Large-domain Organic Crystalline Films for Field-effect Transistors
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1091-AA05-73
Large-domain Organic Crystalline Films for Field-effect Transistors Y. Tominari1, M. Uno1,2, M. Yamagishi1, Y. Suzuki3,4, A. Wakamiya3,4, S. Yamaguchi3,4, and J. Takeya1 1
Osaka University, Toyonaka, 560-0043, Japan
2
TRI-Osaka, Izumi, 594-1157, Japan
3
Nagoya University, Nagoya, 464-8602, Japan
4
SORST-JST, Kawaguchi, 332-0012, Japan
ABSTRACT We report a method to fabricate thin films of large-domain organic semiconductor single crystals dispersed over the whole surface of centimeter-scale substrates for field-effect transistors. Growing less than 500-nm thick film-like organic crystals of sub-millimeter sizes densely in a furnace independently of substrates by physical vapor transport, the collection of the single crystals is mechanically attached to the surface of gate dielectric layers. The organic transistors made of large-domain benzo-annulated pentathienoacene crystals exhibited pronounced transistor performances with mobility values of ~ 0.2-2 cm2/Vs, which is as high as devices of one-piece crystals. The result demonstrates that the above technique provides a method to apply high performance of organic single crystal transistors to real circuitry devices on large-area substrates.
INTRODUCTION Organic field-effect transistors (OFETs) are of broad industrial interest because of their potential applications for circuit-controlling elements of organic light-emitting displays and rewritable papers, for examples. However, it is still challenging to achieve sufficient performances for high-speed applications such as logic circuit components and to consider further extensive market on such technologies. So far, the highest mobility reported for the OFETs is 20-40 cm2/Vs, which is realized in rubrene single crystal transistors [1-3]. Although the performance gives an intrinsic transport property of organic semiconductor materials, the single crystal devices themselves have been rarely considered for industrial production because the sample preparation usually require human processes. In this presentation, we report our attempt to cover a whole
a-few-cm2 substrate with thin organic crystal films and show their performances as OFETs. The present method is distinctive in the producing single crystals completely independent of substrates; submillimeter-size film-like crystals are naturally grown in a tube furnace of their own and a collection of them are closely attached to the substrate electrostatically. Therefore, it provides conceptually the closest way to realize the same single crystal / dielectric interfaces that have given rise to the highest performance of the organic single crystal transistors reported [1,4], though there have been reports to grow organic single crystals directly on substrates [5].
EXPERIMENTAL Device preparation We first grew single crystals of benzo-annulated pentathienoacene (f-B5TB) by the physical vapor transport technique. We previously reported that stand-alone single crystal OFETs made of the compound has excellent air stability and fairly good mobility values
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