High-mobility Organic Single-crystal Transistors with Amorphous Fluoropolymer Gate Insulators
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1091-AA11-53
High-mobility Organic Single-crystal Transistors with Amorphous Fluoropolymer Gate Insulators Mayumi Uno1, Yukihiro Tominari2, and Jun Takeya2 1
Technology Research Institute of Osaka Pref., Izumi, Osaka, 594-1157, Japan
2
Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
ABSTRACT High-mobility rubrene single-crystal field-effect transistors are built on highly water- and oil-repellent fluoropolymer gate insulators. Roughness is intentionally introduced at the surface once to provide good adhesion to metal films and photoresist polymers for stable bottom electrodes. Before constructing interfaces with rubrene crystals, smoothness of the fluoropolymer surface is recovered by annealing at a moderate temperature to maximize mobility of the carriers induced near the interfaces. The estimated mobilities in the saturation region reproducibly exceeded 15 cm2/Vs for all the ten devices fabricated in this method and reach 30 cm2/Vs for the best two samples among them. The results demonstrate that the water-repellency and smoothness of the dielectric polymers are favorable in the excellent transistor performance. INTRODUCTION One of the most intriguing questions on organic field-effect transistors (OFETs) is their maximum performance achievable with somewhat idealized devices. Technically, it is essential for putting them into practical use for high-speed applications such as logic-circuit components. Recent development of single-crystal field-effect transistors (SC-OFETs) has allowed us to induce carriers in the vicinity of atomically flat organic crystals without grain boundaries and to study fundamental mechanism of the carrier transport [1-3]. Very recently, carrier mobility ยต up to 40 cm2/Vs was reported for rubrene SC-OFETs as the result of the four-terminal measurements avoiding the contact resistances of the source and drain electrodes [4], indicating the material potential much higher than realized in organic polycrystals. We note, however, that their performances as practical devices were not necessarily satisfactory because of low reproducibility of the performances, poor saturation in the output characteristics, and lower mobility (less than 20 cm2/Vs) in the two-terminal evaluation. Therefore, further development has been required to link the high intrinsic carrier mobility of the organic semiconductors to practical applications of high-performance logic circuitry. In this study, we report on significant improvement in the current amplification performance in high-mobility rubrene SC-OFETs incorporating water- and oil-repellent
fluoropolymer gate insulators. Since moisture and other contaminations are reported to provide trap levels at the interface between semiconductors and gate dielectrics [5], the use of the fluoropolymer is expected to be useful to improve the device performances. It was indeed reported that the devices with such polymer dielectric layers showed significant improvement in their bias-stressing and subthreshold properties, though the mobility wa
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