were investigated by a new approach, synchrotron x-ray reciprocal space mapping (XRSM) in grazing incidence geometry. Interestingly most of GaN nanorods were grown along c-direction, but more than one preferred growth directions were found. XRSM method clearly revealed the relative orientations of these preferred growth directions. Details on this method in conjunction with the obtained results will be discussed. This work was supported in part by the Seoul Research and Business Development Program-Grant No.10583.
9:00 PM - OO3.7
Self-assembly of Well-ordered, Close-packed 2D Arrays of Recombinant Virus-like Particles that Nucleate the Growth of Inorganic Nanomaterials.
Carlee Ashley 1 , Darren Dunphy 1 , Eric Carnes 1 , Dimiter Petsev 1 , Plamen Atanassov 1 , David Peabody 2 , C. Jeffrey Brinker 1 3 Show Abstract
1 Chemical Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 2 Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico, United States, 3 Self-Assembled Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States
Due to their high degree of monodispersity, their highly symmetrical geometries, and the ease with which their protein capsids can be genetically engineered, bacteriophages are well-suited for use as templates in the spatially-defined self-assembly of inorganic materials into highly-ordered nanostructures. To this end, we used an evaporation-driven deposition technique, convective assembly, to self-assemble 28-nm icosahedral bacteriophages, MS2 and Qβ, into well-ordered hexagonal close-packed (hcp) monolayers, the long-range order of which was confirmed via Grazing Incidence Small-Angle X-ray Scattering (GISAXS) characterization at a synchrotron source. Convective assembly enables rapid deposition of colloidal particles onto a hydrophilic surface by trapping microliter-sized droplets between two fixed-angle plates and dragging the ensuing meniscus across a surface with constant velocity. We utilized in-situ GISAXS to monitor the time-dependent development of bacteriophage nanostructures and to determine the affect of particle-particle and particle-substrate interactions on long-range order. We patterned surfaces with alternating hydrophobic and hydrophilic regions; phage particles selectively wet hydrophilic regions, enabling us to construct patternable devices with nanometer-sized features. We then engineered virus-like particles (VLPs) of MS2 to express, at specific surface locations, non-native peptides that have been demonstrated to nucleate the growth of gold from an aqueous salt solution. We have characterized the affinity of VLPs displaying the gold-binding peptide in relation to wild-type VLPs and to VLPs displaying 90 cysteine residues using SDS-PAGE and electron microscopy. Prior to reaction with the gold salt solution, we stabilized the VLP monolayers using either covalent attachment to a surface or immobilization in silica. To covalently link VLPs to a surface, we employed self-assembled monolayers capable of bonding with primary amine or carboxylic acid-containing amino acid residues in the VLP capsid. To stabilize VLP monolayers within nanostructured silica, we have used traditional and biomimetic approaches. We first immobilized VLPs via evaporation-induced self-assembly of an acidified sol containing a pre-hydrolyzed silica precursor dissolved in a volatile solvent, but we found that the harsh conditions associated with traditional sol-gel techniques disrupted the three-dimensional structure of the VLP capsid. Therefore, we have created mosaic VLPs that display both the gold-binding peptide and the R5 peptide, which is found in proteins isolated from diatoms and catalyzes silica condensation under neutral pH, biocompatible conditions. We are currently working on selectively condensing silica on the surfaces of hcp VLP structures while nucleating the growth of gold nanoparticles within VLP capsids in order to create “nano-capacitors” and other devices with unique electrical and optical properties.
9:00 PM - OO3.8
Nanoscale Ge Islands on Faceted Si(113) Studied by Grazing-Incidence Small-Angle X-Ray Scattering.
Thomas Schmidt 1 , Moritz Speckmann 1 , Radowan Hildebrand 1 , Sigrid Bernstorff 2 , Jens Falta 1 Show Abstract
1 Institute of Solid State Physics, University of Bremen, Bremen Germany, 2 , Sincrotrone Trieste, Basovizza Italy
Ge quantum dots are of high interest for application in Si based electronic and optoelectronic devices. Fabrication via self-assembly, though most promising in terms of scalability and mass production, generally does not offer a precise control of the size distribution of the quantum dots, the homogeneity of which, however, plays an important role for technological applications. As we have already shown earlier [1, 2], submonolayer adsorption of Ga on Si(111) can lead to an improved spatial dot-dot correlation and size distribution. An even more pronounced influence of Ga pre-adsorption is found on Si(113). Upon Ga saturation of the Si(113) surface, a well-ordered array of facets with alternating (112) and (115) orientation is found . For subsequent Ge growth, the formation of small Ge islands aligned at these facets has been observed . In the present study, the morphology of such Ge islands is investigated by grazing-incidence small-angle x-ray scattering (GISAXS).Samples were prepared by molecular beam epitaxy. Ga was deposited on clean Si(113) at 550°C until saturation was achieved and the surface was completely faceted, as monitored by in-situ high-resolution low-energy electron diffraction. Then, Ge was grown at a substrate temperature of 450°C. Owing to surface oxidation at ambient conditions, no clear indication of a regular substrate facet arrangement is observed with GISAXS. However, inclined streaks are found in the data. Contradicting Friedel's rule, these streaks do not appear symmetrically and therefore cannot be attributed to a two-dimensional spatial correlation. Instead, they are well explained in terms of crystal truncation rods (CTRs) emerging from the side facets of the Ge islands. This is also confirmed by the dependence on the azimuthal orientation with respect to the incoming beam. If the beam impinges along the [–1,1,0] crystal orientation, streaks are found for q∥ < 0 only, whereas the streaks appear exclusively at q∥ > 0 when the sample is rotated by 180°. No streaks are observed for the incoming beam along [3,3,–2]. From the observed inclination angle of 30° and from the azimuthal orientation, the corresponding facets are identified as (111) facets. Moreover, the average facet width has been quantified by GISAXS to be typically 100 nm. All the GISAXS results are in good agreement with complementary scanning electron micrographs (SEM). Th. Schmidt, S. Gangopadhyay, J. I. Flege, T. Clausen, A. Locatelli, S. Heun, and J. Falta, New J. Phys. 7, (2005) 193. Th. Schmidt, J.I. Flege, S. Gangopadhyay, T. Clausen, A. Locatelli, S. Heun, and J. Falta, Phys. Rev. Lett. 98 (2007) 066104. T. Clausen, Th. Schmidt, J. I. Flege, J. Falta, A. Locatelli, T. O. Mentes, S. Heun, and F. Z. Guo, e-J. Surf. Sci. Nanotech. 3 (2005) 379. Th. Schmidt, T. Clausen, J. I. Flege, S. Gangopadhyay, A. Locatelli, T. O. Mentes, F. Z. Guo, S. Heun, and J. Falta, New J. Phys. 9 (2007) 392.
9:00 PM - OO3.9
GISAXS Study of Porous SiOCH Dielectrics used in Advanced Microelectronic Interconnections.
J. Simon 1 , V. Jousseaume 2 , A. Zenasni 2 , D. Babonneau 3 Show Abstract
1 Science et Ingienerie des Materiaux et Procedes, INP-UJF-CNRS , Saint Martin d'Heres France, 2 , CEA-LETI-MINATEC, Grenoble France, 3 PHYMAT, Universite de Poitiers, Futuroscope France
Benjamin Ocko Brookhaven National Laboratory
Jin Wang Argonne National Laboratory
Karl Ludwig Boston University
Thomas P. Russell University of Massachusetts
OO4: GISAXS Studies of Nanoparticle and Nanoporous Thin Films
Wednesday AM, December 03, 2008
Room 104 (Hynes)
9:30 AM - **OO4.1
Looking by GISAXS at Growth and Catalytic Reaction of Oxide Supported Metal Nanoparticles.
Remi Lazzari 1 , Miguel Mantilla 1 , Jacques Jupille 1 , Marie-Claire Saint-Lager 2 , Pierre Dolle 2 , Gilles Renaud 3 , Odile Robach 3 , Frederic Leroy 4 Show Abstract
1 , Institut des NanoSciences de Paris, Paris France, 2 , Institut Néel, Grenoble France, 3 , CEA-Grenoble, Institut NanoSciences et Cryogénie, Grenoble France, 4 , Centre Interdisciplinaire de Nanoscience de Marseille , Marseille France
X-ray scattering techniques using the grazing incidence geometry offer the opportunity to probe in situ the crystallographic structure and the morphology of metal nanoparticles grown on oxide planar surfaces. Combining wide angle (GIXD) and small angle scattering (GISAXS) can give some insights into connected thermodynamic and kinetic parameters of metal/support interface, namely the role of stress due the lattice mismatch on the epitaxial orientation, the adhesion/wetting properties, the particle equilibrium shape and the peculiarities of the growth modes and the chemical reactivity. One key advantage of X-ray is the capability to perform measurement not only during particle growth under vacuum conditions but also at high pressure during the course of an actual catalytic reaction. This will be illustrated with our recent results on Au/TiO2(110), a model planar system of gold-based catalyst. Among others, the following points will be discussed:(i) The theoretical development made to analyse quantitatively the GISAXS patterns beyond the classical approximations, in particular to account for the profile of refraction index and the particle-particle correlations.(ii) The self similarity during the dynamic coalescence of Au/TiO2(110), on the size distribution but also on the spatial ordering of the particles and its link with the randomness of the nucleation centers.(iii) The sintering of nanoparticles during the course of the CO oxidation reaction and the link between particle size and chemical reactivity measured by mass spectrometry.
10:00 AM - OO4.2
In-situ Characterization of Nanoparticle Assembly using Grazing-Incidence Small-Angle X-Ray Scattering.
Darren Dunphy 1 , Hongyou Fan 2 , Shisheng Xiong 1 , Steven Gaik 3 , Hugh Hillhouse 3 , Michael Sprung 4 , Zhang Jiang 4 , Jin Wang 4 , C. Jeffrey Brinker 1 2 Show Abstract
1 , University of New Mexico, Albuquerque, New Mexico, United States, 2 , Sandia National Labs, Albuquerque, New Mexico, United States, 3 , Purdue University, West Lafayette, Indiana, United States, 4 Advanced Photon Source, Argonne National Labs, Argonne, Illinois, United States
Nanoparticle films with well-ordered 2D (monolayer) or 3D lattice arrays, formed through a rapid self-assembly process, often exhibit new or improved functional properties relative to non-structured materials. Selection of the nanoparticle lattice type, as well as optimization of long-range order, requires a fundamental understanding of the self-assembly pathway, necessitating the use of characterization tools capable of real-time analysis of transient nanostructures under ambient conditions. Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) at a synchrotron facility easily meets these criteria; we describe here our on-going efforts directed at using GISAXS at the Advanced Photon Source to follow the in-situ assembly of nanoparticle films. We have investigated the formation of both 2D and 3D arrays of Au nanocrystals from cast droplets as well as films deposited using a horizontal coating technique. For 3D arrays, we have encapsulated Au NCs within surfactant micelles, forming water-stable NCs that assemble into either a face-centered or body-centered cubic lattice in a process consistent with that of colloidal assembly of charged particles modulated by electrostatic screening. Recently, we have also begun studies of 2D Au NC assembly within thin (ca. 50 nm) polymer membranes cast upon water surfaces, investigating the long-range structure of the 2D array in addition to the position of the NC layer within the polymer film thickness as a function of processing conditions. An important component of our studies is the simulation of scattering data for both 2D and 3D systems; we will present simulated GISAXS data to demonstrate how these efforts add to our physical understanding of the self-assembly process.
10:15 AM - **OO4.3
Grazing-Incidence Small-Angle X-ray Scattering Studies in Size Selected Catalysts.
Randall Winans 1 , Byeongdu Lee 1 , Soenke Seifert 1 , Stefan Vajda 2 , Sungsik Lee 2 Show Abstract
1 X-ray Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Chemical and Engineering Science, Argonne National Laboratory, Argonne, Illinois, United States
In the study of catalytic reactions, grazing incidence SAXS (GISAXS) experiments on flat catalytic support substrates with size-selected metal clusters can provide both ex-situ and in-situ information on cluster size, shape, and inter-particle distance (APS beamline 12-ID). GISAXS can also give depth profile information, and the aspect ratio (height/diameter) of a cluster can be calculated from the GISAXS data to obtain the interfacial energy. GISAXS is ideal for in-situ studies since it is very sensitive to surface species and there is less parasitic scattering resulting from the substrate compared to a conventional direct-transmission SAXS experiment. GISAXS has been used to study the thermal stability and reactivity of Pt, Au, and Ag clusters (6 – 12 atoms) deposited on a variety of surfaces with insightful results(1). One example is the partial oxidation of olefins to alkyl oxides where it has been found that the size and shape of catalytic size-selected nanoparticles is important. ASAXS refers to the extension of standard SAXS experiments in which the energy of the probing X-rays is tuned near the absorption edge of an element in the sample. This method overcomes the problem of separating the scattering of clusters from that of the support. For the first time anomalous GISAXS has been obtained on metal clusters on surfaces and has provided significant insight into the structure of very small metal clusters on surfaces(2).Work performed at Argonne and use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. References:1.Winans, R. E.; Vajda, S.; Ballentine, G. E.; Elam, J. W.; Lee, B.; Pellin, M. J.; Seifert, S.; Tikhonov, G. Y.; Tomczyk, N. A. Topics in Catalysis 2006, 39, 145-149.2.Lee, B.; Seifert, S.; Riley, S. J.; Tikhonov, G.; Tomczyk, N. A.; Vajda, S.; Winans, R. E. Journal of Chemical Physics 2005, 123, 074701/1-074701/7.
10:45 AM - OO4.4
Structural and Chemical Properties of Self-Assembled Close-Packed Nanoparticle Films under Harsh Conditions.
Jan Flege 1 , Bernhard Gehl 2 , Thomas Schmidt 1 , Vesna Aleksandrovic 3 , Andreas Froemsdorf 3 , Andreas Kornowski 3 , Angelika Pretorius 1 , Sigrid Bernstorff 4 , Andreas Rosenauer 1 , Horst Weller 3 , Marcus Bäumer 2 , Jens Falta 1 Show Abstract
1 Institute of Solid State Physics, University of Bremen, Bremen Germany, 2 Institute of Applied and Physical Chemistry, University of Bremen, Bremen Germany, 3 Institute of Physical Chemistry, University of Hamburg, Hamburg Germany, 4 , Sincrotrone Elettra, Trieste Italy
11:30 AM - OO4.5
Modifying the Pore Size of Resorcinol Formaldehyde Aerogels for Fabrication of Hollow Spheres for Direct Drive ICF Experiments.*
Reny Paguio 1 , Chris Frederick 1 , Jared Hund 1 , Abbas Nikroo 1 , Mary Thi 1 Show Abstract
1 , General Atomics, San Diego, California, United States
Resorcinol Formaldehyde (R/F) aerogel has been used in the fabrication of hollow spherical targets for direct drive Inertial Confinement Fusion (ICF) experiments at the University of Rochester Laboratory for Laser Energetics (LLE). Recent cryogenic experiments at LLE using R/F shells have shown advantages of larger pore foam compared to the standard R/F formulation with pores of <100 nm. Previous work on modifying the pore size of the R/F aerogel was done by decreasing the base catalyst to resorcinol ratio, creating a large pore R/F aerogel (~ >0.5 um) through reaction limited aggregation. With modifications to this process we were able to successfully fabricate and characterize larger pore R/F aerogel shells for these experiments. A drawback to this process is that the density of the aerogel is lower than expected. The density reduction is due to less catalyst in the base catalysis part of this two-step polycondensation reaction, which forms less hydroxymethyl adducts in the reaction. This work investigates an alternative way to modify the pore size of the R/F aerogel without any significant change to the aerogel target density. This was successfully accomplished by an addition of hydrophilic polymer additive [Poly Vinyl Alcohol (PVA) or Poly Acrylic Acid (PAA)] to the R/F precursor solution which acts as an impurity in the reaction. The polymer can modify the cross linking of the hydroxymethyl adducts which can change the formation of the aerogel, thus changing the pore size. This modification successfully increases the pore size of the R/F aerogel with little or no change to the precursor’s gelation time which made it possible to use the same fabrication process used for standard pore size R/F aerogel spheres. This paper will discuss the process modifications and the fabrication of hollow, large pore R/F aerogel spheres. The resulting aerogels were characterized for pore size distribution with electron microscopy, nitrogen gas adsorption, visible spectroscopy, and small angle x-ray scattering. *Work supported by General Atomics IR&D funds.
11:45 AM - OO4.6
GISAXS Studies of Substrate Dependent Periodicity of SBA-15 Mesoporous Silica Thin Films.
Martin Bakker 1 2 , Roger Campbell 1 , Jason Manning 1 2 , Dong Ryeol Lee 3 , Xuefa Li 3 , Jin Wang 3 Show Abstract
1 Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama, United States, 2 Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, Alabama, United States, 3 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States
Mesoporous silica thin films are of wide interest as separations media, catalyst support, and hard templates, among many other potential applications. Very little work has been reported on the formation of such films on metal substrates. This in part may be due to the limited adhesion of such films on gold and platinum. SBA-15, a block co-polymer templated mesoporous silica phase consisting of hexagonally ordered arrays of pore, is found to adhere to a wide range of metals, even after removal of the block copolymer template. GISAXS analysis based on a Hexagonally Perforated Lattice (HPL) gives good agreement with the positions of the observed GISAXS intensity. The periodicity of the mesostructure in the films is found to vary reproducibly with metal. Removal of the polymer template causes a shrinkage of the films perpendicular to the substrate surface. Electrodeposition of nickel into the films reverses this shrinkage. The periodicity, and extent of the shrinkage are found to correlate with reduction potential of the metal. This may reflect the effect of metal dissolution during setting of the mesoporous silica films.
12:00 PM - OO4.7
In-situ Study of the Formation of Mesoporous Phases within the Pores of Anodic Alumina Membranes.
Ralf Koehn 1 , Barbara Platschek 1 , Markus Doeblinger 1 , Thomas Bein 1 Show Abstract
1 Chemistry & Biochemistry, University of Munich (LMU), Munich, Bavaria, Germany
The preparation of oriented mesoporous thin films by evaporation-induced self-assembly (EISA) has been well established in the past few years [1,2]. On the other hand, anodic alumina membranes (AAMs) with well-aligned channels normal to the membrane surface with pore sizes ranging from several dozen to hundreds of nanometers attracted considerable attention as templates for the growth of a variety of nanostructures [3,4]. A combination of both approaches, using the AAMs as hosts for the growth of the mesoporous material, leads to the formation of hierarchical structures consisting of a hexagonal silica mesophase within the ordered pores of the AAMs. Using ionic cetyltrimethylammonium bromide (CTAB), non-ionic decaethylene glycol hexadecyl ether (Brij56) or triblock-copolymer Pluronic 123 as templating agents, 2D-hexagonal mesostructures with two different orientations were obtained . In one case the mesopores are aligned parallel along the AAM-channels (columnar orientation), in the other case the mesopores show a circular orientation perpendicular to the AAM-channels. Both coexist at various ratios, depending on the composition of the precursor mixtures as well as synthesis conditions, e.g. the humidity during the evaporation process. This behaviour illustrates the high sensitivity and flexibility of the system. Aiming at a greater control over the synthesis, the mechanism of the formation of the mesoporous material inside the confined environment of the AAM-channels was investigated by in-situ grazing incidence small-angle X-ray scattering (GISAXS) experiments at the 1-BM beamline at the APS at ANL, Argonne, IL, USA [6,7]. The incident beam is almost parallel to the planar AAM-membrane surface, which is perpendicular to  in case of the columnar orientation, and perpendicular to the stacking axes of the tori in case of the circular orientation. This is the reason why in case of the columnar orientation, two reflexes in the horizontal plane of the primary beam will appear, while in case of the circular orientation four additional out of plane reflexes occur. Various structural transitions were observed, for the mesophase inside the AAM-channels as well as for the film that was formed on the planar membrane surface. It was possible to link humidity and weight loss during the EISA process to the transformation and formation of structures for the first time.C.J. Brinker, Y. Lu, A. Sellinger, H. Fan, Adv. Mater. 11, 1999, 579. D. Grosso, F. Babonneau, P.-A. Albouy, H. Amenitsch, A. R. Balkenende, A. Brunet-Bruneau, J. Rivory, Chem.Mater. 14, 2002, 931. C. R. Martin, Science 266, 1994, 1961. T. E. Mallouk, Science 291, 2001, 443. B. Platschek, N. Petkov, T. Bein, Angew. Chem. Int. Ed. 45, 2006, 1134. B. Platschek, R. Koehn, M. Doeblinger, T. Bein, Langmuir 24, 2008, 5018. B. Platschek, R. Koehn, M. Doeblinger, T. Bein, ChemPhysChem 2008, in press.
12:15 PM - OO4.8
The Effect of Heating Rate on the Porogen Behavior and Pore Sizes in the Methylsilsesquioxane/Porogen 2-Phase Low-k Films.
Yu-Hen Chen 1 , Jihperng Leu 1 Show Abstract
1 Department of Materials Science and Engineering, National Chiao-Tung University, Hsichu Taiwan
As devices scaling continues towards 32 nm node and beyond, further reduction of RC delay in the backend interconnects necessitates the development of ultra low-dielectric (k<2.5). In order to achieve k<2.5 while maintaining fairly good mechanical strength, incorporation of pores into dielectric materials using sacrificial porogen has been proved to be one of the viable methods. Recently, a late-porogen-removal scheme was proposed to form porous dielectrics by decomposing the porogen at T>350C after the completion of a metallization layer, in order to circumvent the reliability issues encountered in the integration of as-deposited porous dielectric. However, prior to thermal decomposition, the porogen stays in the dielectric matrix during various backend processing temperature cycling, making the control of porogen size difficult due to the potential aggregation of porogens and its interaction with matrix. Moreover, it is highly desirable to reduce pore size to increase mechanical strength, while increase the porosity to reduce the dielectric constant of porous dielectric. In this study, the effect of heating rate on the high-temperature porogen behavior in the matrix and final pore size/distribution was investigated. In particular, a spin-on organosilicate, methylsilsesquioxane (MSQ) and tri-block polymer, polystyrene-b-polybutadiene-b-polystyrene (SBS) were used as matrix and high temperature porogen (Td~400C), respectively. They were mixed in THF and spun on silicon wafer, then cured to 200C to form 2-phase MSQ/SBS films. A slow heating rate of 2C/min and an ultra-fast heating rate by curing the film on a hot-plate pre-heated at 200C were employed for comparison. FTIR spectroscopy was used to monitor the degree of cross-link in MSQ through the cage/network Si-O ratio, while rheometer was employed to monitor the viscosity of the 2-phase films as a function of cure temperature. Furthermore, in-situ grazing incidence small-angle X-ray scattering analysis(2-D GISAXS)of MSQ/SBS films was carried out to study the evolution of porogen during the curing process.The viscosity of 2-phase films cured at slow heating rate decreased as curing temperature exceeded 150oC, then increased at T>200C. In contrast, the viscosity of 2-phase films cured at a fast heating rate was much higher, indicating that fast curing induced MSQ matrix cross-link rapidly and the cross-linked matrix inhibited the porogen diffusion. In-situ 2-D GISAXS analysis of MSQ/SBS films showed the SBS porogen aggregated in the 2-phase films with increasing temperature and the porogen sizes were 11.3 nm for slow heating rate and 4.7 nm for fast heating rate condition. Moreover, the pore size and distribution of MSQ/SBS films based on BET and SEM studies could be modulated from 7-72 nm to 1-4 nm by increasing the heating rate. In summary, fast curing of 2-phase MSQ/SBS films enabled the formation of small pore sizes and distribution in the porous low-k based on late-porogen removal scheme.
12:30 PM - OO4.9
Round and Square Pore Formation in Nanoporous Anodized Aluminum Oxide.
Hau Wang 1 , Catherine Han 2 , Byeongdu Lee 3 Show Abstract
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 , R.J. Daley College, Chicago, Illinois, United States, 3 X-Ray Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Pattern formation through self-assembly during etching in inorganic material system is fairly uncommon. Nanopore formation in Al, Ti, and some compound semiconductors such as GaAs, InP, etc. are some of the examples. We have focused on aluminum anodization to form nanoporous alumina because the resulting patterns are highly controllable, the materials are stable, non-toxic, and the porous alumina can be used as templates for nanowire and nanotube preparation. The anodization process typically started with electro-polishing followed with oxidation of the metal thin foil under an applied electrical field in an etching solution. Round shaped nanopores with diameters ranging between 20 to ~200 nm arranged in a hexagonally close packed pattern are typically observed. The pore diameters, pore-to-pore distance can be controlled through the anodization potential. We studied the early stage of pore formation with small angle x-ray scattering (SAXS) and grazing incident (GISAXS) techniques (MRS Proc. Vol. 951 0951-E09-10). The pore height increased as a function of the square root of anodization time. In addition, we applied anodization at 40V to generate a set of nanoindents on the aluminum surface. These nanoindents were used to create a set of lattice with lattice constant reduced from a to a/sqrt(3). When aluminum surface was scratched or imprinted with micrometer wide line patterns, upon anodization, square pores roughly equal-spaced along the line were observed unexpectedly. Double lines, triple lines, and twined double lines were observed. The double lines consist of two linear arrays of square pores, while the triple lines consist of a third linear array of round pores in the middle. The inner sides of the square pores in the triple lines tend to be somewhat rounded. Interactions between these square and round pores are clearly evident. Twined double lines are two double lines with a slightly larger gap between the two sets of lines. The square pore formation may be understood from our SAXS and GISAXS in-situ studies. The distances between initial nucleation sites tend to be small. When these initial sites are trapped in a line defect, they can not freely move around. Upon anodization, the mechanical stress between neighboring pores leads to the square pore formation. These results will be presented.Work at MSD and APS Argonne National Laboratory as well as FESEM carried out at EMC are supported by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.
12:45 PM - OO4.10
In Situ Structural Characterization of Porous SnOx Nanostructures Using GISAXS.
Tao Sun 1 2 3 , Suresh Donthu 1 2 , Michael Sprung 3 , Zhang Jiang 3 , Jin Wang 3 , Vinayak Dravid 1 2 Show Abstract
1 Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States, 2 International Institute for Nanotechnology, Northwestern University, Evasnton, Illinois, United States, 3 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States
SnOx is the most commonly used semiconducting oxide gas sensor for variety of applications such as monitoring domestic air quality and hazardous exhaust gases at many work sites. Doping SnOx with Pd can highly enhance its gas sensing performance. Two mechanisms are proposed and frequently applied to explain the influence of the Pd doping, which are electronic and chemical sensitizations. Besides them, doping also changes the microstructure of the films. It has been widely demonstrated that the grain size and pore size significantly determine sensing properties. However, the structural information has rarely been quantified due to paucity of in situ characterization techniques, particularly for pores. Therefore, in order to fully understanding the effects of noble metal doping, it is imperative to perform quantitative structural characterization for SnOx thin films.In this study, we first demonstrated that doping with Pd can effectively increase the H2 gas sensitivity and decrease the response time of sol-gel derived SnOx thin films. Structural characterization of undoped and Pd-doped SnOx thin films was then shown. The grain size was measured using TEM, while the pore size was characterized using grazing-incidence small-angle x-ray scattering (GISAXS) technique. With synchrotron-based GISAXS facility at Advance Photon Source, we are able to monitor the pore size evolution in situ and in real time. The results convincingly show that doping of Pd could inhibit the grain coarsening and the growth of pores via “solute-drag” effect and by increasing the activation energy as well. Moreover, by using Knudsen gas diffusion model, the gas concentration profiles within the films were calculated based on the structural parameters obtained. H2 gas sensitivity of undoped and Pd-doped SnO2 thin films was evaluated in a semi-quantitative manner. The grain size and gas diffusion effects were considered collectively and the result indicated that although the microstructure of Pd-doped SnOx film is more favorable for gas sensing, the effect from the structural differences alone cannot explain one or two orders of magnitude change in the sensitivity. Furthermore, we employed the same strategy on investigating lower dimensional porous nanostructures. SnOx nanolines and nanodots were fabricated using “soft” electron beam lithography method. In order to enhance the scattering intensity from the pores, the nanostructures were patterned in an ordered manner. GISAXS model was then modified by considering two scattering sources: one is the correlation of the 2-D crystal-like SnOx nanopatterns; the other one is the pores inside those nanostructures. By fitting the GISAXS data, quantitative information of the nano-sized pores were obtained. Our study demonstrated that GISAXS is a unique tool for quantitatively characterizing porous oxide nanostructures, which will undoubtedly facilitate the understanding of structure-property relationships in semiconductor gas sensors.
OO5: GISAXS Studies of Biomolecular Materials, Complex and Structured Interfaces
Wednesday PM, December 03, 2008
Room 104 (Hynes)
2:30 PM - **OO5.1
Lipid Membrane-Assisted 2D Assembly of Bionanoparticles at Liquid Interfaces.
Masafumi Fukuto 1 , Suntao Wang 2 , Matthew Lohr 1 , Sumit Kewalramani 1 , Antonio Checco 1 , Lin Yang 2 Show Abstract
1 CMPMSD, Brookhaven National Lab, Upton, New York, United States, 2 NSLS, Brookhaven National Lab, Upton, New York, United States
Lipid monolayers at planar aqueous solution-vapor and solution-substrate interfaces provide an ideal platform for facilitating two-dimensional (2D) assembly of biomolecular nanoparticles like proteins and virus particles. In order to illustrate the utility and versatility of this approach to promoting the ordered assembly of nanoscale objects, we will describe the results of two of our recent studies: (i) the effects of surface biotin density on the 2D crystallization of the soluble protein streptavidin, and (ii) the formation of 2D arrays of virus particles. The structures of these systems have been probed by synchrotron x-ray scattering (GISAXS & XR), AFM, and optical microscopy measurements. We will also illustrate the capability of these techniques for in-situ characterization of structures at liquid interfaces.
3:00 PM - OO5.2
Diffraction from 2D Cholera Toxin Crystals Bound to Their Receptors in a Lipid Monolayer.
Majewski Jaroslaw 1 , Chad Miller 1 , Tonya Kuhl 2 , Erik Watkins 1 Show Abstract
1 Los Alamos Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Department of Chemical Engineering and Material Science, University of California, Davis, Davis, California, United States
Cholera toxin is highly efficient in taking over host organisms. To reap its destructive effects on the cell, these toxins must bind to and infiltrate the cellular membrane, a specialized and controlled barrier. The mechanism by which cholera toxin crosses the membrane remains unresolved. Utilizing grazing incidence x-ray diffraction (GIXD) the structure of cholera toxin (CTAB5) bound to its putative ganglioside receptor GM1 in a lipid monolayer at the air-water interface has been studied. This is one of very few proteins to be crystallized in two dimensions and characterized in a fully hydrated state. The observed GIXD Bragg peaks indicated cholera toxin was ordered in a hexagonal lattice and the order extended 600 Å to 800 Å. The pentameric binding portion of cholera toxin (CTB5) had improved in-plane ordering over the full toxin (CTAB5) especially at low pH. Out-of-plane diffraction (Bragg rod) analysis indicated pronounced changes the structure of the cholera toxin-lipid system under different pH conditions.
3:15 PM - OO5.3
In-situ Grazing Incidence Small Angle X-ray Scattering (GISAXS) Characterization of 2D Bacteriophage Arrays Deposited via Convective Assembly.
Carlee Ashley 1 , Darren Dunphy 1 , Eric Carnes 1 , David Peabody 2 , C. Jeffrey Brinker 1 3 Show Abstract
1 Chemical Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 2 Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico, United States, 3 Self-Assembled Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States
3:30 PM - **OO5.4
Evaporation-Induced Self-Assembly at Solid and Fluid Interfaces and Its Extension to Cell-Directed Assembly.
C. Jeffrey Brinker 1 Show Abstract
1 , Sandia National Laboratory/UNM, Albuquerque, New Mexico, United States
Evaporation of molecular precursors plus amphiphilic surfactants or nanoparticles at a solid or fluid interface drives self-assembly into robust, hybrid, organic / inorganic mesophases characterized by a structural periodicity on the nm length scale. Grazing incidence small angle x-ray scattering (GISAXS) provides a means to interrogate this evaporation-induced self-assembly (EISA) process in situ and to derive structural parameters of mesostructured films and monolayers. This talk will review EISA of surfactant-directed mesoporous films, 2D and 3D nanocrystal arrays, and viral particle monolayers and multilayers, highlighting structural insights gleaned using in situ and ex-situ GISAXS methods combined with other structural probes. A unifying theme is that maintenance of fluidity of the depositing film or monolayer promotes order and allows prediction of the emerging structure on the basis of thermodynamic expectations. We also study EISA of lipid-silica mesophases in the presence of living, energy-dissipating cells and show how cells actively re-organize the mesophase to form a unique bio/nano interface found to be cell specific. Use of the Advanced Photon Source and the National Synchrotron Light Source was supported by the U.S. Department of Energy Office of Basic Energy Sciences.
4:15 PM - OO5.5
Proteins on Surfaces Investigated by Microbeam Grazing Incidence Small Angle X-ray Scattering.
Ronald Gebhardt 1 , Manfred Burghammer 1 , Christian Riekel 1 , Charlotte Vendrely 1 , Stephan Roth 2 , Peter Mueller-Buschbaum 3 Show Abstract
1 , ESRF, Grenoble France, 2 , HASYLAB at Desy, Hamburg Germany, 3 , TU München, Physik Department E13, München Germany
Grazing incidence small angle scattering with a 1 micron x-ray beam (microGISAXS) has been applied to study the microstructure of casein and fibroin films. The method offers the possibility to detect different structural conformations frozen inside the film with high statistical relevance in a non-destructive way.In the case of the caseins, size changes of their association structures (casein micelles) have been investigated in calcium and rennet enzyme gradient films. The structural information obtained from the microGISAXS scans is correlated with the casein film morphology measured in parallel by optical microscopy. In the case of fibroin, the fiber formation during the drying process on a glass substrate has been investigated. The experimental data is analyzed and compared with simulations of the microGISAXS pattern.
4:30 PM - **OO5.6
Critical Dimension Small Angle X-ray Scattering as a Quantitative Metrology for Nanopatterning.
Christopher Soles 1 , Chengqing Wang 1 , Hyun Wook Ro 1 , Hae-Jeong Lee 1 , Kwan-Woo Choi 2 , Wen-li Wu 1 Show Abstract
1 Polymers Division, NIST, Gaithersburg, Maryland, United States, 2 , Intel, Hillsboro, Oregon, United States
The nanofabrication community, driven by in large by the semiconductor industry, has witnessed an exponential increase in the resolution of its state of the art lithographic techniques over nearly the past 40 years. Currently, features as small as 65 nm are routinely patterned in high volume production whereas low volume patterning techniques, such as electron beam lithography, are able to directly produce features on the order of (20 to 30) nm. With any manufacturing process, inspection tools are critical to ensure the quality of the patterning process throughout the production process. As the patterns become smaller, high resolution pattern shape measurements for quality control have generally become exceedingly difficult using either optical or electron beam inspection tools. However, an unintended consequence of this fairly recent transition into the regime of sub-100 nm patterning has been that it is now possible to use reciprocal space techniques with X-rays, such as small angle scattering or diffraction, as viable pattern shape metrologies. For periodic, sub-100 nm patterns it is fairly straight forward to obtain high quality scattering data that contains detailed information about the pattern shape. These methods are extremely attractive because, in principle, the reciprocal space measurements become easier as the periodicity and feature size becomes smaller. In this presentation we will review the recent developments of Critical Dimension Small Angle X-ray Scattering (CD-SAXS) as a viable pattern shape metrology for next generation lithographic patterning techniques. CD-SAXS is a transmission scattering technique where a periodic pattern acts as a diffraction grating for the X-rays. By analyzing the two dimensional scattering patterns from these gratings as a function rotation angle relative to the incident beam, we can quantify parameters such as periodicity, line width, space width, side wall angles, and side wall roughness. We will illustrate these techniques on several state of the art patterns with immediate technical relevance. In particular, we will emphasize the use of CD-SAXS and complimentary X-ray reflectivity measurements as quantitative tools to evaluate how different process parameters in nanoimprint lithography impact the quality of the imprinted nanostructures.
5:00 PM - OO5.7
Grazing Incidence Small Angle X-ray Scattering Studies of Nanopatterned Surfaces.
Tommy Hofmann 1 , Lin Yang 1 , Antonio Checco 1 , Ben Ocko 1 , Elizabeth Dobisz 2 Show Abstract
1 , BNL, Upton , New York, United States, 2 , Hitachi Global Storage Technologies, San Jose, California, United States
The search for new and improved magnetic storage devices has led to an interest in nano imprinting, a process in which a polymeric liquid is squeezed between a lateral ordered nanopatterned master and a substrate and subsequently cured/crosslinked with UV light. This emerging lithographic technique comes with fundamental technical and scientific challenges. How can the structure of the patterned master/printed replica be controlled, when the preferred dimensions of the bits (~20nm) are smaller than the Abbe limit of optical microscopy? What are the wetting properties of organic liquids on a nanopatterned surface? Are macroscopic wetting concepts still valid or is there a need for improved microscopic theories.Addressing these questions for a reference sample of ~20nm diameter posts arranged on a square pattern with a 40nm lattice spacing, we show that GISAXS measurements are a powerful tool for the nm-scale characterization of nanopatterned surfaces both dry and wet with controlled amounts of liquid. Scattering studies under grazing incident and detailed analysis based on a Distorted Wave Born Approximation reveal the important structural details such as the surface roughness and the geometric shape (size, inclination etc.) of the posts. Implementing a well defined temperature gradient between the sample and a separated reservoir of organic liquid (perfuoromethylcyclohexane) provides an insight in the wetting behavior for different undersaturated conditions (ΔT). The sensitivity of the GISAXS pattern on the amount and distribution of adsorbed liquid reveals detailed information about the wetting process.
5:15 PM - **OO5.8
Grazing Incidence Small Angle X-ray Scattering Studies of Two-Phase Thin Films.
Michael Toney 1 Show Abstract
1 , Stanford Synchrotron Radiation Laboratory, Menlo Park, California, United States
Two-phase thin films are of considerable technological and scientific interest. Such films can be used in inexpensive solar cells as bulk hetrojunctions (BHJs) and as models for electrocatalyst nanoparticles. BHJ solar cells are typically blends of an electron donor polymer and an electron accepting fullerene and have achieved efficiencies of 5% with the promise of low cost production. For efficient operation, the polymer and fullerene phase must separate on a 10-20 nm length scale (exiton diffusion length). Hence, the morphology of this two-phase film is tremendously important, but has not been empirically determined, largely as a result of the low contrast between the polymer and fullerene. Binary alloy (e.g. Cu-Pt) nanoparticles can potentially be used as the active electrocatalyst in Polymer Electrolyte Fuel Cells (PEMFCs), replacing the presently used pure Pt nanoparticles. Upon electrochemical “conditioning” (leaching or dealloying), these appear to form a Pt-rich shell-core structure, but due to the large distribution in particle sizes, these are difficult to carefully characterize. Thin films offer a model system to investigate this dealloying; in a film format, dealloying results in a two phase surface region (Pt-rich metal and voids). The morphology of this region affects the catalytic properties and understanding this relationship is important for developing better electrocatalysts.We have used GI-SAXS to study BHJ solar cells and dealloyed thin films designed to mimic alloy electrocatalysts. The BHJs studied are blends of phenyl-c71-butyric acid methyl ester (PCBM) and either poly(3-hexylthiophene) (P3HT) or poly(2,5-bis(3-tetradecyllthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). We observe phase segregation in these blend films on the 10 nm length scale that is related to solvent used for spin casting, the annealing, and the blending ratio. Interestingly, for PBTTT-PCBM no phase separation is found in 1:1 blends, which we attribute to an unexpected intercalation of the PCBM into the lamellar structure of PBTTT; phase separation is found for 1:4 blends. The dealloyed Pt(25)Cu(75) films show formation of a nanopoprous surface layer, where the pore/ligaments have length scales of about 1-2 nm; we do not observe a significant dependence of the nanoporous surface region on deallyoing, except for dealloying depth.
5:45 PM - OO5.9
Monitoring the Growth and Polymorphism of Organic Molecular Semiconductors.
Aram Amassian 1 , Vladimir Pozdin 1 , Alexios Papadimitratos 1 , Detlef Smilgies 2 , George Malliaras 1 Show Abstract
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York, United States
The growth, morphology, and structure of organic semiconducting thin films strongly influence the performance of devices, such as organic thin film transistors and sensors. The growth and polymorphism of pentacene were monitored in situ and in real time by grazing incidence wide-angle X-ray scattering (GIWAXS). Pentacene was deposited by vacuum sublimation on a variety of substrates, including clean SiO2 and SiO2 coated with insulating polymers. In situ GIWAXS measurements indicate that pentacene forms with a fiber texture with the c* axis normal to the substrate. Molecules stand nearly upright within the lattice on all insulating substrates, forming the well-known triclinic "thin-film" polymorph characterized by an out-of-plane interplanar spacing of 15.4 Å. Individual diffraction peaks (intensity, area, and width) have been analyzed in detail as a function of deposited thickness (determined from in situ quartz crystal microbalance measurements). The width of Bragg peaks in the out-of-plane direction is inversely proportional to the size of crystallites in the direction of growth. Our analysis reveals that while crystallites grow unobstructed on SiO2, their formation is frustrated on polymers after deposition of the first 10 to 15 monolayers, possibly leading to secondary nucleation of new crystallites above a certain thickness. Ex situ atomic force microscopy measurements on 45 nm-thick films reveal that films deposited on polymers exhibit very high island density with mean island spacing of three times greater on SiO2. Post-deposition annealing of the semiconducting films by exposure to a vapor of solvent molecules (a.k.a. solvent vapor annealing), resulted in phase transformation from the "thin film" phase into the "bulk" phase (out-of-plane interplanar spacing of 14.5 Å), as characterized by a change in the lattice parameters.
Benjamin Ocko Brookhaven National Laboratory
Jin Wang Argonne National Laboratory
Karl Ludwig Boston University
Thomas P. Russell University of Massachusetts
OO6: GISAXS Studies of Inorganic Thin Film and Nanostructured Growth
Thursday AM, December 04, 2008
Room 104 (Hynes)
9:30 AM - **OO6.1
Combined In Situ Gisaxs and Gixd Study of The Growth of Ge on Nominal and Patterned Si(001) Surfaces.
Gilles Renaud 1 , M. Richard 1 , T. Schulli 1 Show Abstract
1 , CEA-Grenoble, Grenoble Cedex 9 France
The growth of Ge on Si(001) follows the classical Stranski-Krastanow process: growth of a few monolayer-thick wetting layer followed by pyramid-like, then dome and super-dome islands, each characterized by specific sizes and facets . GISAXS and Grazing-Incidence X-Ray Diffraction were combined in situ, during the growth [2, 3], to characterize the 2D-3D transition as well as the islands shape, size, composition and strain, as a function of growth temperature, time and Ge flux, on different Si(001) substrates: either nominal, or patterned by lithography, or pattern by molecular bonding of twisted substrates followed by a chemical etch. GISAXS is used to characterize the substrate patterning, the 2D-3D transition and the type and size of islands, through their facet type and sizes . In parallel, GIXD, combined with the multiple anomalous scattering method, allows a precise identification of the 2D-3D transition, and then of the composition and strain state of the islands. Ge domes on patterned substrates are found to have the same composition as those deposited under identical conditions on nominal surfaces, but are more relaxed, thus having a smaller elastic energy. Dislocated superdomes are found to form earlier when the Ge flux is lowered, and their growth laws are discussed. B. Voigtländer, Surf. Sci. Rep. 43, 127 (2001). G. Renaud et al, Science 300, 1416 (2003). T. U. Schülli, M.-I. Richard, G. Renaud, V. Favre-Nicolin, E. Wintersberger and G. Bauer, Appl. Phys. Lett. 89, 143114 (2006) M.-I. Richard, T. U. Schülli, G. Renaud, E. Wintersberger, G. Chen, G. Bauer and V. Holy, submitted.
10:00 AM - OO6.2
In Situ Detection of Si Nanoclusters by Small Angle X-ray Scattering during High Rate and Low Temperature Silicon Epitaxy by Mesoplasma Chemical Vapor Deposition.
Makoto Kambara 1 , Diaz Jose Mario 1 , Toyonobu Yoshida 1 Show Abstract
1 Department of Materials Engineering, The University of Tokyo, Tokyo Japan
A gradual change in the silicon film morphology from polycrystalline to epitaxial has been observed during mesoplasma CVD with an increase in the RF input power. Interesting features of this epitaxial growth include that the deposition rate increases linearly with silane gas flow rates while it remains as high as 40 nm/s even if the substrate temperature is lowered to 360 C. It is further noted that these epitaxial films exhibited Hall mobility of around 280 cm2/V-s independently of the deposition rates and substrate temperatures. With these in mind, to understand the role of the growth precursors, we have attempted small angle X-ray scattering for in-situ detection of nano-sized silicon clusters that could form upon condensation of the silicon vapor within the boundary layer between plasma and substrate during high rate and low temperature epitaxy. In this lab-scale scattering system assembled with the plasma reactor, Cu-Kα 300µm dia. X-ray beam, after slits and collimator, was aligned to pass within the plasma / substrate boundary and the scattered X-ray profile was collected by 2D-PSPC at a plasma-detector distance of 1.1m through He path after Ni filter. The size distributions of the scatterers, quantified by the GNOM, have shown that the primary modal size for polycrystalline film deposition ranges from 2.5–3 nm, whereas that for the epitaxy decreases slightly to 2.0–2.5 nm. For both polycrystalline and epitaxial conditions, Kratky plot exhibit a pronounced primary maximum peak around 0.8 nm-1, indicating that the scatterers are fundamentally spherical or globular with a dominant cluster size of around 2.6 nm, irrespective of the film microstructure so deposited. However, the secondary and tertiary peaks were evident around 0.6 and 1.0 nm-1, respectively, when polycrystalline film was deposited. This suggests that the formation of larger-sized clusters even at that much small amount plausibly affects the epitaxial to polycrystalline transition. Furthermore, no apparent plateau was observed in the Porod plots for both cases. Given that the scatterers are globular or spherical in shape, Porod representation suggests the possibility of a diffuse electron density distribution near the nanocluster surface, i.e. a loosely bound structure at least in vicinity of the cluster surface. In summary, in-situ detection with SAXS has suggests that thermally-activated nano-sized silicon clusters could be formed upon condensation and possibly facilitate fast rate surface migration of the constituent silicon atoms on the film, despite low temperature and adhesive growth mode during mesoplasma epitaxy.
10:15 AM - OO6.3
Dynamics of Carbon Nanotube Forest Growth Revealed by in Situ X-ray Scattering.
A. John Hart 1 , Eric Verploegen 2 , Eric Meshot 1 , Sameh Tawfick 1 , Jeremy Ng 1 Show Abstract
1 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
We investigate growth of vertically-aligned carbon nanotube (CNT) forests by in situ X-ray scattering, and thereby elucidate the dynamics of catalyst particle coarsening, forest self-organization, temperature- and reactant-driven CNT structure evolution, and growth termination. A custom-built atmospheric-pressure CVD reactor featuring a resistively-heated substrate platform is mounted directly on a motorized stage in the synchrotron beamline (G1 at Cornell High Energy Synchrotron Source), enabling real-time grazing incidence (GI-SAXS) and transmission (SAXS, WAXS) scattering studies. Simultaneous laser measurement of the forest height captures the growth kinetics, the heated platform enables rapid temperature changes 100 oC/s during annealing and growth, and the reactant gas is independently pre-treated to create active carbon species. Starting with a catalyst thin-film of Fe/Al2O3 on Si, we observe rapid coarsening of Fe at temperatures as low as 550 oC in H2, and study the kinetics of particle coarsening in both reducing and inert atmospheres. CNT diameter and growth rate are directly proportional to the substrate temperature, and tuning of annealing and growth conditions using SAXS-derived diameter measurements reveals that CNT forests with mean diameters ranging from 5-30 nm can be grown from the same starting catalyst film thickness. Ex situ spatial mapping of forests reveals how CNT diameter, alignment, and areal density evolve with continued growth, and in combination with surface analysis (AFM, XPS) suggests how the catalyst particle size and structure evolve under hydrocarbon exposure. Growth self-terminates abruptly, accompanied by a sudden loss of alignment at the CNT-substrate interface; this appears to be a universal chemical and/or mechanical signature in our experiments. Our apparatus and investigation technique reveal a broader understanding of the limiting mechanisms of CNT forest growth, and can be extended to other self-assembled systems such as nanoparticle films and semiconducting nanowires, as well as provide direct insight for engineering application-oriented characteristics of nanostructured materials. A.J. Hart, E. Verploegen, E.R. Meshot, S. Tawfick, S. Han, J. Ng. Dynamics of carbon nanotube forest growth revealed by in situ X-ray scattering, submitted for publication. B.N. Wang, R.D. Bennett, E. Verploegen, A.J. Hart, R.E. Cohen. Characterizing the morphologies of mechanically-manipulated Multi-Wall Carbon Nanotube Films by Small-Angle X-ray Scattering, J. Physical Chemistry C 111(48):17933-17940, 2007, http://dx.doi.org/10.1021/jp071798c.  B.N. Wang, R.D. Bennett, E. Verploegen, A.J. Hart, R.E. Cohen. Quantitative Characterization of the Morphology of Multi-Wall Carbon Nanotube Films by Small-Angle X-ray Scattering, J. Physical Chemistry C 111(16):5859-5865, 2007, http://dx.doi.org/10.1021/jp068895a.
10:30 AM - **OO6.4
Using In-situ X-ray Reflectivity and Diffuse Scattering to Probe Surface Morphology and Kinetics During Thin Film Growth.
Arthur Woll 1 , Aram Amassian 2 , Göokhan Arikan 3 , Tushar Desai 4 , John Ferguson 2 3 , Sukwon Hong 4 , Aaron Vodnick 2 , Joel Brock 3 5 , James Engstrom 4 Show Abstract
1 Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York, United States, 2 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 3 Cornell Center for Materials Research, Cornell University, Ithaca, New York, United States, 4 School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States, 5 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States
11:30 AM - **OO6.5
Real-time Studies of Roughness Evolution and Pattern Formation During Thin Film Growth and Surface Processing.
Randall Headrick 1 Show Abstract
1 Department of Physics and Materials Science Program, University of Vermont, Burlington, Vermont, United States
In-situ Grazing Incidence Small-Angle X-ray Scattering (GISAXS) utilizing synchrotron sources in the hard x-ray regime (5 – 30 keV) has become a powerful tool for the discovery and characterization of time-dependent effects at length scales ranging from atomic dimensions to microns. A main thrust of our research has been the analysis of amorphous surfaces and interfaces with laterally correlated features. This research depends on analysis of the roughness spectrum of the surface (i.e. the Power Spectral Density), which is closely related to the in-plane scattering pattern that is measured by GISAXS. Experimental details related to the use of a position-sensitive strip detector operating in pulse counting mode to collect the in-plane spectrum will be discussed, as well as complementary techniques such as in-situ x-ray reflectivity. Two experimental examples will be discussed: (1) the formation of lateral patterns such as ripples and dots on simple oxide surfaces (AL2O3 and SiO2) by ion bombardment, (2) Evolution of surfaces and formation of interfaces during sputter deposition of amorphous films and multilayers, particularly the WSi2/Si multilayer system.
12:00 PM - OO6.6
Surface Roughness Evolution During the Sputter Deposition of WSi2 Amorphous Films by Real-Time GISAXS.
Lan Zhou 1 , Hua Zhou 1 , Yiping Wang 1 , Randall Headrick 1 , Albert Macrander 2 , Nathalie Bouet 3 , Karl Ludwig 3 Show Abstract
1 physics department, university of vermont, Burlington, Vermont, United States, 2 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States, 3 Department of Physics, Boston University, Boston, Massachusetts, United States
Sputter deposition is a widely-used process for making thin films and industrial coatings for an enormous range of applications. However, the detailed mechanisms of roughening and smoothing in the growth processes are not known. Grazing-Incidence Small-Angle X-Ray Scattering (GISAXS) provides the real-time monitoring of the evolution of the Power-Spectral Density (PSD) during thin films growth processes, which gives insight into the smoothing and roughening mechanisms inherent to the growth process. In this work, by reducing the background Ar pressure, the surface morphology of WSi2 is changed from rough to ultra-smooth. Corresponding changes in GISAXS intensity profiles as a function of pressure and film thickness are used to monitor the PSD under different growth conditions. During the early stage of growth, there is a pronounced surface lateral correlation appearing in the high-frequency region ( ~3 nm-1) which may indicate clusters distributed on the surface. During later stages of the growth, the surface roughness spectrum of sputtered WSi2 thin films closely resembles the theoretical power spectral density curve for a simple linear growth model based on the Mullins model, with shot noise as a roughening mechanism.
12:15 PM - OO6.7
In Situ and Real-time Comparative Study of Ga Adsorption/Desorption On Sapphire Surfaces.
Nathalie Bouet 1 , Eitan Anzenberg 1 , Christopher Sanborn 1 , Karl Ludwig 1 Show Abstract
1 Physics Department, Boston University, Boston, Massachusetts, United States
Supported nanoparticles are one of the most promising fields for the development of new devices in fields such catalysis, optics, magnetic data storage, optoelectronics... For all these applications, the control of the properties is strongly related to the size, distribution, morphology and crystalline structure of the nanoparticles on the surface of the substrate. For self-assembled nanoparticles, this control can be done thanks to a good understanding of the processes involved during the growth. In the case of GaN, plasma-assisted MBE (PA-MBE) allows one to grow high quality films as well as nanostructures [1,2]. But because PA-MBE is an atomic deposition process, the main step is the Ga deposition on the substrate's surface. However only a few in-situ studies are reported on the process of adsorption of Ga and subsequent growth on surfaces . Our group has recently reported an adsorption/desorption study of Ga on c-sapphire under high flux of Ga . In the work presented here, we performed in situ real-time grazing incidence small-angle scattering (GISAXS) and fluorescence X-ray spectroscopy experiments to study the Ga adsorption/desorption kinetics under a low flux of Ga surfaces to focus on the early stages of the Ga adsorption on a-plane and c-plane oriented sapphire. Because temperature is the major key to control the sticking of the atoms arriving on the surface, atomic and aggregates diffusions, density of nanoparticles as and atomic desorption, the effect of substrate temperature has been investigated as well. Sticking coefficients and desorption energies have been deduced for the 2 types of surface from the fluorescence measurements. It is found that the adsorption/desorption behaviors are strongly influenced by both the nature of the substrate and the temperature. Exposure of the substrate to a low pressure vapor of Ga from an effusion cell was conducive to the formation of droplets for the two kinds of substrates as evidenced by GISAXS. However, it appears that, under similar deposition conditions, the size and density of the droplets and/or growth stages observed are shifted in temperature between the 2 sapphire substrate orientations studied.The combination of fluorescence with the GISAXS experiments allows us to examine the formation and morphological characteristics of Ga droplets formed as a function of the Ga deposition conditions. 1. H. Sekiguchi, T. Nakazato, A. Kikuchi and K. Kishino, Journal of Crystal Growth 300 (1), 259-262 (2007)2. C. Adelmann, B. Daudin, R.A. Olivier, G. A. D. Briggs and R. E. Rudd, Physical Review B 70, 125427-125434 (2004)3. G. Koblmuller, R. Averbeck, H. Riechert, and P. Pongratz, Physical Review B 69, 035325-035333 (2004)4. Y. Wang A. S. Özcan, K.F. Ludwig, A. Bhattacharyya, Journal of Applied Physics, in press
12:30 PM - OO6.8
Temperature Dependence of Surface Morphology Development During the Ion Bombardment of Si with Mo Seeding.
Karl Ludwig 1 , Gozde Ozaydin-Ince 1 2 Show Abstract
1 Physics, Boston University, Boston, Massachusetts, United States, 2 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Using real-time Grazing Incidence Small-Angle Scattering (GISAXS), we have examined the kinetics of surface morphology development during the normal-incidence Ar+ ion bombardment of Si with Mo seeding. These experiments used a 500 eV ion beam with a flux of approximately 7 microamp/cm2. At temperatures below approximately 400 C, the surface is amorphized during bombardment as seen by RHEED. In this regime, nanodot structures form spontaneously on the surface and reach a steady state. Between room temperature and 400 C, the overall roughness for a given ion fluence decreases slightly with increasing temperature, consistent with the existence of thermal smoothening. In the temperature range 400-650 C, however RHEED shows a crossover to a crystalline surface during bombardment. Concomitantly there is a fundamental change in the behavior of the surface morphology evolution. Above approximately 650 C, nanodots no longer form and instead a rapidly coarsening correlated roughness develops on longer length scales. The growth of roughness at these temperatures is quantitatively similar to the observed in the absence of seeding, suggesting that here the surface morphology development is dominated by an inherent instability of the bombarded crystalline Si surface.This work was partially supported by DOE DE-FG02-03ER46037 and NSF DMR-0507351.
12:45 PM - OO6.9
Characterization of Long- and Short-period Soft X-ray Multilayer Mirrors by Grazing-incidence Small-angle X-ray Scattering.
Peter Siffalovic 2 , Livia Chitu 2 , Eva Majkova 2 , Matej Jergel 2 , Stefan Luby 2 , Guenther Maier 1 3 , Jozef Keckes 3 , Andreas Timmann 5 , Stefan Roth 5 , Toshihide Tsuru 4 , Tetsuo Harada 4 , Masaki Yamamoto 4 Show Abstract
2 , Institute of Physics, Slovak Academy of Sciences, Bratislava Slovakia, 1 , Materials Center Leoben Forschung GmbH, Leoben Austria, 3 , Erich Schmid Institute for Materials Science, Leoben Austria, 5 , HASYLAB / DESY, 22603 Hamburg Germany, 4 , IMRAM, Tohoku University, Aobaku, Sendai 980-8577 Japan
The soft X-ray multilayer mirrors centred at 13 nm and in the water window (2.5-4.5 nm) play and important role in applied science and emerging industrial applications. A fast and non-destructive diagnostics of buried layers and interfaces is required for ex situ and in situ deposition control. The grazing-incidence small-angle X-ray scattering (GISAXS) together with X-ray reflectivity provide sufficient information on layer thickness, interface RMS roughness, vertical correlation length and lateral autocorrelation functions of interfaces. We measured Mo/Si multilayer mirrors prepared by various deposition techniques such as physical vapour deposition (PVD), ion beam assisted deposition (IBAD), ion beam sputtering (IBS) and magnetron sputtering. In GISAXS simulations we used autocorrelation function proposed by Sinha, fully defined by the RMS roughness, lateral correlation length and Hurst parameter. The GISAXS data allow reliable estimation of autocorrelation functions of interfaces in contrast to the coplanar X-ray reciprocal maps suffering from the small accessible lateral q space range. The GISAXS measurements of short-period multilayer mirrors like Co/C and Cr/C with low roughness values show absorber layers consisting of laterally uniformly spaced clusters with no vertical correlations between adjacent layers. The GISAXS measurements were performed on Hamburger synchrotron, HASYLAB and on table-top system Nanostar, Bruker. The GISAXS measurements done with microfocus X-ray source yield comparable results to the synchrotron one. The X-ray microfocus sources present an interesting alternative for in situ vacuum deposition control of thickness and roughness simultaneously.