Spatial control of the threshold voltage of low-voltage organic transistors by microcontact printing of alkyl- and f luo
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Spatial control of the threshold voltage of low-voltage organic transistors by microcontact printing of alkyl- and fluoroalkyl-phosphonic acids Ikue Hirata, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan Ute Zschieschang and Frederik Ante, Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany Tomoyuki Yokota and Kazunori Kuribara, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan Tatsuya Yamamoto and Kazuo Takimiya, Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8527, Japan Masaaki Ikeda and Hirokazu Kuwabara, Functional Chemicals RD Laboratories, Nippon Kayaku Co., Ltd., Kita, Tokyo 115-8588, Japan Hagen Klauk, Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany Tsuyoshi Sekitani, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan Takao Someya, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan; Institute for Nano Quantum Information Electronics, The University of Tokyo, Meguro-ku, Tokyo 153-8505, Japan Address all correspondence to Takao Someya at [email protected] (Received 24 May 2011; accepted 16 August 2011)
Abstract Low-voltage-driven organic thin-film transistors (organic TFTs) with spatially controlled threshold voltages (−1.2 and −0.36 V) were fabricated for the first time. Using the microcontact printing method, tetradecylphosphonic acid (HC14-PA) and pentadecylfluoro-octadecylphosphonic acid (FC18-PA) were transferred to form ultrathin layers in different regions on a substrate. Together with plasma-grown aluminum oxide (AlOx) layer, the stamped layers were shown to have equal insulating ability as the dipped method monolayer. The feasibility of the area-selective stamping method was displayed using locally controlled inverter circuits. The shift of turn-on voltage for those transistors was consistent with the threshold voltage shift of the transistors.
Recently, organic thin-film transistors (organic TFTs) have attracted attention because they are a key element in realizing a new class of devices such as flexible displays,[1,2] radio frequency identification tags,[3] and large-area sensor arrays.[4] As a result of organic transistor technology advancement, large-scale integration such as processors[5] and shift registers[6,7] has become possible. An important prerequisite for the reliable operation of such highly complex circuits are large noise margins that are indispensable for the successful suppression of inadvertent switching events in the unavoidable presence of electronic noise.[8] Large noise margins in turn require precise and deterministic control of the threshold voltage of the transistors. Doping is widely used in inorganic transistors to control threshold voltage; however, many dopants are unstable and diffuse into organic materials, which makes it difficult to control the threshold voltage in organic transistors. Alternatively, surface modificat
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