Symposium Organizers
Fred B. McCormick 3M Company
Junji Kido Yamagata University
John Rogers University of Illinois, Urbana-Champaign
Shizuo Tokito NHK Science & Technical Research Laboratories
L1: Electrical, Mechanical and Optical Properties of Films and Components for Next Generation Displays
Session Chairs
Tuesday PM, April 18, 2006
Room 3003 (Moscone West)
9:30 AM - L1.1
A Next Generation TCO Material for Display Systems: Molybdenum Doped Indium oxide Thin Films.
E. Elamurugu 1 , A Marques 1 , R Martins 1 , E Fortunato 1
1 Department of Materials Science, University of New Lisbon, Monte de Caparica, Setubal, Portugal
Show AbstractTransparent conducting oxide (TCO) materials are attracting more attention repeatedly for the reason that they are broadly used in many fields in general and display systems in particular. Many conventional TCOs such as tin doped indium oxide (ITO), tin oxide, zinc oxide, cadmium oxide and other materials have been studied extensively. Work by Meng et al. [Thin Solid Films, 394; 2001: 219] on molybdenum doped indium oxide (IMO) has highlighted it as a novel TCO material. IMO could well be considered as the next generation TCO material since they possess very high mobility with high transmittance and conductivity. Many techniques have been applied to study this material and very recently a technique called channel spark ablation [J. Vac. Sci. Technol. A, 23; 2005: 1350] has been reported. Hitherto, IMO has been prepared at 250° C or higher temperatures and there is paucity of reports on attempts to prepare at room temperature. Toward achieving this, we have carried out preliminary studies [to be presented at 2005 MRS Fall meeting; partial work communicated to the journal Vacuum is under revision] on these films rf sputtered at room temperature as a function of oxygen volume percentage (O2 vol. %). We found that the minimum O2 vol. % (3.5 %; O2 partial pressure of ~1.5 × 10-5 mbar at the flow of 0.5 sccm) as the most effective; all the films were sputtered with low power (40 W) for 30 minutes. Although the as-deposited amorphous films were highly transparent (> 90 %) in the visible range, the films were highly resistive. In an effort of increasing the conductivity the present study was carried out. The films were deposited for lesser time (10 minutes) and we found that the sheet resistance dropped by 4 orders of magnitude. The sputtering time has been varied from 2.5 to 20 min with an increasing step of 2.5 min. The sputtering power has been increased at a step of 20 W until 200 W. The thickness of the films found varied between 50 – 400 nm. All the films were sputtered from an In2O3 (95 wt. %): Mo (5 wt. %) spherical target of 2” in diameter and 2 mm thick. Flow of oxygen was fixed constant at 0.5 sccm (partial pressure of ~1.5 × 10-5 mbar) and argon at 30 sccm (partial pressure of ~2.9 × 10-3 mbar). The deposition pressure was fixed at 6.0 × 10-3 mbar. All the as-deposited films were characterized for their structural (XRD, SEM, AFM), electrical (Hall measurements and conductivity measurements) and optical (transmittance spectra) properties. The films were found to be amorphous in nature with high visible transmittance (> 90 %) and low resistivity (ranging from 10-3 – 10-4 Ω-cm).
9:45 AM - L1.2
Effect of Parameters on Indium Zinc Oxide Films Deposited by DC Magnetron Reactive Sputtering Method.
Do-Geun Kim 1 , Chang-Ha Park 1 , Sunghun Lee 1 , Dong-Ho Kim 1 , Gun-Hwan Lee 1
1 Surface Technology Research Center, KIMM (Korea Institute of Machinery & Materials), Changwon, Gyeongnam, Korea (the Republic of)
Show Abstract Indium Zinc Oxide (IZO) films were deposited using different oxygen contents and substrate temperatures by DC magnetron reactive sputtering method. With addition of small amount of oxygen gas, the characteristic properties of amorphous IZO films were improved and the specific resistivity was about 4.8×10-4 Ωcm. Change of structural properties according to the deposition temperature was also observed with XRD, SEM, and AFM. Films deposited above 300 °C were found to be polycrystalline. Surface roughness of the films was increased due to the formation of grains on the surface. Electrical conductivity became deteriorated for polycrystalline IZO films due to the phase separation of In2O3 and ZnO of IZO films prepared above 300 °C. Consequently, high quality IZO films could be prepared by dc sputtering with O2/Ar of 0.03 and deposition temperature in range of 150~200 °C; a specific resistivity of 3.4×10-4 Ωcm, an optical transmission over 90% at wavelength of 550 nm, and a rms value of surface roughness about 3 Å.
10:00 AM - L1.3
Electrical And Optical Properties Of GZO/HfO2/GZO Transparent Mim Capacitors.
Byung du Ahn 1 , Jong Hoon Kim 1 , Dong Hua Li 1 , Sang Yeol Lee 1
1 Electrical and Electronic Engineering, Yonsei University , Seoul Korea (the Republic of)
Show AbstractGa doped ZnO (GZO)/HfO2/GZO metal-insulator-metal (MIM) transparent capacitors were prepared by pulsed laser deposition (PLD) on glass substrate. Structural, optical, and electrical properties of these films were analyzed in order to investigate their dependence on oxygen pressure, substrate temperature and rapid thermal annealing (RTA). Capacitance-voltage (C-V), current-voltage (I-V) measurements, X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-NIR grating spectrometer are used to analyze the properties of GZO/HfO2/GZO MIM transparent capacitors.
10:15 AM - L1.4
Low Temperature (<150°C) Deposition of Sillicon Nitride Films on Plastic Substrates by Catalytic CVD Technique
Wan-Shick Hong 1 , Chul Lai Cho 1 , Sung Hyun Lee 1
1 Electronics Engineering, Sejong University, Seoul Korea (the Republic of)
Show Abstract10:30 AM - L1.5
Mechanical and Optical Properties of SiNx Barrier Layers Deposited at 250oC on a Clear Polymer Substrate.
Kunigunde Cherenack 1 , I-Chun Cheng 1 , Alex Kattamis 1 , Sigurd Wagner 1
1 , Princeton University, Princeton, New Jersey, United States
Show AbstractInterest is widespread in flexible thin-film transistor backplanes made on clear polymer foil, which could be universally employed for a variety of applications. The quality and stability of amorphous silicon thin-film transistors (a-Si:H TFTs) improves with increasing process temperature. Therefore, optically clear plastic (CP) substrates are desired that tolerate high process temperatures. The first step in a-Si:H TFT fabrication on a polymer is the deposition of a planarizing barrier and adhesion layer. For this purpose we have been using silicon nitride (SiNx) grown by plasma-enhanced chemical vapor deposition (PECVD). This study discusses in detail the substrate preparation and SiNx deposition for process temperatures in the vicinity of 250oC . The CP substrates are first cured at high temperatures to reduce additional shrinkage during processing. We study the mechanical strain in the SiNx film on the CP substrate, as a function of RF power. Earlier work has shown that SiNx films deposited at low RF power are under tensile strain, and become increasingly compressed as the deposition power is raised. We aim to minimize the mismatch strain between film and substrate, to keep the film/substrate composite flat and avoid mechanical fracture and peeling. (Small mismatch strain produces curvature, large mismatch strain causes cracking.) A series of experiments is carried out to investigate the cracking of 300nm thick SiNx layers at various deposition powers. We have observed different cracking patterns and densities at various powers, where the cracking is less pronounced for low RF deposition powers. In addition, the SiNx layer thickness for crack onset is being investigated by depositing SiNx layers of varying thickness on the CP substrates. By also varying the RF deposition power, the stress in the SiNx film is varied. Our target is to find the correct RF deposition power and film thickness combination to deposit crack-free SiNx films. We will include a study of the optical transmission spectrum with emphasis on the 400-nm wavelength region, which is important for self-alignment during TFT fabrication.
10:45 AM - L1.6
NASICON-like Phases in ScPO4-Na3PO4-Li3PO4 Quasiternary System.
Zimina Galina 1 , Mariya Zhuravleva 1 , Ruslan Zakalyukin 1 , Andrey Novoselov 1 , Valeriy Fomichev 1
1 , Lomonosov Moscow State Academy of Fine Chemical Technology, Moscow Russian Federation
Show AbstractL2: Patterning and Manufacturing Methods for Next Generation Displays
Session Chairs
Tuesday PM, April 18, 2006
Room 3003 (Moscone West)
11:30 AM - L2.1
Patterning Elastically Stretchable Interconnects for Flexible Displays.
Joyelle Jones 1 , S. Lacour 1 , Sigurd Wagner 1
1 Electrical Engineering, Princeton University, Princeton, New Jersey, United States
Show AbstractCurrent development of flexible displays focuses on cylindrical deformation produced by bending or rolling. With proper design, the maximum strain that the device materials must withstand can be kept below the critical fracture strain of a few tenths of a percent. However, if planar circuits are to be shaped plastically or elastically, to make initially flat circuits to displays or other electronic devices of arbitrary surface topographies, the strain may exceed tens of percent. Examples are the dashboard of a car or the surface of a prosthetic arm. Preventing device fracture on such surfaces requires a fundamentally new approach.Taking advantage of recently discovered stretchable metallization, we are fabricating elastically stretchable interconnects that are robust to elongation beyond 10%. Because the elastomeric silicone substrate used for stretchable metal films swells in clean room solvents, so far the metal has been patterned by overlay or dry resist shadow masks. These patterning techniques kept line widths above 100 µm. Here we report that photolithographic patterning is possible if coupled with dry processing. We now have patterned elastic metal lines with widths ranging from 10 µm to 100 µm. The interconnects are made of 5nm/75nm chromium/gold films on a 1mm thick poly dimethylsiloxane (PDMS) substrate. While all interconnects are elastically stretchable, when wider than 50 µm they remain electrically conductive while strained up to 20%, but only up to 10% when narrower than 50µm. The change of electrical resistance R with strain E, dR/dE, rises as the width of the interconnects decreases. When cycled 5 to 10 times, the samples remain electrically conducting. We will describe basic observations of stretchability, the fabrication and electro-mechanical testing of the interconnects, and their morphology before, during, and after stretching.
11:45 AM - L2.2
Fine-feature Patterning of Thin-film Transistor Arrays by Digital Lithography
William Wong 1 , Eugene Chow 1 , Rene Lujan 1 , Scott Limb 2 , Beverly Russo 2
1 Electronic Materials and Devices Laboratory, Palo Alto Research Center, Palo Alto, California, United States, 2 Hardware Systems Laboratory, Palo Alto Research Center, Palo Alto, California, United States
Show AbstractDeveloping an inexpensive and simplified patterning process, compatible with low-melting point flexible substrates, would enable low-cost, large-area electronics for displays, sensors, and evolving technologies such as electric paper. The spatial resolution and small drop volume of jet-printing methods present opportunities to simplify and reduce the cost for conventional large-area electronic device fabrication. A novel digital-lithographic method, in which an electronically generated and digitally aligned etch mask is jet-printed onto a process surface has been demonstrated in fabricating a-Si:H thin-film transistor (TFT) array backplanes for reflective display applications.In some cases, the minimum drop size of jet-printed features may be too large for high-performance applications. The digital lithographic process, having minimum printed features of ~40 microns, allows for very accurate and precise drop placement control. By using this spatial control, fine feature gaps (10-15 microns) can be patterned over large areas. In this talk, we will describe the fabrication of fine-feature TFT devices using a jet-printed etch mask process with conventional semiconductor materials. Channel lengths as short as 10 microns were fabricated using the digital lithographic process. In combination with digital lithography, a low temperature a-Si:H based TFT deposition process (T<150°C) was used to fabricate TFT devices having threshold voltages of 2-3 V and on/off ratios of 108, and field effect mobilities of 1 cm2/Vs,comparable to conventionally processed a-Si:H TFT devices. Pixel design using digital lithographic processing and integration of the flexible TFT array backplane with display media will also be discussed.
12:00 PM - L2.3
Conducting Polymer as Transparent Electric Glue and Its Application in Roll-to-Roll Fabrication of Flexible Electronic Devices.
Jianyong Ouyang 1 , Yang Yang 1
1 Department of Materials Science and Engineering, University of California, Los Angeles (UCLA), Los Angeles, California, United States
Show AbstractFlexible electronic devices, including organic electronic devices and devices using nanomaterials or biomaterials, have tremendous application in a variety of areas and have made significant progress. They have many merits including high mechanical flexibility and low fabrication cost. The conventional way to fabricate these flexible devices is through a bottom-to-up process, but it is not the most efficient way. Roll-to-roll coating process is the most efficient fabrication way and greatly lowers fabrication cost. However, an efficient roll-to-roll fabrication process has not been demonstrated. The challenge lies in the lamination of two films electrically and mechanically. Some methods have been demonstrated to laminate two organic films, but these methods are only for special materials or not practical. In this meeting, we will report three simple approaches to develop solvent-free electric glue using conducting polymer. This electric glue exhibited a conductivity of 10^2 S cm^-1, and could effectively laminate various materials electrically and mechanically. The organic electronic devices fabricated through a lamination process using this electric glue exhibited high performance.
12:15 PM - L2.4
Printable Optoelectronics: Processing Parameter Optimization for Improved Lifetime of Light Emitting Displays on Flexible Substrates.
Melissa Kreger 1 , Devin MacKenzie 1 , Yuko Nakazawa 1 , Jian Ping Chen 1 , Sue Carter 2 1 , Vung Vu 1 , Janie Breeden 1 , Eric Jones 1 , Matt Wilkinson 1
1 , Add-vision, Inc., Scotts Valley, California, United States, 2 Physics Department, University of California Santa Cruz, Santa Cruz, California, United States
Show AbstractWe present a fabrication process for inexpensive optoelectronic devices on flexible PET substrates. The objective of this research was to improve the electroluminescence (EL) stability and operating voltage of screen-printed light emitting displays. We examine how the EL properties depend on factors such as substrate cleaning, patterning, ink processing and deposition, annealing and solvent removal conditions. Challenges associated with ink formulation and phase separation, will be correlated to film morphology and EL uniformity. We also explore the relationship between charge transport and doping of the light emitting polymer (LEP) layers. The EL stability and operating voltage of the display prove to be strongly correlated to the nature and quantity of dopants incorporated into the structure. We fabricate a matrix of device structures including spin cast LEP with evaporated Silver, spin cast LEP with printed Silver, printed LEP with evaporated Silver and printed LEP with printed Silver. From this matrix we can understand correlations between phase separation and EL uniformity, interfacial morphology and operating voltage, and the critical relationship between solvent removal and device lifetime. Results for light-emitting electrochemical cells created by a fully screen-printed process including J-V-L characteristics, external quantum efficiency and lifetimes are presented. We show that turn-on time is strongly affected by annealing conditions. In addition, we discuss how the operating voltage changes over the lifetime of the display. Lifetime measurements show EL degradation is correlated to insufficient solvent removal from LEP and/or printed Silver layers.
12:30 PM - **L2.5
Large Area Printable Electronics: Materials and Processes
Graciela Blanchet 1
1 Central Sciences and Engineering Experimental Station, DuPont, Wilmington, Delaware, United States
Show AbstractOrganic electronic systems offer the possibility of lightweight, flexibility and large area coverage, properties not easily achievable with standard silicon technology, and at potentially lower manufacturing costs. DuPont has focused on the development of conducting and semiconducting organic materials that allow for the printing of active and passive electronic devices. A number of groups have focus in improving device performance by designing organic semiconducting materials of higher mobility. We demonstrate an alternative path for achieving high transconductance organic transistors in spite of relatively large source to drain distances. The method, based on creating sub-percolating conducting networks, would enable the printing of sub-micron features with conventional commercial engines. The improvement of the electronic characteristic of such a scheme is equivalent to a 60-fold increase in effective mobility without reduction of the on/off ratio. These conducting and semiconducting composites are compatible with various large area printing processes such as thermal and ink jet. However, the manufacturing of complex multi-layer circuits over large areas in a reel-to-reel configuration has been one of the driving forces in the organic electronics field. We are currently evaluating the feasibility of micro-contact printing as a path to high-resolution reel-to-reel electronics. Thus extending flexography into the high-resolution arena. Unlike conventional lithography, micro-contact printing; not requiring sacrificial resists, developers, and etchants; maybe compatible with a wider range of materials and substrates currently utilized in plastic electronics.
L3: Organic Light Emitting Diodes
Session Chairs
Tuesday PM, April 18, 2006
Room 3003 (Moscone West)
2:30 PM - L3.1
Highly Efficient Phosphorescent Materials Coupled Dendrimer Host Through Intramolecular Energy Transfer.
Tae-Hyuk Kwon 1 , Myoung Ki Kim 1 , Jongchul Kwon 1 , Chang-Lyoul Lee 2 , Jang-Joo Kim 2 , Su-Jin Park 3 , Dae Yeup Shin 3 , Jong-In Hong 1 4
1 Chemisty, Seoul National University, Seoul Korea (the Republic of), 2 School of Materials Sciences and Engineering, Seoul National University , Seoul Korea (the Republic of), 3 Corporate R&D Center, Samsung SDI, Yongin Korea (the Republic of), 4 Center for Molecular Design and Synthesis, KAIST, Daejon Korea (the Republic of)
Show Abstract In this study, we report a new phosphorescent system for organic light-emitting diodes (OLED), phosphorescent dopant coupled dendrimer host, retaining advantages of general dendrimer, such as high efficiency and easy accessibility for solution processing as well as increasing the efficiency through intramolecular energy transfer in addition to controlling over intermolecular interactions which leads to luminance quenching. The host is coupled with dopant by a non-conjugated benzyl ether linker in this system. This Hopant system (host-dopant conjugate) with various generation have been synthesized. The benzyl ether linker was introduced to keep the photophysical properties of both donor and acceptor. We compared the photophysical properties of Hopant with only dopant molecule and dopant-host blending system. The Hopant, in which host was coupled with dopant by non-conjugated bridge, show higher PL intensity in dilute solution than that of dopant only and the blended system by the efficient intramolecular triplet-triplet energy transfer from host to dopant in addition to less luminance quenching. We expect that this Hopant system will be very useful for the application to the large-panel displays in OLEDs
2:45 PM - **L3.2
Recent Developments in High Efficiency Phosphorescent OLEDs.
Jason Brooks 1
1 , Universal Display Corporation, Ewing, New Jersey, United States
Show AbstractOLED displays are now entering the marketplace as an ideal technology for the manufacture of ultra thin, high resolution, low power consumption full color displays, with fast video response rates and wide viewing angles. They are fabricated by depositing very thin films of organic materials to form bright, self-emissive light producing elements with fast response times that can be grown on a variety of large area substrates such as glass, plastic or metal foil. The incorporation of highly emissive heavy-atom phosphorescent materials in OLEDs can allow for all electrically generated excited states to emit with high efficiency from the triplet state of the phosphorescent chromophore, approaching the theoretical limits of device efficiency. Therefore phosphorescence is a key component for lowering the power consumption of the display and has demonstrated saturated RGB and white emission with long device lifetime. Our recent progress in material development, device architecture and device lifetime will be discussed.
3:15 PM - **L3.3
Ultrahigh Efficiency Polymer LEDs.
Yang Yang 1
1 Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California, United States
Show AbstractIn this presentation, a general method to improve PLED efficiency will be reported. By adapting a proper interfacial layer between Al (cathode) and LEP, we are able to boost the PLED performance by a factor of two to three. For example, by adapting Ca(acac)2 layer, green PLEDs reaching 30lm/watt; and by using a Cs2(CO)3 layer, white PLEDs reaching 16lm/watt have been demonstrated, respectively. The lifetime test results of those devices are also very stable. This approach opens a new direction for achieving ultrahigh efficiency PLEDs with low cost solution processing for indoor lighting and displays. The mechanism of our high efficiency PLEDs will also be discussed.
3:45 PM - L3.4
High-Efficiency White OLEDs Using Wide-Energy Gap Charge Transport Materials and Phosphorescent Emitters
Junji Kido 1 2 , Nobuhiro Ide 2 , Daisaku Tanaka 2 , Yuya Agata 2 , Takashi Takeda 2
1 Polymer Science and Engineering, Yamagata University, Yonezawa, Yamagata, Japan, 2 , Optoelectronic Industry and Technology Development Association, Bunkyo-ku, Tokyo, Japan
Show AbstractWide-energy-gap charge tarnasport materials are required to build high efficiency OLEDs using phosphorescent materials as the emitting center. In this work, we synthesized electron transport materials containing a trimesityl borane structure with high triplet energy level of over 2.7 eV. Also, wide-energy-gap hole transporting arylamine materials and carbazole host materials were synthesized. White OLEDs having a structure of ITO / p-doped hole injection layer / NPD / wide-energy gap arylamine / FIrpic-doped carbazole derivative/ PQ2Iracac-doped carbazole derivative/ FIrpic-doped carbazole derivative/trimesityl borane compound / LiF / Al were fabricated. A high luminous efficiency of 36 lm/W and an external quantum efficiency (EQE) of 18 percent were observed at 100 cd/m2. These values are the highest so far reported for white OLEDs. With an out-coupling optical film attached on the glass surface, a luminous efficiency of 57 lm/W and EQE of 28 percent was observed.
4:00 PM - L3.5
Dual Enhancing Properties of LiF with Varying Positions inside Organic Light-Emitting Devices
Kyul Han 1 , Kyongjin Park 1 , Sang Woo Lee 1 , Kwangho Jeong 1
1 Institute of Physics and Applied Physics and Atomic-scale Surface Science Research Center, Yonsei University , Seoul Korea (the Republic of)
Show AbstractA multilayer organic light-emitting device (OLED) has been fabricated with a thin (0.3 nm) lithium fluoride (LiF) layer inserted inside an electron transport layer (ETL), aluminum tris(8-hydroxyquinoline) (Alq3). The Al (100.0 nm) / Alq3 (50.0 nm) / alpha-N,N’-Bis(naphthalene-1-yl)-N,N’-bis(phenyl)benzidine (α-NPB) (50.0 nm) / indium-tin-oxide (ITO) (70.0 nm) device with the LiF layer inside Alq3 at one forth, half or three forth position assures two different enhancing properties of LiF. When the LiF layer is positioned closer to the Al cathode, the electron injection enhancement is achieved. On the other hand, when the position is away from the Al cathode, the modulation of the electron-hole recombination is achieved inside Alq3. We propose some mechanisms for the dual enhancing properties that the electron injection enhancement is due to the strong LiF diffusion inside Alq3 reaching the Al cathode to form an Al / LiF / Alq3 cathode or the existence of an interface dipole at Alq3 / LiF / Alq3 interfaces to induce a tunneling. The modulation enhancement is due to the insulating nature of stable LiF either modulating the excess holes or the exciton diffusions inside Alq3.
L4: Organic Light Emitting Diodes II
Session Chairs
Tuesday PM, April 18, 2006
Room 3003 (Moscone West)
4:15 PM - L4.1
Investigation of ITO Surface Treatment for the Long-lifetime Organic LEDs
Nobuhiro Ide 2 , Tatsuya Fukushima 1 , Junji Kido 1 2
2 , Optoelectronic Industry and Technology Development Association, Bunkyo-ku, Tokyo, Japan, 1 Polymer Science and Engineering, Yamagata University, Yonezawa, Yamagata, Japan
Show AbstractThe influence of the treatments of indium-tin-oxide (ITO) on the performance of organic LEDs was investigated. The surface properties of ITO were measured by optical and other methods. The morphology and electrical properties of thin organic films deposited on ITO were analyzed by scanning probe microscopy. The interaction, such as the formation of charge-transfer complexes, between the surface treated ITO and organic materials at the interface was observed. It may play an important role to realize the stable interface and, as a consequence, the long-lifetime organic electroluminescent devices.
4:30 PM - **L4.2
Advanced AM-OLED Display Based on White OLED with "Super Top Emission."
Yasunori Kijima 1 , Mitsuhiro Kashiwabara 1 , Shoji Terada 1 , Jiro Yamada 1 , Tatsuya Sasaoka 1 , Tetsuo Urebe 1
1 Display Device Development Group, Sony Corporation, Kanagawa Japan
Show AbstractMany companies have already started mass-production of OLED panels for small size displays. In 2004, Sony commercialized the world largest full-color OLED display for Clie TM PDA. We previously reported top emitting OLED displays [1] [2] employing microcavity structure [3]. The microcavity effect promises high external quantum efficiency and good color coordinates in CIE chromaticity, which are almost equal to NTSC standard. Our top emitting microcavity structure named "Super Top Emission" is an excellent device composition to realize the next generation OLED flat panel display.Our objective is attaining not only the mass-production of the small size OLED, but also the mass-production of the middle or large size OLED display. To achieve this goal, we take advantage of the unique properties of "Super Top Emission" structure, such as large aperture ratio, easy color tuning of RGB emission, high efficiency and high contrast ratio.Sony reported the world’s first 13-inch full-color active matrix OLED display in SID 2001 international symposium [1]. For this panel, we used shadow mask patterning processes to place RGB OLED pixels. As the result, we succeeded in demonstrating OLED’s potential of high quality expression. But the shadow mask patterning of organic layers may bring about pixel defects because of mask distortion or mechanical damage on the TFT back-plane. White OLED (WOLED) and color filter (CF) system has been chosen as one of the solutions to overcome the problems of the mask patterning process. It has been reported as an easy way to obtain large and high resolution panels, but the color coordinates were not as good as those of conventional mask patterned panels.We developed new panel system, WOLED+CF+"Super Top Emission" OLED display on a 12.5inch poly-Si TFT substrate. The microcavity effect contributes to higher color reproducibility, and at the same time, it enables the display to be 1.6 times brighter than the WOLED+CF display. A new red emitting material we synthesized was also used in this panel. This material provids good color coordinates in CIE chromaticity and long operation lifetime, (0.65, 0.35) and over 60,000 hours at the initial luminance of 500 cd/m2 respectively.We consider the WOLED+CF+"Super Top Emission" OLED system is a viable solution to high quality mass-production for the next generation middle or large size OLED display. References [1] T. Sasaoka, M. Sekiya, A. Yumoto, J. Yamada, T. Hirano, Y. Iwase, T. Yamada, T. Ishibashi, T. Mori, M. Asano, S. Tamura and T. Urabe, Proceedings of SID 2001, p384 (San Jose California, June 2001) [2] S. Terada, G. Izumi, Y. Sato, M. Takahashi, M. Tada, K. Kawase, K. Shimotoku, H. Tamashiro, N. Ozawa, T. Shibasaki, C. Sato, T. Nakadaira, Y. Iwase, T. Sasaoka and T. Urabe, Proceedings of SID 2003, p1463 (Baltimore Maryland, May 2003) [3] J. Yamada, T. Hirano, Y. Iwase and T. Sasaoka, AM-LCD 02 Digest, 77-80 (Tokyo Japan, July 2002)
5:00 PM - **L4.3
LITI technology for high-resolution organic LEDs.
Sergey Lamansky 1 , Martin Wolk 1 , John Baetzold 1 , John Staral 1 , Thomas Hoffend 1 , Yingbo Li 1 , Barbara DeBaun 1 , Ha Le 1 , Leslie Kreilich 1 , Kim Goodier 1 , Khanh Huynh 1 , Kenneth Looney 1 , Angela Giese 1 , James Nelson 1 , Andrew Hightower 1 , William Tolbert 1
1 Display and Graphics Business Laboratory, 3M Company, St. Paul, Minnesota, United States
Show Abstract5:30 PM - L4.4
OLED based on Highly Transparent, Conductive and Flexible SWNT Films.
Koungmin Ryu 1 , Daihua Zhang 1 , Xiaolei Liu 1 , Chongwu Zhou 1
1 Electro-Physics, University of Southern California, LA, California, United States
Show AbstractHighly transparent, conductive and flexible films of single-walled carbon nanotube (SWNT) were fabricated by both vacuum filtration and drop casting methods. By optimizing the preparation process we have achieved a very low sheet resistance of 300 Ωper square at a film transparency of 80%, which is comparable to that of commercial ITO thin films. We further demonstrated that the sheet resistance of as-prepared SWNT papers can be reduced by up to one order of magnitude by spin coating a thin layer of PEDOT on the nanotube surface, which also helps improve the surface quality of the SWNT paper without affecting its transmittance. We have also demonstrated a multi-pixel Organic Light Emitting Diodes (OLED) chip using transparent SWNT films as hole-injection electrodes. A device yield of 90% was achieved.
5:45 PM - L4.5
Plexcore™ HIL: Accelerating Commercialization of Organic Light Emitting Diodes.
Darin Laird 1 , Troy Hammond 1 , Shawn Williams 1 , Mathew Mathai 1
1 , Plextronics, Pittsburgh, Pennsylvania, United States
Show AbstractTuesday, April 18New PresenterPlexcore™ HIL: Accelerating Commercialization of Organic Light Emitting Diodes. Mathew Mathai.
L5: Poster Session: Materials for Next Generation Display Systems
Session Chairs
Wednesday AM, April 19, 2006
Salons 8-15 (Marriott)
9:00 PM - L5.1
Optimum Annealing Temperature for BaTiO3 Thin Films Grown on Si Substrates by RF-Magnetron Sputtering.
Ki deuk Min 1 , Dongjin Kim 1 , Kuyjoon Sung 1 , Jongwon Lee 1 , Inyong Park 1
1 Materials Engineering, Department of Materials Engineering, Hanbat National University, Dukmyung-dong, Yuseong-gu, Daejeon, Korea 305-719, Daejon Korea (the Republic of)
Show AbstractBaTiO3 is the typical ferroelectric material with Perovskite structure, and it has excellent electrical and optical properties. It has thus been extensively applied to the fabrication of dielectric materials for nonvolatile memory, capacitor, and display devices. However, there have been very limited number of investigations on the crystallization of BaTiO3 thin films grown on the Si substrate, widely used in the semiconductor processing nowadays. In this study, BaTiO3 thin films were grown on the Si substrate by RF-magnetron sputtering, and the influences of annealing temperature on the crystal quality, surface roughness, phonon frequency, and stoichiometric composition of the films were systematically examined. The optimized growth conditions were 300°C (growth temperature), 10 mtorr (working pressure), 100 W (RF power). The range of annealing temperature was determined to be 500∼1000°C. The XRD results showed that the crystal quality of the BaTiO3 thin films was the best when the annealing temperature was 700 °C. In addition, the Raman spectra demonstrated that the phonon peaks at 288 cm-1 and 520 cm-1 were the most definite with the annealing temperature of 700 °C, showing the excellent crystallization of BaTiO3 films with that annealing temperature. It was found from the FE-SEM results that the grains were formed when the annealing temperature was higher than 700 °C. The XPS measurements were performed to investigate the composition of BaTiO3 thin films and the binding energies of Ba, Ti, and O. The binding energy of Ti2p2/3 were 458.8 eV and 455.5 eV when the annealing temperatures were 700 °C and 1000 °C, respectively, illustrating the phase change into the Ti-rich phase from the stoichiometric BaTiO3 phase with the increase of annealing temperature. The GDS results also showed that the best annealing temperature for the effective crystallization of BaTiO3 layers on Si substrates is 700 °C.
9:00 PM - L5.10
Effect of Oxygen and Hydrogen Gas Ratio on Electrical Properties of ZnO film Deposited by Oxygen Ion-assisted Pulsed Filtered Vacuum Arc.
Sunghun Lee 1 2 , Do-Geun Kim 1 , Eungsun Byon 1 , Minoru Isshiki 2
1 Surface Technology Research Center, KIMM (Korea Institute of Machinery & Materials), Changwon, Gyeongnam, Korea (the Republic of), 2 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai Japan
Show Abstract9:00 PM - L5.11
Effect of Rapid Thermal Annealing on Electrical and Optical Properties of Ga doped ZnO Thin Films Prepared at Room Temperature.
Jong Hoon Kim 1 , Byung Du Ahn 1 , Kyung Ah Jeon 1 , Hong Seong Kang 1 , Sang Yeol Lee 1
1 , Yonsei University , Seoul Korea (the Republic of)
Show AbstractGa doped ZnO (GZO) thin films were prepared by pulsed laser deposition (PLD) on glass substrate at room temperature. Structural, optical, and electrical properties of these films were analyzed in order to investigate their dependence on oxygen pressure, and rapid thermal annealing (RTA). High quality GZO films with a low resistivity of 3.3×10-4 Ωcm and a transparency above 90 % was able to be formed at an oxygen pressure of 3×10-2 Torr and an RTA temperature of 400°C. A four point probe method, X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-NIR grating spectrometer are used to investigate the properties of GZO films.
9:00 PM - L5.12
Transparent ZnO Thin Film Transistors and Their Electrical and Optical Properties.
Jong Hoon Kim 1 , Byung Du Ahn 1 , Kyung Ah Jeon 1 , Hong Seong Kang 1 , Sang Yeol Lee 1
1 , Yonsei University , Seoul Korea (the Republic of)
Show AbstractTransparent ZnO thin film transistors (TFTs) are fabricated on the glass substrates. The devices consist of a high mobility intrinsic ZnO as a semiconductor active channel, Ga doped ZnO (GZO) as an electrode, HfO2 as a gate insulator. GZO and HfO2 layers are prepared by using a pulsed laser deposition and intrinsic ZnO layers are fabricated by using an rf-magnetron sputtering, respectively. High optical transmittance (> 80 %) in visible region and low temperature processing makes transparent ZnO TFTs for heat sensitive substrates.
9:00 PM - L5.13
Effects Of Laser Annealing On Electronic Properties Of Zno:P Thin Films.
Hyun Woo Chang 1 , Hong Seong Kang 1 , Gun Hee Kim 1 , Sung Hoon Lim 1 , Sang Yeol Lee 1
1 Electronical Electronic Enginnering, Yonsei Univ., Seoul Korea (the Republic of)
Show AbstractPhosphorus doped ZnO thin films on (001) Al2O3 substrate have been prepared by a pulsed laser deposition (PLD) using a Nd:YAG laser. Phosphorus doped ZnO thin films deposited by PLD have been annealed in vacuum, air, nitrogen, and oxygen ambients using pulsed Nd:YAG laser. And phosphorus doped ZnO thin films have been annealed by changing laser fluence using pulsed Nd:YAG laser. We report the electrical properties of phosphorus doped ZnO thin films with the variation of the laser annealing conditions for the applications of optoelectronic devices.
9:00 PM - L5.14
Application of HfO2-based Inorganic Dielectric Material for Organic Field Effect Transistor.
Sunwoo Lee 1 , Sang Seol Lee 1 , Taeho Lee 1 , In Sung Park 2 , Jinho Ahn 1
1 Division of Advanced Materials Science and Engineering, Hanyang University, Seoul Korea (the Republic of), 2 Information Display Research Institute, Hanyang University, Seoul Korea (the Republic of)
Show AbstractWith the rapid growth of multimedia device, organic semiconductor device has a strong potential for display applications such as active matrix organic light emitting diodes (AMOLEDs) and liquid crystal display (AMLCD) due to large area coverage, low cost, flexibility, and low process temperature. Especially, among the application of organic semiconductors, p-type single molecular pentacene collects a lot of interests as π-conjugated organic materials because of good performance compared with electron mobility of hydrogentated amorphous Silicon (a-Si:H). When high-k inorganic material is used as a gate dielectric, the operation voltage can be lowered because leakage current can be significantly reduced by high-k dielectric material in organic TFT device. However, the mobility is not high enough to meet requirements on accelerated response time of panel. In this presentation, the OTFT characteristics with pentacene on inorganic HfO2 dielectric film, organic–inorganic stack (OTS/HfO2) structure, and inorganic-organic stack (HfO2/PVP) structure to improve the mobility will be discussed.
9:00 PM - L5.15
Effect of Fabrication Process on Properties of Hole-Injecting Fluorene Oligomer
Junji Kido 1 2 , Tatsuya Fukushima 1 , Jiro Asaka 1 , Nobuhiro Ide 2
1 Polymer Science and Engineering, Yamagata University, Yonezawa, Yamagata, Japan, 2 , Optoelectronic Industry and Technology Development Association, Bunkyo-ku, Tokyo, Japan
Show AbstractThe electrical properties of vacuum deposited and spin-coated hole-transporting fluorene oligomer were investigated. The initial growth of vacuum deposited and spin-coated films were analyzed by using the scanning probe microscope. A non-continuous layer consisted of aggregations of organic molecules was observed for the vacuum deposited film, while a continuous layer completely covering the substrate surface of a substrate was observed for the spin-coated film. Such difference may lead to the the difference in the carrier injection properties. The higher carrier mobility of the vacuum deposited film is attributed to the higher density of the film.
9:00 PM - L5.16
Molecularly Doped Polymers as a Hole Transport Layer in Organic LEDs
Junji Kido 1 2 , Satoshi Ohara 1 , Nobuhiro Ide 2
1 Polymer Science and Engineering, Yamagata University, Yonezawa, Yamagata, Japan, 2 , Optoelectronic Industry and Technology Development Association, Bunkyo-ku, Tokyo, Japan
Show AbstractOrganic LEDs were fabricated using bisphenol-A polycarbonate (PC) molecularly doped with N,N'-diphenyl-N,N'-bis(1-naphthyl-(1,1'-biphenyl)-4,4'-diamine(NPD) as the hole transport layer, tris-(8-quinolinolato) alminium complex (Alq) as the electron transporting emitting layer, and lithium mono(8-quinolinolato) (Liq) as the electron injection layer, respectively. A device structure of glass substrate / indium-tin-oxide / molecularly doped polymer / Alq / Liq / Al was employed. Maximum current efficiency was observed in 40 to 60 wt percent NPD, which is due to the balanced carrier injection, confirmed by the hole mobility mesurement using the Time-of-Flight method.
9:00 PM - L5.17
Synthesis of Printable Perylene-Containing Fluorene Oligomer and Its Application to Organic LEDs
Junji Kido 1 , Makoto Higashidate 1 , Takao Motoyama 1 , Jiro Asaka 1 , Takayuki Ito 1
1 Polymer Science and Engineering, Yamagata University, Yonezawa, Yamagata, Japan
Show AbstractFluorene oligomer containing amino perylene (DFPRA) was prepared and used as an emitting material in organic LEDs. Thin films of DFPRA can be fabricated by vacuum deposition as well as spin-coating. A typical device structure is an ITO / PEDOT:PSS / DFPRA / BAlq / LiF / Al. The device showed yellow emission from DFPRA and the luminous efficiency of 1.0 lm/W. By dispersing DFPRA into an appropriate host material, the device exhibited a high luminous efficiency of over 15 lm/W and an external efficiency of 5 percent.
9:00 PM - L5.18
Investigation of Hydrogen Incorporation and Reactive Ion Etch Process in Silicon Nitride Thin Films at Varying Deposition Parameters.
Saydulla Persheyev 1 , Kevin O'Neill 1 , Mervyn Rose 1
1 Electronics Engineering and Physics, University of Dundee, Dundee United Kingdom
Show Abstract9:00 PM - L5.19
Field Emission from Nanocomposite Carbon Films: Temporal Stability and Effects of Surface Treatments
Adolfo Gonzalez-Berrios 1 , Fabrice Piazza 1 , Gerardo Morell 2 1 , Brad Weiner 3
1 Department of Physics, University of Puerto Rico, Rio Piedras, Puerto Rico, United States, 2 Department of Physical Sicences, University of Puerto Rico, Rio Piedras, Puerto Rico, United States, 3 Department of Chemistry, University of Puerto Rico, Rio Piedras, Puerto Rico, United States
Show Abstract9:00 PM - L5.2
Effect of Hydrogen Gas Addition on Properties of ITO Films Deposited by RF Magnetron Sputtering Method.
Do-Geun Kim 1 , Sunghun Lee 1 , Mirang Park 1 , Gun-Hwan Lee 1
1 Surface Technology Research Center, KIMM (Korea Institute of Machinery & Materials), Changwon, Gyeongnam, Korea (the Republic of)
Show AbstractTin doped indium oxide (ITO) films were deposited on various substrates such as glass, silicon wafer and plastic films by RF magnetron sputtering method using an In2O3 – 10% SnO2 target. The effect of hydrogen gas ratio [H2/(H2+Ar)] on the electrical, optical and mechanical properties were investigated. With increasing hydrogen gas addition, the resistivity of the samples shows the lowest value of 3.5 x 10-4 Ω cm at 0.8% of hydrogen gas ratio, while the resistivity increase over than 1.5% of hydrogen gas ratio. Hall effect measurements explain that carrier concentration and its mobility are strongly related with the resistivity of ITO films. The hydrogen gas addition also reduces the residual stress of the samples up to the stress level of 70Mpa. The surface roughness and the crystallinity of the samples were investigated by using AFM and XRD, respectively.
9:00 PM - L5.20
Relationship between Microstructure Evolution and Electrical Resistivity Variation of Inkjet-printed Ag Films.
Young-hoo Kim 1 , Soo-Jung Hwang 1 , Young-Chang Joo 1
1 School of Material Science & Engineering , Seoul National University, Seoul Korea (the Republic of)
Show AbstractInkjet printing technology has been explored for fabrication of the electronic circuits on the glass or the flexible (polymer or organic) substrates. Since this new display technology has many advantages including low process temperature and no need of any etching process, it is expected that one can fabricate devices faster with significantly less cost using inkjet printing than using the conventional vacuum deposition approaches. Silver (Ag), the most conductive metal, has been studied intensively for inkjet printing. However, because the suspensions for Ag inkjet do not have Ag nanoparticles but also contain organic additives, inkjet-printed Ag films may show the characteristic microstructure evolution behavior, which may have lead to higher resistivity of the corresponding circuits on the devices. We observed the microstructure evolution of the inkjet-printed Ag thin films on polyimide substrates under various annealing conditions using the field-emission scanning electron microscopy (FE-SEM). The microstructure evolution of the inkjet-printed Ag thin films was characterized as occurring in two steps, i.e. densification with pore elimination and the following growth of the Ag grains. Decrease in the resistivity at the initial densification stages is larger than later grain growth stage is measured. In addition, the resistivity values of the inkjet-printed Ag film were calculated using our model in which two mechanisms responsible for electron scattering were taken into consideration. Inkjet printed films have numerous non-conducting pores as well as grains of which sizes are much smaller than those of CVD-deposited films with the same thicknesses. Our model took the grain boundaries and the pores as the major scattering sites. Calculated resistivity values from our model based on the microstructure information from FE-SEM micrographs is compared to those measured using a 4-point probe. The calculated these values agree well with the measured ones.
9:00 PM - L5.21
Cathodoluminescence and Electroluminescence from Multi-layered Organic Structures Induced by Field Electron Emission from Carbon Nanotubes.
Raquel Ovalle Robles 1 2 , Alexander Kuznetov 1 2 , Zakhidov Alexander 3 , Christopher Williams 1 2 , Mei Zhang 2 , Sergey Lee 2 , Jhon Ferraris 2 , Anvar Zakhidov 1 2
1 Physics, University of Texas at Dallas (UT-D), Richardson, Texas, United States, 2 NanoTech, University of Texas at Dallas (UT-D), Richardson, Texas, United States, 3 Physics, Moscow State University, Moscow Russian Federation
Show AbstractWe report the observation of Cathodoluminescence (CL) from organic multilayers of tris-(8-hydroxyquinoline) aluminum (Alq3) and 2-(4biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD) deposited on ITO-coated glass, with and without hole transport layer and compare it with electroluminescence (EL) from similar devices. Excitation of the CL of such multilayer organic anodes was induced by a flow of low energy electrons which are field-emitted in vacuum by single walled and multiwall carbon nanotubes cold cathodes. The dependence of CL spectrum and intensity on a voltage (V), electron current density (I), type of transport layer and the cathode-anode geometry has been studied. We propose carbon nanotubes as an effective transparent cathode for stable CL emission from multi-layer anodes at small cathode-anode separations. The role of hole-transport layer is also discussed.
9:00 PM - L5.22
Field Emission of Electrons from Transparent Carbon Nanotube Sheets.
Alexander Kuznetsov 1 , Alexander Zakhidov 2 , Mei Zhang 1 , Shaoli Fang 1 , Sergey Lee 1 , Ray Baughman 1 , Anvar Zakhidov 1
1 Nanotech. Institute, University of Texas at Dallas, Richardson, Texas, United States, 2 Physics, Moscow State University, Moscow Russian Federation
Show AbstractThe well-ordered aligned arrays of multiwalled carbon nanotubes were used to make strong and transparent carbon nanotube sheets, prepared by dry spinning from oriented MWCNT forrests [1]. Study of electron field emission (FE) shows phenomenally low threshold fields < 0.5 V/mm with very high current densities and steep I-V curves. CNT sheets FE show rather bright and uniform light emission, if CNT sheet is densified on the substrate, so that adhession is increased. They are also rather stable and can even show the self-improvement of current and lowering of a threshold voltage after cycling. Such CNT transparentr sheets can be used as high current, high stability field emission sources which are at the same time transparent and can be used as an optical polarizer. The prototype of high luminosity fluorescent lamp with CNT sheets as a cathode was created.[1] M. Zhang, S.Fang, A.Zakhidov, S.B.Lee, A.Aliev et.al., Science, 309,(2005) 1215
9:00 PM - L5.23
Patterning of Poly(3, 4-ethylenedioxythiophene)(PEDOT) thin films by using self-assembled monolayers(SAMs) patterns formed by ultra-Violet(UV) lithography
Taewook Kwon 1 , Jinyeol Kim 1 , Myungmo Sung 2 , Jaegab Lee 1
1 School of Advanced Materials Eng., Kookmin Univ., Seoul Korea (the Republic of), 2 Department of Chemistry, Kookmin Univ. , Seoul Korea (the Republic of)
Show Abstract9:00 PM - L5.24
The Performance of Cu/Co Gate Electrode Formed Using Selective Deposition of Cu/Co Multilaters on Patterned SAMs for a-Si TFTs.
Jeonggil Lee 1 , Jaegab Lee 1 , Changoh Jeong 2 , Jehun Lee 2 , Yangho Bae 2
1 School of Advanced Materials Eng., Kookmin Univ., Seoul Korea (the Republic of), 2 Active Matrix Liquid Crystal Display Division, R&D team, Samsung Electronics Co., Ltd., Yongin Korea (the Republic of)
Show AbstractMicro contact printing with SAMs was used to pattern and direct the selective CVD(chemical vapor deposition) of cobalt using Co2(CO)8 as a precursor on SAMs patterned glass. After that, subsequently Cu was selectively deposited using (hfac)Cu(3,3-DMB) as a precursor with no vacuum break. MOCVD Co shows excellent selectivity over OTS at the low temperature regime, in which the growth of Co films is surface limited with an activation energy of 0.8 eV. The Co underlayer can act as a promotion layer for Cu nucleation, possibly due to the negligible lattice mismatch of between fcc-Cu(111) and hcp-Co (002) and thus improving the selectivity of Cu over on SAMs coated surface and also enhancing surface roughness. In addition, the Co underlayer provides a glue layer for Cu deposition and thus significantly improves the adhesion property. Finally, the TFT has been fabricated using the Cu/Co multilayers as gate electrode and electrically characterized. A hydrogenated amorphous silicon TFT with a Cu/Co gate electrode exhibited a subthreshold slope of 0.9V/dec, and mobility of 0.38cm2/V-s, on/off current ratio of 107, and a threshold voltage of 0.95V, and thus demonstrating the successful application of the novel bottom-up approach into the fabrication of a-Si:H TFTs. It can be concluded that the newly developed process is suitable for a-Si TFT fabrication, and thus replacing the conventional process.
9:00 PM - L5.25
Synthesis Of Zinc Sulfide Powder By Surfactant Assisted Hydrothermal Process
Kiran Jain 1 , Rashmi Rashmi 1
1 Electronic Materials Division, National Physical Laboratory, New Delhi, India, New Delhi India
Show Abstract9:00 PM - L5.26
Effect of Silver Nanoparticles in the Hole Tranporting Layer on the Performance of Organic Light Emitting Diodes.
Chang Seoul 1 , Jin Heon Kim 1 , Joon Ho Lee 1 , Tae Hun Kim 1
1 Advanced Fiber Engineering, Inha University, Incheon Korea (the Republic of)
Show Abstract9:00 PM - L5.27
Mechanical Properties of ITO film on Polymer Treated by Linear Ion Source.
Shih Hsiu Hsiao 1 , Yoshikazu Tanaka 1 , Ide-Ektessabi Ari 1
1 Mechanical Engineering and Science, Kyoto University, Kyoto Japan
Show Abstract9:00 PM - L5.28
The Stabilization of Liquid Crystal Mode on Flexible Substrates using Anisotropic Phase Separation of Liquid Crystal and Polymer Composite
Tae-Hee Lee 1 , Min Young Jin 1 , Min-Soo Shin 1 , Se-Jin Jang 1 , Jae-Hoon Kim 1
1 Department of Electronics and Computer Engineering, Hanyang University, Seoul Korea (the Republic of)
Show AbstractIn recent years, LC devices using plastic film substrates have drawn much attention for use in applications such as smart cards, PDA, and head mount displays because of their lighter weight, thinner packaging, flexibility, and lower manufacturing cost through continuous roll processing than other similar available devices . However, it is clear that plastic substrates can not give a solid mechanical support for the molecular alignment of LCs between them. To overcome these problems, polymer walls and/or networks as supporting structures have been proposed and demonstrated. These structures were fabricated using an anisotropic phase separation method from polymer and LC composite systems by applying patterned electric field or spatially modulated UV intensity. However, these methods require high electric field to initiate the anisotropic phase separation or remain residual polymers in an unexposed region that reduce optical properties and increase the operating voltage of the device. More recently, we proposed pixel-isolated LC (PILC) mode for fabricating a stable LC structure using anisotropic phase separation produced by contraction and surface wetting properties. Since LC molecules are isolated in pixels surrounded by interpixel vertical polymer walls and horizontal polymer films on the upper substrate in the structure, it shows not only good mechanical stability but also almost the same optical behavior with respect to the normal mode without a polymer.In fabrication of PILC, there occur two kinds of anisotropic phase separation. First, by applying UV irradiation through patterned photomask, spatially modulated polymer wall structure can be generated. And next, weak UV exposure can generate 1-dimensional anisotropic phase separation of remaining polymer and LC along the substrate normal direction which is called phase separated composite organic films (PSCOF). In PSCOF structure, although we use same kind of liquid and polymer mixture, the microscopic textures show very different as alignment materials are changed. Hence to obtain good quality of LC alignment, there is requirement on alignment layer material. We investigated the relation between LC alignment and wetting properties of polymers on alignment layer using glass substrates. By observing polarized microscope and scanning electron microscopic images, we could confirm that LC alignment property in PSCOF structure clearly related to surface properties of polymers. And finally we could obtain good quality of stabilized liquid crystal mode using PILC without loss of alignment quality and electrooptic properties on plastic substrates.
9:00 PM - L5.3
Preparation and Properties of Er-doped GaN Films by Radio Frequency Magnetron Sputtering and Post Annealing Technique.
Chun-Guang Zhang 1 , Liu-Fang Bian 1 , Wei De Chen 1
1 , Institute of Semiconductors, chinese Academy of Sciences, Beijing China
Show Abstract Rare-earth (RE) doping of GaN has received much attention recently because of potential applications for electroluminescence in a wide range of wavelengths from the infrared to ultraviolet. For the application of thin film display device, the study of the low cost and large area deposition method is eagerly required for the preparation of GaN film doped with RE ions. Erbium doped gallium nitride (GaN) films were successfully prepared on Al2O3 (0 0 0 1) and Si (1 1 1) substrates by reactive rf magnetron cosputtering of a gallium oxide (Ga2O3) and a metallic erbium target, together with post annealing ammonification procedure. In addition, we have studied the dependences of infrared photoluminescence (PL) properties at 1.54 μm of GaN films doped with erbium (GaN:Er) on annealing temperature, the thickness of the film and the kinds of substrates. Below 1000 C, the film crystallization and PL peak intensity from GaN:Er/Al2O3 (0 0 0 1) films increased with annealing temperature. Increasing the film thickness could help to strengthen the PL intensity. It is also found that the integrated PL peak intensity from GaN:Er/Al2O3 (0 0 0 1) films was about five times stronger than that from GaN:Er /Si (1 1 1).
9:00 PM - L5.4
Photo Induced Meso-Porous As Low Dielectric Material.
Song Lin 1 2 , Yu Lee 1 , Chu Chen 1
1 Chemical Engineering, National Tsing Hua University, Hsinchu Taiwan, 2 Materials Research Laboratories, Industrial Technology Research Institute, Chutung, Hsinchu Taiwan
Show AbstractPolymer matrix with porous will have lower dielectric constant in general. In this paper, we have applied photochemical reactions to generate meso porous in the photosensitive methacrylate polymer having the tert-butyl carbony side chains. We have exposed Iodonium salt with light at wavelength 365nm to produce strong proton acid. The tert-butyl carbony (t-BOC) side chains of methacrylate copolymer have been broken by proton acid after being heated to 100~120 degree C. Small molecules of isobutene thus produced have been further heated in polymer matrix to generate meso -porous. We note that the exposure dosage and temperature will affect the dimension. Also they have determined the quantity of the porous and the value of the dielectric constant. We have further verified the formation of meso -porous through SEM. The photosensitive material with meso-porous thus produced can be used as a next-generation display systems.
9:00 PM - L5.5
Fluorinated Dimethacrylate Based Copolymer for Liquid Crystal Alignment.
Song Lin 1 2 , Yu Chan 1 , Ya Su 1 , Chein Lee 2 , Yu Lee 1
1 Chemical Engineering, National Tsing Hua University, Hsinchu Taiwan, 2 Materials Research Laboratories, Industrial Technology Research Institute, Chutung Taiwan
Show AbstractWe report a series of non-contact liquid crystal alignment material, which are fluorinated dimethacrylate Copolymer. Surface energy of the alignment material can affect its interaction with the liquid crystal. We have developed a new fluorinated dimethacrylate Copolymer for adjusting polarity and surface interaction with liquid crystal. Therefore, the pretilt angle can be tailored by fluorinated. Moreover, the fluorinated dimethacrylate Copolymer is applicable for polarized UV photo-induced and plasma-treated alignment layer for liquid crystal display. Both synthesis and characterization of fluorinated dimethacrylate copolymer are explored. We have thus successfully controlled the molecular weight of the fluorinated dimethacrylate-based photosensitive polymer with the free radical polymerization. The fluorinated amount of copolymer can be analyzed with solid state NMR. In addition, the surface properties are found related to the contact angle of alignment film and liquid crystal pretilt angle. The excellent alignment uniformity has been achieved by using the polarized UV photo-induced process and the anode layer thruster plasma treatment.
9:00 PM - L5.6
Blue Fluorescent Materials based on Nalidixic Acid Derivatives Coupled with Donor by Non Conjugated Bridge.
Tae-Hyuk Kwon 1 , Kyung-Sik Lee 1 , Myoung Ki Kim 1 , Jongchul Kwon 1 , Su-Jin Park 2 , Dae Yeup Shin 2 , Jong-In Hong 1 3
1 Chemistry, Seoul National University, Seoul Korea (the Republic of), 2 Corporate R&D Center, Samsung SDI, Yongin Korea (the Republic of), 3 Center for Molecular Design and Synthesis, KAIST, Daejon Korea (the Republic of)
Show AbstractWe introduce a new system for blue fluorescent materials in OLEDs based on nalidixic acid derivatives coupled with donor materials by a nonconjugated bridge for the purpose of developing highly efficient blue materials. We call it fluorescent Hopant (Flu-Hopant). The UV and PL maximum peak of nalidixic acid derivatives appeared at 364 nm and 450 nm, respectively. Our previous results showed that its PL quantum yield (0.8) is high because of intramolecular electron push and pull structure. For further enhancement of blue material efficiency, a donor molecule is introduced to the nalidixic acid derivative by a nonconjugated bridge. The mCP, which has already been known as host materials in phosphorescent OLEDs, was used as a donor (maximum emission at 345 nm). Good spectral ovelap between the donor emission and acceptor absorption leads to the singlet-singlet energy transfer through intramolecular bridge bond. Therefore, this Flu-Hopant system is expected to increase the efficiency via intramolecular energy transfer. We compare the photophysical properties of Flu-Hopant with only dopant molecule and dopant-host blending system. The Flu-Hopant system exhibits high energy transfer efficiency in dilute solution. EL device study will also be presented.
9:00 PM - L5.7
Zinc Indium Oxide Based Thin-film Transistors using Organic Gate Dielectric for Transparent Electronics
Yong Hoon Kim 1 , Jeong-In Han 1
1 , Korea Electronics Technology Institute, Seongnam, Kyunggi, Korea (the Republic of)
Show AbstractTransparent oxide based thin-film transistors (TFTs) are now widely investigated as a new switching device for transparent electronics including active-matrix displays. The amorphous oxides composed of heavy-metal cations with (n-1)d10ns0 (n≥4) electronic configurations constitute an interesting class of transparent conductors, since they possess relatively high electron mobilities despite their amorphous character. Recently pulse laser deposited amorphous InGaO3(ZnO)5 based TFTs were reported which exhibit field-effect mobility up to 9 cm2/Vs, and other oxide materials such as zinc oxide (ZnO), zinc tin oxide (ZTO) and zinc indium oxide (ZIO) were also employed as the transparent channel layers. The maximum field-effect mobilites obtained with these materials were 2.5, 50 and 55 cm2/Vs, respectively.Here, we investigated transparent ZIO based thin-film transistors using organic gate dielectric layer for transparent electronics. The channel layer was deposited at room temperature by a rf magnetron sputtering system using a ZIO target with Ar/O2 as sputtering gas. The electrical properties of the TFTs varied with the O2 partial pressure when the channel layer deposition was carried out. With a bottom contact type TFT geometry, using Au as the source-drain electrode, the ZIO based TFT showed field-effect mobility up to 0.5 cm2/Vs and on/off ratio more than 105.
9:00 PM - L5.8
A Study of Oxygen Reduction of Tin- or Zinc-doped Indium Oxide (ITO or IZO) Film Induced by Deposition of Silicon Nitride Film in PECVD Process
Byoung-June Kim 1 , Yong-Mo Choi 1 , Kunal Girotra 1 , Sung-Hoon Yang 1 , Shi-Yul Kim 1 , Soon-Kwon Lim 1 , Jun-Hyung Souk 1
1 LCD R&D Center, Samsung Electronics Co. Ltd., Gyeonggido Korea (the Republic of)
Show AbstractTin doped indium oxide (ITO) or zinc doped indium oxide (IZO), which is called transparent conductive oxide (TCO), is widely used in display devices due to its high optical transmittance and electrical conductivity. Especially, ITO or IZO film is used as the common electrode in fringe field switching(FFS) or plane to line switching(PLS) structure, the new designed structure to improve the aperture ratio. In the fabrication process of amorphous silicon based thin film transistor liquid crystal display (TFT-LCD), ITO or IZO films can be easily exposed to hydrogen-containing plasma in the plasma-enhanced chemical vapor deposition (PECVD) system during the deposition of silicon nitride film as the gate insulating layer. It is widely known, however, that this kind of exposure can easily reduce ITO or IZO to its corresponding metallic element such as indium, which produces the degradation of optical transmittance and conductivity. To clarify this important phenomenon, silicon nitride film was deposited onto ITO or IZO films, and the oxygen reduction of ITO or IZO by atomic hydrogen during PECVD process was analyzed. The oxygen reduction during PECVD deposition is mainly induced by decomposed NH3 gas not by the decomposed SiH4 gas. However, the aspect of this phenomenon in case of IZO is different from that in case of ITO, probably due to the different atomic composition of In2O3 in the composite. Consequently, a new gate insulating layer deposition method is suggested to prevent the oxygen reduction into metallic element from TCO film during the deposition.
9:00 PM - L5.9
Degradation Mechanisms of Green Phosphorescent Dye Doped Polymer Light-emitting Diodes.
Cheng-Guo An 1 , Hyung-Dol Park 2 , Won-Ik Jeong 1 , Jae-Wook Kang 2 , Jang-Joo Kim 1 2
1 School of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Center for Organic Light-emitting Diode, Seoul National University, Seoul Korea (the Republic of)
Show Abstract
Symposium Organizers
Fred B. McCormick 3M Company
Junji Kido Yamagata University
John Rogers University of Illinois, Urbana-Champaign
Shizuo Tokito NHK Science & Technical Research Laboratories
L6: Flexible and Transparent Electronics
Session Chairs
Wednesday AM, April 19, 2006
Room 3003 (Moscone West)
9:00 AM - L6.1
Thin Film Buckling Phenomena of Amorphous Si Deposited by Low Temperature PECVD on Flexible Plastic Substrate.
Jong Hyun Seo 1 , Heung Nam Han 2
1 Dep. of Materials Science and Engineering, Hankuk Aviation University, Goyang-City Korea (the Republic of), 2 School of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Show Abstract9:15 AM - L6.2
Thin-Film Transistors on Strained Si/SiGe Nanomembranes Transferred onto Plastic Substrates.
Hao-Chih Yuan 1 , Michelle Roberts 1 , Donald Savage 1 , Zhenqiang Ma 1 , Max Lagally 1
1 , Univ. of Wisconsin-Madison, Madison, Wisconsin, United States
Show Abstract9:30 AM - **L6.3
Inorganic Semiconductor Thin-Film Transistors for Flat Panel Displays
Jerzy Kanicki 1
1 EECS, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractToday among various flat panel displays (FPDs), the dominant product on the market is active-matrix (AM) liquid-crystal displays (LCDs). In AM-LCDs, hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) is used as key pixel electrode-switching element. It is expected that next generation FPDs will be AM organic light-emitting displays (OLEDs). In such display TFTs is used as both switching and current source devices. From our past experience it is clear that for large area high-resolution AM-LCDs the a-Si:H TFT electrical performance, including stability, must be significantly improved. Also the TFTs to be used in AM-OLEDs must have much better electrical properties in comparison with today’s a-Si:H TFTs. Two possible candidates for this future display technology are polycrystalline (or microcrystalline) silicon (poly-Si) TFTs or oxide semiconductors based devices. The electrical properties, including stability, of silicon- and oxide-based TFTs will be addressed during this talk. Finally, the advantages and disadvantages of advanced a-Si:H TFT structures, poly-Si TFTs and oxides-based TFTs will be discussed during this presentation.
10:00 AM - L6.4
Effect of the Thickness on the Electrical Properties of Transparent TFTs Based on Indium Zinc Oxide.
Pedro Barquinha 1 , Rodrigo Martins 1 , Elvira Fortunato 1
1 Materials Science, FCT-UNL, Caparica Portugal
Show Abstract10:15 AM - L6.5
Characterization of Thin Film Transistor Using DC Reactive Magnetron Sputtered ZnO as a Channel Layer.
Chang Jung Kim 1 , Donghun Kang 1 , Ihun Song 1 , Youngsoo Park 1 , Jaecheol Lee 2 , In-Kyeong Yoo 1
1 Nano Device Lab., SAIT, Suwon Korea (the Republic of), 2 Analysis Engineering Center, SAIT, Suwon Korea (the Republic of)
Show Abstract10:30 AM - L6:Flexible
BREAK
L7: Organic and Hybrid TFTs
Session Chairs
Wednesday PM, April 19, 2006
Room 3003 (Moscone West)
11:00 AM - **L7.1
Application of Pentacene Thin Film Transistors to Backplane of Flexible Display Panel.
Chung Kun Song 1 , G.S. Ryu 1 , K.B. Choe 1 , H. Jung 1
1 Electronics Eng., Dong-A University, Busan Korea (the Republic of)
Show Abstract11:30 AM - L7.2
Flexible (ink) jet Printed Backplanes for Displays: Materials Development and Integration.
Ana Claudia Arias 1 , Jurgen Daniel 1 , Fred Endicott 1 , Rene Lujan 1 , Brent Krusor 1
1 Electronic Materials and Devices Laboratory, Palo Alto Research Center, Palo Alto, California, United States
Show AbstractWe are developing processes to fabricate TFT backplanes on flexible substrates using (ink) jet printing as the only patterning method. In order to achieve good performance and keep the low thermal budget required by flexible substrates a combination of organic and inorganic materials is used in the fabrication process. Polymeric semiconductors, metal nanoparticles and low temperature dielectric layers were integrated to form arrays of thin film transistors to be used as drivers of electronic paper. We study the film formation process of metal nanoparticles deposited from solution and discuss issues of line formation, surface energy control and morphology of these materials. We show that silver nanoparticles exhibit conductivities high enough to be used as addressing lines on display backplanes at temperatures as low as 150 °C. The semiconducting polymer films used are polythiophene derivatives, P3HT and PQT-12, and were self-encapsulated by depositing the semiconductor blended with an insulating polymer from solution. The morphology of the phase separated film was controlled so that the insulator material segregates to the top surface encapsulating the underlying semiconductor. Bottom gate TFTs were fabricated with blends of semiconducting and insulating polymers at different concentrations and mobilities as high as 0.05 cm2/Vs were obtained. TFT devices were operated in air and showed stable sub-threshold voltages up to 21 days in air. This self-encapsulating process is compatible with (ink) jet printing and it allowed the fabrication of 180x180 pixels array for display backplanes. The self-encapsulating process also improves the integration of printed TFT backplanes with display media. Finally, we discuss the challenges of integrating low temperature dielectric layers to printed processes. We show that pixel design benefits from the registration accuracy of jet-printing and that the electrical performance is suitable for addressing capacitive media displays.
11:45 AM - L7.3
Nanostructured High-dielectric Polymer Insulators for Organic Thin Film Transistor.
Jihoon Kang 1 , Nayool Shin 1 , Mi Jung Han 3 , Jang-Joo Kim 2 , Do Yoon 1
1 Department of Chemistry, Seoul National University, Seoul Korea (the Republic of), 3 , Samsung Electronics Co., LTD., Yongin Korea (the Republic of), 2 School of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractTo achieve solution processed, all-organic thin film transistors (OTFTs), development of new polymeric gate dielectric materials is essential, which have excellent electrical properties and processibility. At the same time, the dielectric layers have to provide good interface properties with the active layer. It is well known that the electrical properties of organic thin film transistors is mainly determined by the interface characteristics, and many efforts have been devoted to improve the interface properties which include double dielectric layers and monolayer construction of long alkyl chain like octadecyltrichlorosilane (OTS). We synthesized new polymeric gate dielectric materials which have both a high dielectric constant and a low surface energy. The dielectric constant of the synthesized polymer is as high as 11 at 1 MHz, and the water-contact angle is ca. 105°. Top-contact type pentacene organic thin film transistors were fabricated utilizing spin-coated polymeric materials as gate dielectric layer, which gave the field effect hole mobility of 1.8 cm2/Vs and low operating voltage. Moreover, the nanostructure of the polymer dielectric films, and the relationship between the electrical characteristics of OTFT and the property of dielectric layer was also studied.
12:00 PM - L7.4
Atomic Layer Deposition Of ZnS Thin Films For The Oitft (Organic-Inorganic Tft) Channel Layer.
SeoungWoo Kuk 1 , Inhoe Kim 1 , Sangtae Lee 1 , Seokhoon Kim 1 , Hojung Chang 2 , Hyeongtag Jeon 1
1 Division of materials science and engineering, Hanyang University, Seoul Korea (the Republic of), 2 Department of Electronics Engineering, Dankook University, seoul Korea (the Republic of)
Show AbstractZnS thin films were grown by Atomic Layer Deposition (ALD) method with ZnCl2 and hydrogen sulfide precursors in order to fabricate the driving thin-film transistors (TFT) for the next generation display. In this study, the organic thin-film transistors (OTFT) have been mainly investigated to use of TFT for the next generation display, especially flexible display. OTFT has many advantages such as flexible structure, low temperature progress and low cost. However, OTFT is not good for an advanced flat panel display because of its low channel mobility, slow switching speed, and weak thermal stability, etc.For this reason, in this study, we fabricate organic-inorganic thin-film transistors (OITFT) structure in which have inorganic channel layer to improve the channel mobility. We deposited ZnS thin films as a channel layer for an OITFT structure and studied its various properties. We used a traveling wave type ALD system and used various substrates such as 4-inch wafers, bare glasses, and organic layer deposited-glasses. The deposition rate of the ZnS films in our system was about 1.5Å/cycle.We analyzed chemical bonding of ZnS with X-ray photoelectron spectroscopy (XPS). Zn peak and S peak of ZnS thin film appeared in the range of 1022 ~ 1022.5eV and 162 ~ 162.5eV, respectively. Auger Electron Spectroscopy (AES) for chemical analysis and transmission electron microscopy (TEM) for interface morphology were performed for the analysis of those films. Also, we fabricated capacitor and transistor structure with ZnS channel layer. We observed the electrical characteristics of those structures by the C-V, I-V analysis. From these results, we studied possibility of the application from ZnS to channel layer of OITFT for a display field.
12:15 PM - **L7.5
Printed Organic Transistors for Large-area, Flexible Sensors and Actuators.
Takao Someya 1 , Yoshiaki Noguchi 1 , Yusaku Kato 1 , Tsuyoshi Sekitani 1 , Takayasu Sakurai 2
1 Quantum-Phase Electronics Center, University of Tokyo, Tokyo Japan, 2 Center for Collaborative Research, University of Tokyo, Tokyo Japan
Show AbstractWe report recent progress and future prospects of large-area, flexible sensors and actuators using organic field-effect transistors (FETs). Those new classes of applications include a sheet image scanner, an artificial electronic skin, and a sheet Braille display. Particularly, we describe technical details of large-area, flexible pressure sensors with organic FET active matrixes manufactured on plastic films using printing techniques, namely, inkjet and screen-printing machines. First, we describe an inkjet printing process of heat-resistant polyimide for gate dielectric layers and that of silver nano particles for metal electrodes. To form gate electrodes and word lines, silver nano-particles are patterned on poly(ethylenenaphthalate) (PEN) or polyimide films by an inkjet printer (IJP-1, Ricoh Printing Systems) with a stainless steal inkjet head (GEN3E1), which is driven by multilayered piezoelectricity and equipped with 96 linear array nozzles. A high-purity polyimide precursor (Kemitite CT4112, Kyocera Chemical) is patterned by the same inkjet machine with the similar head. A solution containing polyimide precursors is diluted by N-Methyl-2-pyrrolidone (NMP) to adjust viscosity. The surface of the inkjet-patterned polyimide layer was characterized by AFM. Its smoothness is comparable to that of spin coating (RMS=0.2 nm). Compared with spin coating, the present inkjet printing of polyimide is compatible with a roll-to-roll process and does not require additional patterning process for via interconnection, thus it is potentially ultra low in manufacturing cost. Although the present precursor-type polyimide was dissolved in an NMP-based solution harm to bonding segment, we have demonstrated that the newly developed inkjet head, which is assembled with minimum use of bonding segment, can realize inkjet patterning of high-quality precursor-type polyimide suitable for organic FETs. In order to demonstrate feasibility of printed polyimide for organic FET applications, a 50-nm-thick pentacene was deposited by thermal evaporation on the films with inkjet-printed polyimide gate dielectric layer. The mobility was 0.7 cm2/Vs in the saturation regime and the on/off current ratio was above 106. Employing inkjet-printed polyimide, we have manufactured organic matrix active matrixes on plastic films and laminated those films with organic pressure-sensitive rubber in order to realize large-area, flexible pressure sensors. The effective sensing area is 46 × 46 cm2 and the total number of pressure sensor cells is 90 × 90. This study is partially supported by CREST, JST, IT Program, MEXT, MPHPT, TOKUTEI (15073204), and NEDO.
L8/M5: Joint Session: Organic Field Effect Transistors I
Session Chairs
Wednesday PM, April 19, 2006
Room 3001 (Moscone West)
2:30 PM - **L8.1/M5.1
Vapor and Solution Deposited Organic Thin Film Transistors
Tom Jackson 1
1 Department of Electrical Engineering, Center for Thin Film Devices and Materials Research Institute, Penn State University, University Park, Pennsylvania, United States
Show AbstractThe history of the microelectronics industry over the past four decades or more has been largely an elaboration of Moore’s Law, but many future electronic opportunities will be in non-Moore’s law applications. Organic thin film electronics is well suited to non-Moore’s-law electronics applications because of the diversity and flexibility of the devices, function, and processing it allows. Organic thin film transistors (OTFTs) are particularly interesting because they can act as enabling devices to allow the integration of other organic devices in displays, sensor arrays, low cost memories, and other applications in addition to use in standalone OTFT applications.For practical device and system use, OTFTs must demonstrate the uniformity, reproducibility, reliability, and integration with other devices needed for realistic applications. As one possible application, we have considered the integration of vapor-deposited OTFTs with organic light emitting diodes (OLEDs) and have fabricated small test displays that allow us to investigate device characteristics and passivation and isolation requirements for integrating these organic devices.Many organic device applications are likely to be cost sensitive and solution-deposited organic semiconductors may offer important advantages for low-cost processing. However, solution processed semiconductors typically lack the molecular-level order which may be important for good carrier transport and large field-effect transistor mobility. Working with J. Anthony (University of Kentucky) we have investigated functionalized pentacenes and pentacene derivatives. These materials use bulky molecular side groups to control molecular packing and allow solubility in a range of common solvents. Surprisingly, solution-deposited films of some of these materials show good molecular ordering and, using these materials, we have been able to fabricate OTFTs with mobility > 1.5 cm2/V-s.The technological landscape appears ripe for an explosion of organic electronic applications. Details of device structure, function, and performance are critically related to the success of various application possibilities and organic thin film electronic offers unique advantages. The wide range of device and application possibilities as well as physical phenomena makes this one of the most interesting and exciting areas of device physics and engineering with potentially large economic and societal impact.
3:00 PM - L8.2/M5.2
Hot Wall Epitaxially Grown Fullerene Films for High-Mobility Organic Thin-Film Transistors.
Birendra Singh 1 , Nenad Marjanovic 1 , Helmut Neugebauer 1 , Niyazi Sariciftci 1 , Alberto Ramil 2 , Andrei Andreev 3 , Helmut Sitter 2 , Siegfried Bauer 4 , Thomas Anthopoulos 5 , Dago Leew 5
1 Linz Institute of Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University of Linz, Linz Austria, 2 Institute of Semiconductor and Solid State Physics, Johannes Kepler University of Linz, Linz Austria, 3 Institute of Physics, University of Leoben, Leoben Austria, 4 Soft Matter Physics (SOMAP), Johannes Kepler University of Linz, Linz Austria, 5 Philips Research Laboratories, Prof. Holstlaan 4 (WAG11), Eindhoven Netherlands
Show AbstractHot wall epitaxy (HWE) is a well known technique for growing highly ordered thin films of C60 and para-hexaphenyl nano-needles.1 Here we report on HWE grown fullerene based n-channel organic field-effect transistors (OFETs) with electron mobility in the order of 6 cm2/Vs and current on/off ratio >105. Optimisation of these devices includes use of solution-processed high-glass transition temperature organic dielectrics and accurate control of substrate temperature during film growth. To demonstrate the quality of our HWE C60 films we fabricate an unipolar (n-type) seven-stage ring oscillator with oscillating frequency as high as 30 KHz. The HWE technique is also used to grow crystalline nano-needles of para-hexaphenyl on crystalline substrates.1 The average needle length and width are in the order of 30 µm and 100 nm respectively. The anisotropic charge carrier transport of para-hexaphenyl nano-needles based high mobility OFETs and from the measurement of space charge limited current (SCLC) are also presented. 1A. Andreev, G. Matt, C. J. Brabec, H. Sitter, D. Badt, H. Seyringer and N. S. Sariciftci, Adv. Mat. 12, 629 (2000).
3:15 PM - L8.3/M5.3
Optical Effects in Rubrene OFETs and Related Optical Properties of Rubrene Single Crystals.
Vitaly Podzorov 1 , Hikmat Najafov 2 , Matt Calhoun 1 , Ivan Biaggio 2 , Michael Gershenson 1
1 Physics Department, Rutgers University, Piscataway, New Jersey, United States, 2 Physics Department, Lehigh University, Bethlehem, Pennsylvania, United States
Show AbstractOptical absorption, luminescence, and charge carrier photoexcitation mechanisms of rubrene single crystals will be briefly discussed [1], followed by a discussion of novel optical effects observed in rubrene OFETs. Photo-induced charge transfer of positive or negative charges across the interface between the ordered organic crystal and a polymeric insulator is observed in the field-effect experiments [2]. The effect occurs when OFET is illuminated through a semi-transparent gate electrode with photons of energy exceeding the absorption edge of rubrene. The transferred charge is trapped in the insulator, resulting in a shift of the field-effect onset that can be controlled by light intensity and by the sign and magnitude of the gate voltage applied during illumination. 1. H. Najafov, et al. http://arxiv.org/abs/cond-mat/05107682. V. Podzorov and M. E. Gershenson, Phys. Rev. Lett. 95, 016602 (2005);
3:30 PM - **L8.4/M5.4
Solution-Processed Polymer Ferroelectric Field-Effect Transistors.
Paul Blom 1 , Ronald Naber 1 , Gerwin Gelink 2 , Albert Marsman 2 , Dago de Leeuw 2
1 Materials Science Centre, University of Groningen, Groningen Netherlands, 2 , Philips Research Laboratories, Eindhoven Netherlands
Show AbstractWe demonstrate a rewritable, nonvolatile memory device with flexible plastic active layers deposited from solution. The memory device is a ferroelectric field-effect transistor (FeFET) made with a ferroelectric fluoropolymer and a bisalkoxy-substituted poly(p-phenylene vinylene) semiconductor material. The on- and off-state drain currents differ by several orders of magnitude, have a long retention time, a high programming cycle endurance and short programming time. The remanent semiconductor surface charge density in the on-state has a high value of 18 mC/m2, which explains the large on/off ratio. Application of a moderate gate field raises the surface charge to 26 mC/m2, which is of a magnitude that is very difficult to obtain with conventional FETs because they are limited by dielectric breakdown of the gate insulator. In this way, the present ferroelectric/semiconductor interface extends the attainable field-effect band bending in organic semiconductors.Using an ambipolar bulk heterojunction semiconductor the polarity of the ferroelectric FET can be remanently switched from n- to p-type and back. The high charge density of 28 C/m2 induced by the ferroelectric combined with a high mobility in a regioregular polythiophene in a top-gate transistor layout yield a record conductance value of 0.3 μS for conjugated polymer based FETs.
L9/A16: Joint Session: AMOLED Backplanes Electronics
Session Chairs
Wednesday PM, April 19, 2006
Room 3002 (Moscone West)
4:30 PM - **L9.1/A16.1
Backplane Requirements for Active Matrix Organic Light Emitting Diode Displays.
Arokia Nathan 1
1 Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario, Canada
Show AbstractOrganic light emitting diode (OLED) displays are a serious competitor to liquid crystal displays in view of their superior picture quality, higher contrast, faster on/off response, thinner profile, and high power efficiency. While the passive matrix OLED display structure is simple, its pulse-driven nature leads to high power consumption and low lifetime, restricting its use to small, low-resolution displays. For large size and/or high-resolution applications, an active matrix OLED (AMOLED) addressing scheme is vital, requiring use of a thin-film transistor (TFT) pixel circuit to regulate the OLED current. The active matrix backplane can be made with amorphous silicon (a-Si), polysilicon, or organic technology, all of which have significant drain-current degradation due to threshold voltage (VT) shift or mismatch problems, which cause temporal or spatial variations in the OLED brightness. In addition, the efficiency of the OLED itself degrades over time. Despite material weaknesses, considerable progress is being made in designing AMOLED displays with stable and uniform brightness using circuit solutions to compensate for low lifetime and differential aging. Indeed the design of AMOLED pixel circuits, particularly in low-mobility TFT technologies such as a-Si, is challenging due to the stringent requirements of timing, current matching, and low voltage operation. However, circuit solutions, while necessary, are not sufficient, which raises the question of whether process improvements can be made to enhance TFT performance. This paper will review pertinent material requirements of AMOLED backplanes along with design considerations that address pixel architecture, contact resistance, and more importantly, the VT-stability and gate overdrive. In particular, can conventional PECVD be deployed for high mobility and high VT-stability nano-crystalline silicon TFTs, including thin film CMOS for eventual system-on-panel integration?
5:00 PM - L9.2/A16.2
Flexible AMOLED Backplane Based on Excimer Laser Annealed Poly-Si TFT on Metal Foil.
JengPing Lu 1 , Yu Wang 1 , Chinwen Shih 1 , Yunan Pei 1 , Jackson Ho 1 , Robert Street 1 , Keith Tognoni 2 , Bob Anderson 2 , Dave Huffman 2 , Anna Chwang 3 , Richard Hewitt 3 , Ken Urbanik 3 , Michael Hack 3 , Julie Brown 3 , Teresa Ramos 4 , Lorenza Moro 4 , Nicole Rutherford 4
1 , Palo Alto Research Center, Palo Alto , California, United States, 2 , L3 Communications, Alpharetta, Georgia, United States, 3 , Universal Display Corporation, Ewing, New Jersey, United States, 4 , Vitex Systems, San Jose, California, United States
Show AbstractTFT backplanes on flexible substrates have become the current research trend because of the recent surge of interest in flexible displays. Based on our previously developed, conventional Exicmer Laser Annealed poly-Si TFT on glass process, which has shown excellent performance and has been successfully used to implement many demanding applications, such as active pixel flat panel imagers, PARC has developed a poly-Si TFT on thin metal foil technology. By carefully modifying the process steps and conditions, we have successfully demonstrated the TFTs on flexible substrates with similar performance as TFTs on glass such as high mobility (78 cm2/Vs for p-channel), low off-state leakage current (0.1pA/μm), and sharp turn on (S=0.38 V/decade). Targeting the application of driving low power consumption phosphorescent OLED displays, PARC, UDC, Vitex, and L3 have jointly demonstrated a prototype, thin film encapsulated AMOLED display on stainless steel foil with a 100 dpi resolution. In this talk, we will report the current status of the development of poly-Si TFT on thin metal foil. TFT performance, uniformity, stability, as well as pixel circuit will be discussed.
5:15 PM - L9.3/A16.3
a-Si:H 2-TFT AMOLED Pixel Circuits on Stainless Steel Foils.
Alex Kattamis 1 , I-Chun Cheng 1 , Sigurd Wagner 1 , Yongtaek Hong 2
1 Department of Electrical Engineering and The Princeton Institute for the Science and Technology of Materials (PRISM), Princeton University, Princeton, New Jersey, United States, 2 Display Science and Technology Center, Eastman Kodak Company, Rochester, New York, United States
Show Abstract5:30 PM - **L9.4/A16.4
Flexible Substrate All Organic Active Matrix Displays.
Tom Jackson 1
1 Electrical Engineering, Penn State University, University Park, Pennsylvania, United States
Show AbstractThere is great interest in active matrix organic light-emitting diode (AMOLEDs) displays because of their potential for thin, light weight, low-power, and possibly also flexible displays. AMOLED displays have been demonstrated on stainless steel and polymer substrates [1, 2], using poly-silicon or amorphous silicon TFTs as the active elements. Organic thin film transistors (OTFTs) are of interest for pixel control devices because of the possibility of reduced processing temperature and cost.We have fabricated 48 x 48 pixel pentacene OTFT driven AMOLED displays on flexible polyethylene terephthalate (PET) substrates. The displays use a simple two transistor per pixel drive scheme with a pixel pitch of 500 μm and an aperture ratio of 0.52. The drive and select transistors have a W/L ratio of 10 (200 μm/20 μm) and 1 (20 μm/20 μm), respectively, and the storage capacitor is 1.2pF. For display fabrication, 2.5 × 2.5 inch, 125 μm thick PET substrates are laminated to glass plates using a removable pressure-sensitive silicone gel to maintain a flat PET surface. The pentacene OTFTs are patterned using photosensitive polyvinyl alcohol and isolated from the OLEDs by a parylene layer. After display fabrication the PET display substrate is easily removed from the glass carrier. Although the pixel and line defect density is significant in our simple displays, flexible OTFT-AMOLED display function is demonstrated. This indicates that OTFT backplanes are viable candidates for active-matrix OLED flexible displays. 1. Afentakis, T., et al. “Poly-silicon TFT AM-OLED on thin flexible metal substrates,” Poly-Silicon Thin Film Transistor Technology and Applications in Displays and Other Novel Technology Areas. SPIE 5004-30 (2003).2. Nichols, J.A., et al. “a-Si:H TFT phosphorescent OLED active Matrix Pixels fabricated on polymeric substrates,” 2004 Device Research Conference Technical Digest, pp. 59-60 (2004).
Symposium Organizers
Fred B. McCormick 3M Company
Junji Kido Yamagata University
John Rogers University of Illinois, Urbana-Champaign
Shizuo Tokito NHK Science & Technical Research Laboratories
L10: Electrochromic and LCD Systems
Session Chairs
Thursday AM, April 20, 2006
Room 3003 (Moscone West)
11:30 AM - L10.1
Electrochromic Properties of Polycrystalline Nb2O5 Thin Films with Mg2+ Ions.
Gargi Agarwal 1 , G. B. Reddy 1
1 Physics, Indian Institute of technology Delhi, New Delhi, New Delhi, India
Show AbstractElectrochromism refers to the reversible and persistent change in optical properties of a material when ions are inserted and deinserted into/from it with the help of an electric field. The phenomenon of electrochromism is extensively employed to fabricate solar selective devices to control the energy flow through the domestic windows. These are popularly known as smart windows/dynamic windows. The same phenomenon has been extended to variable emittance devices for thermal control in spacecrafts. The basic device structure consists of five different layers. The most important part of this device is the electrochromic layer that exhibits significant changes in the optical properties. Many transition metal oxides namely, WO3, MoO3, V2O5 exhibit this phenomena. Nb2O5 is another promising transition metal oxide which shows this property. Electrochromic studies on Nb2O5 films have so far been carried out with univalent Li+/H+ ions largely. But, due to the hazardous effect of lithium salts and also their high cost, search for an alternative material is underway. Salts of divalent Mg2+ ions have emerged to be a possible substitute to Li salts. Recently there have been reports on successful Mg2+ intercalation in MoO3 films also. So for the first time electrochromic studies have been done on Nb2O5 using divalent Mg2+ ions and the results have been presented in this paper. Nb2O5 thin films have been deposited by the sol-gel dip coating technique using niobium ethoxide [Nb(OC2H5)5] as the molecular precursor. As deposited films on transparent conducting oxide (TCO) are amorphous and got crystallized into hexagonal phase on annealing at 600oC. The crystalline films were intercalated with different concentrations (x) of Mg2+ in the galvanostatic mode using 0.1M Mg(ClO4)2 in propylene carbonate as the electrolyte solution. x is actually the ratio of the Mg2+ ions to the Nb atoms of the host. Optical and structural propertied were measured before and after intercalation keeping the film thickness constant. The transmittance in the 350 – 700 nm spectral region has decreased from 75% to 30% when x = 0.6. The decrease in transmittance is found to depend on x upto x = 0.6. XRD studies revealed formation of MgNb2O6 phase, whose concentration is seen to grow with x value. The deintercalated films show complete withdrawal of the Mg2+ and also the MgNb2O6 phase formed during intercalation also disappeared. The FTIR studies of the intercalated films confirm the presence of Mg-O-Nb bonds, Mg(OH)2 and adsorbed water in these films. The intensity of the IR peaks corresponding to the Mg-O-Nb system varies with x.
11:45 AM - L10.2
Fabrication and Impedance Analysis of Organic Electrochromic Device: From 1×1 inch Lab Demo to 12×20 inch Prototype Window.
Xiangxing Kong 1 , Chunye Xu 1 , Soo Kim 1 , Lu Liu 1 , Minoru Taya 1
1 Mechanical Engeineering, University of Washington, Seattle, Washington, United States
Show Abstract12:00 PM - L10.3
New Liquid Crystal Materials for Bistable Flexible Displays.
John West 1 , Fenghua Li 1 , Chae Il Cheon 2 , Anatoliy Glushchenko 3
1 Liquid Crystal Institute, Kent State University, Kent, Ohio, United States, 2 Dept. of Mat. Sci. & Eng. , Hoseo University, Sechul-ri, Baebang-myun, Asan-si, Chungnam 336-795 Korea (the Republic of), 3 Dept. of Physics, University of Colorado at Colorado Springs, Colorado Springs, Colorado, United States
Show AbstractIn this review we present a new method of modifying the properties of existing liquid crystals by doping them with ferroelectric micro- and nanoparticles. We show that this approach, in contrast to the traditional time consuming and expensive chemical synthetic methods, enriches and enhances the electro-optical performance of many liquid crystal materials. We demonstrate that by changing a concentration and a type of ferroelectric particles one can affect physical properties of the nematic, smectic, and cholesteric liquid crystal materials, including the dielectric constants, the birefringence, the phase transition temperatures, and even the order parameter. We bring a phenomenological model of interaction between the particles and liquid crystals, which explains the observed effects. We also demonstrate the performance of these new materials in various devices, including bistable flexible displays, light modulators, and beam steering devices.Keywords: ferroelectric particles, liquid crystal properties, birefringence, dielectric constants, order parameter, low voltage, high speed, high contrast
12:15 PM - L10.4
Synthesis of Photoreactive Hybrid Materials for Photoalignment of Liquid Crystal
Tae-Ho Lee 1 , Jeong Hwan Kim 1 , Byeong-Soo Bae 1
1 Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon Korea (the Republic of)
Show AbstractThe photo-induced alignment of liquid crystals (LCs) using polarized UV irradiation of polymer film has attracted much attention because this technique can be a promising method in the next generation of liquid crystal displays (LCD). The mechanical rubbing method currently used in LCD panel fabrication caused critical problems such as static charge or dust generation during the process. As photoalignment method can produce surface anisotropy of photoreactive films by noncontact means, it can be an appropriate method for large area, multidomain and in-plane switching mode LCD. However, this noncontact technique of photo-alignment of LCs has not been adopted commercially, due to poor thermal stability. Thus, high photosensitive and thermally, electrochemically, and photochemically stable material should be requried.A wide range of photoreactive materials have been investigated for the photoalignment layer with high thermal stability of LCs orientations. Especially, polymer or oligomer with high photoreactive vinyl cinnamate groups has been intensively studied. For examples, polyimide main chain with cinnamate groups, blends of poly (vinyl cinnamate), poly(methyl methacrylate), polyethylene and polysiloxanes with pendent cinnamate groups were reported. In this study, we will report the photoalignment of LCs using the vinyl cinnamate modified siloxane oligomers (VC oligosiloxanes) as a class of inorganic-organic hybrid materials. VC oligosiloxanes were synthesized by simple sol-gel process and possess many excellent properties such as being colorless and transparent, glasslike film forming ability, high adhesion to glass and silicon substrate and superior solubility in common organic solvents. VC oligosiloxanes were prepared from reaction of amine modified oligosiloxane with cinnamoyl chloride. Homogeneous VC oligosiloxanes thin films were successfully prepared on glass through conventional spin casting and drying process. Also, imide hybrid nanocomposites containing VC groups were fabricated as hybrid materials with higher thermal stability and mechanical strength. The structures of VC oligosiloxanes and imide hybrid nanocomposites containing VC groups were examined by 29Si NMR, FT-IR, Raman, SANS and Mass spectroscopies. Photochemical reaction of cinnamate groups in solution and films were investigated by UV-Vis spectroscopy. The orientation of LCs induced by linear polarized UV exposure was measured using optical setup. Pretilt angle and homogeneity of LC alignment were estimated as a function of UV dose. Photoalignment behaviors depending on rigidity of structure and surface energy were compared in two different hybrid materials. The direction of the LC alignment was perpendicular to the electric vectors of linear polarized UV. Good photoalignment of LCs with high photosensitivity was show in the fabricated films of VC oligosiloxane and imide hybrid nanocomosites containing VC groups, and was stable in high temperature.
L11: FEDs, PDPs and Next Generation Display Materials
Session Chairs
Thursday PM, April 20, 2006
Room 3003 (Moscone West)
2:30 PM - L11.1
Tuning the Cathodoluminescence in Porous Silicon by in-situ surface Hydrogen Bombardment.
Azlin Biaggi-Labiosa 1 , Luis Fonseca 1 , Oscar Resto 1
1 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States
Show AbstractCathodoluminescence (CL) spectra from critical point dried p-type Porous Silicon films excited with low energy electron beams compatible with Field Emission Displays technology were blue shifted by in-situ surface ion-bombardment. Without the ion treatment, the CL emission peaks are above 700nm in wavelength. After ion treatment, the CL emission peaks shift to shorter wavelengths suggesting successful removal of oxygen-related electron trapping states from the surface by the hydrogen ions. The blue shifted CL peaks correlates with band-to-band transitions in the silicon nanoparticles and can be tuned to yellow and green depending on the sample preparation procedure in which smaller particles can be obtained by prolonged etching with extended HF soaking under illumination.
2:45 PM - L11.2
VUV Excitation Spectra properties of PO43--base phosphates doped with Eu3+ or Tb3+
Yuhua Wang 1 , Dan Wang 1
1 , Lanzhou university, Lanzhou China
Show AbstractUltraviolet (UV) excitation spectra of rare earth doped phosphate had been systemically investigated. However, vacuum ultraviolet (VUV) excitation spectra of rare earth doped phosphate were scarcely reported. Through investigating the VUV spectroscope of rare earth doped phosphates in details, we could understand the luminescence mechanism of rare earth ions in the VUV region and get a rule to guide us to design new efficiency fluorescence hosts for plasma display panel (PDP) and Hg free lamps. In this presentation, Eu3+ or Tb3+ doped orthophosphate, double phosphate and metaphosphate were prepared and investigated. In the excitation spectra of Eu3+ doped samples, below 200nm two broad bands were observed for all the samples, one lied at 120-160nm with the maximum at 149nm, the other lied at 160-200nm with the maximum at 180nm. According to the diffuse spectrum of YPO4 measured by E.Nakazawa [1], and considering PO43- anions were the only common composition of all the samples, so the bands below 200nm could be comprised of the absorption of PO43- anions. In the excitation spectra of Tb3+ doped samples, the stronger transition absorption bands of Tb3+ from lower level of 4f8 configuration to the energy levels of 4f75d figuration located at about 170-225nm with the maximum at about 175nm, and the absorption band of PO43- anions at 149nm was observed, the others were overlapped with the transition absorption bands of Tb3+. Because the absorption band of B-O tetrahedron located at about 150nm and the absorption band of Si-O tetrahedron located at about 180nm.The samples which P5+ were substituted by B3+ or Si4+ were prepared and investigated. In the excitation spectra, the absorption bands at 149nm and 180nm were increased when B3+ substituted for P5+ and the absorption band at 180nm was increased only when Si4+ substituted for P5+. These results confirmed the absorption bands at about 149nm and 180nm included the absorption of PO43- anions again and implied the intensity of absorption bands of PO43- anions could be influenced by the composition of the host. In addition, the absorption band of at 230nm was overlapping of the charge transition absorption band of Eu3+ with the maximum at about 225nm. This means the occurrence of the energy transfer efficiency from PO43- anions to Eu3+.
3:00 PM - L11.3
Spin-on Dielectric Materials for Next Generation Display Systems.
Jinghong Chen 1 , Brian Daniels 1 , Pete Smith 1 , Mehari Stifanos 1 , Roger Leung 1 , Jan Nedbal 1 , Amanuel Gebrebrhan 1 , Ahila Krishnamoorthy 1 , Wenya Fan 1 , Emma Brouk 1
1 , Honeywell Electronic Materials, Sunnyvale, California, United States
Show AbstractIn the flat panel display industry, there is a technology shift from CVD to spin-on dielectrics for TFT (thin film transistor) structures due to the needs of cost reduction in large panel manufacture and performance improvement in mobile devices. In this paper, we present recent advances on development of spin-on dielectric materials for two applications: Gate Dielectric (GD) and Planarization Layer (PL) for TFTs. In the Gate Dielectric application, we have synthesized methylsiloxane polymers with noteworthy dielectric properties. At a curing temperature of 250 °C, the dielectric constant is 3.46, the breakdown voltage is 4.11 MV/cm at 1 µA/cm 2, the leakage current is 4.9 x 10 -8 A/cm 2 at 2.5 MV/cm, and the CV hysteresis is 3.4 V. At a curing temperature of 425 °C, the dielectric constant, the breakdown voltage, the leakage current, and the CV hysteresis are 3.2, 4.65 MV/cm, 2.6 x 10 -8 A/cm 2, and 0.44 V respectively at the above mentioned testing conditions. In the Planarization Layer application, we have produced silicate films that have crack thresholds of more than 1 µm by doping silicate sol-gel materials with nanometer-size colloidal silica. Due to the inorganic nature of this material, it offers excellent oxygen plasma resistance and compatibility with photolithography processes.
3:30 PM - L11.5
Synthesis and Field Emission Properties of Simultaneously Grown Microcrystalline Diamond and Multiwall Carbon Nanotubes.
Kishore Uppireddi 1 , Fabrice Piazza 1 , Brad Weiner 2 , Gerardo Morell 1 3
1 Dept of Physics, University of Puerto Rico, San Juan, Puerto Rico, United States, 2 Dept of Chemistry, University of Puerto Rico, San Juan, Puerto Rico, United States, 3 Dept of Physical Science, University of Puerto Rico, San Juan, Puerto Rico, United States
Show AbstractMicrocrystalline diamond and multiwall carbon nanotubes were grown simultaneously by hot filament chemical vapor deposition (HFCVD) using typical diamond deposition parameters. Iron oxide nanoparticles deposited on the molybdenum substrate served as nanotube catalyst. The hybrid carbon material presents better field emission properties and emission stability compared to microcrystalline diamond or multiwall carbon nanotubes alone. Threshold filed is low as 2.45 V/μm (1μA/cm2) and current densities up to 300μA/cm2. The hybrid material was characterized by micro Raman spectroscopy, high-resolution transmission electron microscopy, electron energy loss spectroscopy and selected area electron diffraction analysis. The macroscopic field emission properties were obtained from a 3mm diameter flat circular anode area placed at a distance of 100 μm.
3:45 PM - L11: FEDs, PDPs
BREAK
L12: Nanomaterials for Displays
Session Chairs
Thursday PM, April 20, 2006
Room 3003 (Moscone West)
4:15 PM - L12.1
Synthesis and in-situ Encapsulation of Manganese doped Zinc Sulfide Nanophospors Using Pulsed Laser Deposition (PLD)
Jeremiah Abiade 1 , Nigel Shepherd 2 3 , David Morton 2 , Eric Forsythe 2 , Dhananjay Kumar 1 4
1 Mechanical Engineering & Chemical Engineering, North Carolina A&T State University, Greensboro, North Carolina, United States, 2 , Army Research Laboratory, Aberdeen, Maryland, United States, 3 Materials Science & Engineering, University of North Texas, Denton, Texas, United States, 4 Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak, Tennessee, United States
Show AbstractThe size dependent properties of luminescent materials have been known for quite sometime. Previous researchers [1] have demonstrated the possibility of obtaining quantum confinement in 3-5 nm colloidal ZnS:Mn nanophosphors. However, conventional techniques are hampered by grain coarsening and particle agglomeration during processing. Furthermore, nano-phosphors must be surface passivated in order to reduce non-radiative recombination and charge trapping from surface states. Before luminescent devices with nanophosphor materials can be realized; reproducible, high-yield synthesis techniques must be developed. We synthesized ZnS:Mn nanoclusters in Al2O3 thin film matrices by alternate ablation of ZnS:Mn and Al2O3 targets during pulsed laser deposition. The size of the ZnS particulates (3-10 nm) was controlled by adjusting the number of laser pulses on the target. Single and multi-layer films (up to 5 layers of ZnS) were prepared using this approach. The luminescence characteristics of the nanocomposites were compared to bulk ZnS:Mn films and are strongly size-dependent. Furthermore, the brightness stability of the Al2O3 passivated nanophosphors is enhanced versus uncoated films. Using this technique we were able to grow and encapsulate self-assembled ZnS:Mn nanoclusters in a high-vacuum environment (~10-7 Torr) without exposure to the ambient. [1] H. Chandler, Materials Science & Engineering R 49, (2005), p. 113
4:30 PM - L12.2
Physical Influences on Photo-emission Wavelength from CdTe Quantum Dot Clusters.
Steve Dunn 1 , Cristina Bertoni 1 , Diego Gallardo 1
1 Nanotechnology, Cranfield University, Cranfield United Kingdom
Show AbstractNanoparticles are increasingly being used in a number of electronic devices to generate light or convert light into electrical energy. When used in a device the specific properties of the nanoparticles that are of interest are the highly tuneable wavelength of emission and high internal quantum efficiencies of recombination leading to light emission. Recently Biju et al , showed that there is a shift in the emission wavelength of quantum dot clusters to the red when they are heated. Earlier work by Tang et al showed that it was possible to change to confinement of electrons in the nanoparticles from 1-D to 2-D chemically. These results may have an impact on the use of quantum dot clusters in electronic devices where local joule heating could cause a shift in the wavelength of light emitted. In this paper we show that temperature can affect the wavelength of light emitted from the quantum dot clusters that are both held in suspension and also deposited in a layer-by-layer process and that there is a non-returnable shift for deposited samples. A comparison is made between the shifts of wavelength of light emitted from the particles held in suspension and those that have been deposited onto glass substrates using l-b-l. A shift towards the red is seen for particles which have previously been attributed to energy transfer from small to larger particles or the development of a new electronic structure due to a rearrangement in packing of the particles. It was found that after cycling to ca. 80°C there was a shift to the red and is similar to that found by Birju et al for QD’s that were in suspension and those that had been deposited onto glass substrates. TEM and SPM (tapping mode) examination of the quantum dots after heating showed that variations in the structure of the dots is responsible for the shift in emission wavelength. In the case of the l-b-l deposited sample a permanent shift to the red is associated with the growth of nanowires which is not seen for the particles in suspension. We have not ruled out the possibility of traps causing a shift in emission but there is a change in the structure of the particles. Our conclusions are that there are wavelength emissions shifts associated with an alteration in packing of the nanoparticles that is substantially non-reversible for l-b-l deposited samples and reversible for particles in suspension.
4:45 PM - L12.3
Surface Potential and Electric Force Gradient Study of IrO2 Nano-emitter Arrays using EFM and SKPM Spectroscopy.
Daniel Chiang 1 , Philip Lei 1 , FengYang Zhang 2
1 Materials Science, Washington State University , Vancouver, Washington, United States, 2 , Sharp Microelectronics Lab., Vancouver, Washington, United States
Show Abstract5:00 PM - L12.4
Carbon Nanocones and Nanodiscs Produced by Slicing the Highly Graphitized Carbon Nanofibers
Cheng-Te Lin 1 , Chi-Young Lee 1 2 , Tsung-Shune Chin 1 , Hsin-Tien Chiu 3
1 Materials Science and Engineering, National Tsing Hua University, Hsinchu Taiwan, 2 Materials Science Center, National Tsing Hua University, Hsinchu Taiwan, 3 Department of Applied Chemistry, National Chiao Tung University, Hsinchu Taiwan
Show AbstractNanostructured carbon materials have attracted interdisciplinary attention due to their potential applications for electronic emission devices, storage media, nanocomposites, and electrode materials. Our recent studies showed that the distinctively herringbone-type carbon nanofiber could be synthesized by using anodic aluminum oxide (AAO) as template and petroleum pitch as precursor. Now we make a further progress to successfully produce a mass nanocone and nanodisc from slicing the herringbone-type nanofiber. After thermal treatment the highly graphitized nanofibers will become fragile. Utilizing the mechanical property, we introduce a mechanical force by sonication to make the treated nanofiber disintegration to form the nanocones or nanodiscs. The diameter is around 300 nm, which depends on the diameter of original nanofiber. The scale of diameter is one order smaller than that synthesized by plasma torch method. The thickness is from several to 100 nm, and in theory the minimum thickness is 5 nm. The range of cone angle measured from nanocone is between 60o to near 180o. A well-aligned nanodisc array will be an excellent adsorbent or storage media due to its high surface area. And the nanocone has potential to develop the novel emission devices.
5:15 PM - L12.5
Nano-sharp Micro-cone Structures on Si Thin Films by Single Pulse Laser Irradiation.
D. G. Georgiev 1 , R.J. Baird 1 , I. Avrutsky 1 , J. Eizenkop 1 , G. Auner 1 , G. Newaz 2
1 Electrical and Computer Engineering, Wayne State University, Detroit, Michigan, United States, 2 Mechanical Engineering, Wayne State University, Detroit, Michigan, United States
Show Abstract