Flexible organic field-effect transistors fabricated by the electrode-peeling transfer
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Flexible organic field-effect transistors fabricated by the electrode-peeling transfer Takeshi Yasuda, Katsuhiko Fujita and TetsuoTsutsui Department of Applied Science for Electronics and Materials, Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580, Japan ABSTRUCT We report a simple and mild fabrication of flexible organic field-effect transistors (OFETs) by an electrode-peeling transfer method. Firstly, fine patterns of source-drain metal electrodes were formed on a solid substrate, where a micro-patterning process such as photolithography is applicable. An organic dielectric layer (poly-chloro-p-xylylene) was deposited by a chemical vapor deposition. Then patterned gate electrode was deposited using a shadow mask. On the top surface of the gate electrode, another adhesive flexible substrate was fixed and the stack of the flexible substrate /gate electrode /dielectric layer /source-drain electrode was peeled away from the solid substrate. The peeling-transfer was completed with a help of a self-assembled monolayer of n-decyl mercaptan as a connecting buffer layer between the gold electrodes and the dielectric layer. Then an organic semiconductor material was deposited on the fresh peeled-off surface on the flexible substrate. When pentacene was used as the semiconductor material, the OFETs exhibited a hole mobility of 0.1 cm2/Vs and a current on/off ratio of 105. INTRODUCTION Much progress has been shown in the research and development in organic and polymeric field-effect transistors in recent years [1,2]. They have the potentials to be low-cost, lightweight and mechanically flexible, compared with the conventional silicon technology. Concerning fabrication technique, OFETs have been fabricated by an ink-jet printing [3] or dry printing technology [4], which can produce a fine structure of conductive polymers for source-drain and gate electrodes on a flexible plastic substrate. From the viewpoints of durability and conductivity, metal electrodes should be suitable rather than conductive polymer electrodes especially for the source-drain electrodes. Finely structured metal electrodes are fabricated by a vacuum deposition through a resist patterned by a photolithograph and lift-off or by a micro-contact printing and etching [5]. In the point of being flexible, a polymeric dielectric layer and a plastic substrate have significant advantages over a conventional glass substrates or silicon one. However, when such flexible materials are used for organic electronic devices, one problem arises that it is difficult to pattern the detailed metal electrodes using a conventional photolithography and wet etching process. Therefore, materials withstanding the procedures have been chosen carefully for the substrate as long as forming the finely structured electrode directly on a flexible substrate. In this study, we propose a way to fabricate a flexible OFET, electrode-peeling transfer method. In this method, source-drain and gate electrodes formed with a metal on a rigid temporary subs
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