Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session D30: Organic Field Effect Transistors II |
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Sponsoring Units: DPOLY FIAP Chair: Arthur Epstein, Ohio State Univ. Room: LACC 505 |
Monday, March 21, 2005 2:30PM - 2:42PM |
D30.00001: Ferroelectric Switching in a Polymeric Transistor Peter Jacobson, Jie Xiao, Luis Rosa, Peter Dowben We have exploited the band offset of n-type poly(vinylidene fluoride -- trifluoroethylene) copolymer films to make heterojunction diodes and field effect transistors with polyaniline and polypyrrole. The band offsets have been characterized by photoemission and inverse photoemission. The transistor behavior is strongly influenced by the ferroelectric poly(vinylidene fluoride -- trifluoroethylene). The applied gate voltage can be used to switch the ferroelectric layer, modulating the source to drain current. Nonvolatile polymeric memory elements may be possible. [Preview Abstract] |
Monday, March 21, 2005 2:42PM - 2:54PM |
D30.00002: Characterization of Organic and Carbon Nanotube Electronic Devices Fabricated via Transfer Printing onto Plastic Substrates D.R. Hines, S. Mezhenny, M. Breban, G. Esen, M.S. Fuhrer, E.D. Williams, V.W. Ballarotto Organic and nanotube thin-film transistors (TFT) have been fabricated onto plastic substrates using transfer printing (TP). Transfer printing is a non-lithographic method that has been designed to sequentially assemble high quality TFTs onto plastic substrates. This versatile printing process avoids the use of any chemicals, temperatures or processes that are incompatible with organic materials. Fabricated pentacene TFT devices exhibit saturation, field-effect mobities up to 0.09 cm$^{2}$/Vs and an on/off ratio of approximately $10^{4}$ (similar to devices fabricated on Si wafers with a SiO$_{2}$ dielectric layer). Fabricated carbon nanotube TFT devices exhibit ambipolar behavior and show no hysteresis in the transconductance (in contrast to similar devices fabricated on Si wafers with a SiO$_{2}$ dielectric layer which exhibit only p-type behavior and have a large hysteresis). [Preview Abstract] |
Monday, March 21, 2005 2:54PM - 3:06PM |
D30.00003: Copper-Phthalocyanine Field-Effect Transistor with a Low Driving Voltage Tetsuji Okuda, Susumu Shintoh, Norio Terada Copper-phthalocyanine-thin-film metal-insulator-semiconductor field-effect transistors operating with a low driving voltage have been fabricated by using a PbZr$_{0.5}$Ti$_{0.5}$O$_{3}$ film as a high permittivity insulator layer ($\varepsilon $=500). A field-effect mobility of about 0.017 cm$^{2}$/Vs and an ON/OFF ratio of more than 10$^{3}$ were obtained at gate voltage of - 2V and drain-source voltage of - 1V. This demonstrates operation of a p-type copper-phthalocyanine transistor with a driving voltage low enough for actual device applications. [Preview Abstract] |
Monday, March 21, 2005 3:06PM - 3:18PM |
D30.00004: Rubrene Thin Film Transistors Soonjoo Seo, Byoung-Nam Park, Paul Evans We report on the fabrication and characterization of field-effect transistors formed from rubrene thin films deposited on SiO$_{2}$/Si substrates by thermal evaporation. The growth and electrical properties of rubrene thin films are closely related. Rubrene thin film transistors have a lower saturation field effect mobility, $\sim $ 10$^{-4}$ cm$^{2}$/Vs, than single crystal devices and thin films of other materials. In comparison with pentacene, which initially forms 2D islands, atomic force microscopy shows that rubrene immediately forms circular multilayer islands. We discuss the electrical properties of rubrene transistors based on the geometry of rubrene islands. [Preview Abstract] |
Monday, March 21, 2005 3:18PM - 3:30PM |
D30.00005: Effect of using split-gate electrodes on a pentacene based field effect transistor Nicholas Pinto, Carl Mueller, Noulie Theofylaktos, Alan Johnson, Felix Miranda We present our results of using split-gate electrodes on an evaporated film of pentacene in a field effect transistor configuration. Pentacene was purchased from Aldrich and used as received. Two split-gate electrodes, each 20 $\mu $m wide and separated by 4 $\mu $m were patterned on a Si/SiO$_{2}$ substrate over which an additional 100 nm of SiO$_{2}$ was grown. Source (S) and drain (D) electrodes were evaporated onto the substrate, centered on the buried split-gate structure. Finally, a pentacene film of thickness 500 nm was evaporated onto the patterned substrate in vacuum (2x10$^{-5}$ mbar). Current voltage characteristics of this device show negligible S/D drain current under S/D biases up to -10V with either or both gates turned ``off'' (gate electrodes grounded) but does show an increase of about two orders of magnitude in the S/D current (at a S/D bias of -10V) when both gates are turned ``on'' with a voltage of -12 V. Several devices were tested and gave similar results. Based on these results the device can be treated as two gate controlled switches placed in series and is analogous to a logic AND gate. [Preview Abstract] |
Monday, March 21, 2005 3:30PM - 3:42PM |
D30.00006: Photoinduced charge transfer in bifunctional molecules with both electron donor and accepter groups J. H. Park, Y. Wu, J. Parquette, A. J. Epstein, P. Padmawar, L. Y. Chiang Charge transfer within photo-active molecules is one of the important mechanisms for achieving photo-sensitive devices. We have employed two kinds of material, C$_{60}$- diphenylaminofluorene-C$_{18}$ [1] and an intramolecularly hydrogen-bonded, porphyrin-terminated dendron with a focal napthylene diimide [2]. Both have electron donor and accepter groups in a molecule. For the former, we made the structure by sandwiching a film of the photo-active material between ITO electrodes to measure photoconductivity spectrum in near- UV/Vis/near-IR range. Photoconductivity is on order of $10^{-12} $S/cm and it is dependent on light intensity and wavelength. As light intensity increases, photoconductivity increases for $\lambda \sim$ 350nm, but it decreases for $\lambda \sim$ 650nm. For the latter, we made photovoltaic cells with aluminum and ITO electrodes. IV characteristics were measured at each spectrum peak of donor (414, 516, 552, 590, 646nm) and accepter (360, 382nm) absorption. At 516, 552 nm, the devices shows highest power conversion efficiency with V$_{oc} \sim$ 0.8 V and J$_{sc} \sim 5 \times 10^{-8}$A/cm$^2$. The mechanisms and measurements of temperature dependence will be discussed. [1] H. Luo {\it et. al}, J. Phys. Chem. B 107, 9312 (2003). [2] Y. Wu {\it et. al.} to be published [Preview Abstract] |
Monday, March 21, 2005 3:42PM - 4:18PM |
D30.00007: Synergistic Processes At Optically-Active Membrane-Protein, Conducting Polymer Interfaces Invited Speaker: Bacteriorhodopsin (bR), a protein existing in the halobacterial purple membrane serves as a light driven pump which sets up an electrochemical gradient and transports protons across the cell membrane. We have explored the synergetic processes at the conducting polymer/bR interface due to photoexcitation in presence of a voltage bias. Several interesting features in the photoelectric signal characteristics are observed from systems consisting of oriented-bR films on conducting polymer substrates. The possibility of changing the oxidation state of the polymer electrochemically is coupled to the optically-activated proton gradient in the bR side in this unique hybrid system. It was recently demonstrated that the internal conversion of the intermediate deprotonated M state of bR and the proton transfer/transport can be controlled by the electrochemical reactions at the adjacent poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) layer and leads to interesting device prospects in the process.$^{1,2}$ We generalize the principles involved by studying variety of mutant forms of bR and conducting polymers with different doping levels. The implications of coupling the biophysical events in bR with the electrochemical processes of the conducting polymer in terms of interesting wavelength- dependent photodiode features and photo-electrochemical transistor action will be discussed. \\ 1. A. G. Manoj and K. S. Narayan, Appl. Phys. Lett., 83, 3614 (2003). \\ 2. A. G. Manoj and K. S. Narayan , Biosens. and Bioelectr. J., 10, 967 (2004). [Preview Abstract] |
Monday, March 21, 2005 4:18PM - 4:30PM |
D30.00008: Ab Initio Study of Polarizabilities of Oligothiophene, Oligocyclopentadiene and Oligofulvene and their Cyano Substituted Oligomers Jolanta Lagowski, Sultana Ferdous Ab Initio polarizabilities of thiophene, fulvene and cyclopentadiene based conducting oligomers and polymers and their cyano derivatives have been calculated using the Hartree-Fock (HF), configuration interaction (singles) (CIS ) and density functional (DF) theories with 3-21G* basis using Gaussian software. The main motivation of this investigation is to determine the correlation between the excitation energies and polarizabilities for the conjugated systems studied. It has been found that HF and DF approaches give similar magnitudes for polarizabilities whereas CIS theory provides results that are considerably different. All three methods predict similar trends in polarizabilities as a function of oligomer length and bond alternation along the backbone of the oligomers. It has also been observed that the end groups and the number of `double' bonds have a significant effect on the magnitude of polarizability per C-C bond. Comparison with experimental results will be made where possible. [Preview Abstract] |
Monday, March 21, 2005 4:30PM - 4:42PM |
D30.00009: Patterned Conducting Polymer Microelectronics for Analysis of Neural Signaling Daniel T. Simon, S. A. Carter The ion-mediated conduction and versatility of device-fabrication of conducting polymers provide a route to the study of signaling in neural networks. To this end, network patterned junctions of conducting polypyrrole have been electropolymerized on commercially available micro-electrode arrays. The typical dimensions are 200~$\mu$m between electrodes, each electrode being 30~$\mu$m in diameter. Tetrabutylammonium perchlorate or sodium p-toluenesulfonate were used as electrolyte in the organic solvent. Individual polypyrrole junctions, when synthesized and connected in a three-electrode configuration, exhibit current-switching behavior analogous to synaptic weighting or neural ``learning.'' Junctions copolymerized with polythiophene exhibit current rectification and the non-linear current-voltage behavior requisite for neural electronics (\emph{i.e.} the activation function). [Preview Abstract] |
Monday, March 21, 2005 4:42PM - 4:54PM |
D30.00010: Synthesis and Electrical Properties of Nanorods and Nanotubes of Poly(3-hexylthiophene) Adrian Southard, Seungil Cho, Miriam Berdichevsky, Michael Fuhrer, Sang Jun Son, Sang Bok Lee Nanorods and nanotubes (diameter 50 - 200 nm) of poly(3-hexylthiophene), P3HT, an organic semiconductor, were synthesized by electrochemical polymerization in a porous alumina template. FET devices have been constructed with a conducting channel of P3HT nanorods contacted by gold source and drain electrodes patterned on a SiO$_{2}$/Si substrate using e-beam lithography. Synthesis, characterization, and electrical measurements of the P3HT nanorods and nanotubes will be reported. [Preview Abstract] |
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