Low-power and Fast-switching Organic Field-effect Transistors with Ionic Liquids
- PDF / 480,806 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 8 Downloads / 164 Views
1082-Q05-05
Low-power and Fast-switching Organic Field-effect Transistors with Ionic Liquids S. Ono1, S. Seki1, R. Hirahara2, Y. Tominari2, and J. Takeya2 1 Materials Science Research Laboratory, CRIEPI, Komae, Tokyo, 201-8511, Japan 2 Graduate Schools of Science, Osaka University, Machikaneyama, Toyonaka, 560-0043, Japan ABSTRACT We report high-mobility rubrene single-crystal field-effect transistors with ionic-liquid electrolytes used for gate dielectric layers. As the result of fast ionic diffusion to form electric double layers, their capacitances remain more than 10 µF/cm2 even at 0.1 MHz. With high carrier mobility of 1.2 cm2/Vs in the rubrene crystal, pronounced current amplification is achieved at the gate voltage of only 0.2 V, which is two orders of magnitude smaller than that necessary for organic thin-film transistors with dielectric gate insulators. The results demonstrate that the ionic-liquid/organic semiconductor interfaces are suited to realize low-power and fastswitching field-effect transistors without sacrificing carrier mobility in forming the solid/liquid interfaces. INTRODUCTION Field-effect transistors (FETs) based on organic semiconductors have been extensively investigated for the recent decade, in which realizing high-mobility, low-power, and fastswitching devices has been a central subject to take the best advantage of their simple and lowcost production processes [1]. For this purpose, the material combination in the layered structure of organic FETs is being intensively studied because the interfacial phenomena are crucial in determining their device performances. While most of the studies for device applications are based on thin-film organic polycrystalline semiconductors, organic single-crystal FETs have advantages to study the intrinsic material potentials and the interfacial properties both at the semiconductor-electrode and the semiconductor-insulator boundaries in the absence of the grain boundaries [2-4]. Recently marked progresses in the studies of the single-crystal transistors have been achievements of mobility exceeding 20 cm2/Vs [5-8], which is already much higher than that of amorphous silicon transistors, and detection of the normal Hall effect, evidencing the band-like transport mechanism [9,10]. Most common gate dielectrics used for the organic FETs are typically 100-500 nm thick SiO2 or polymer layers, whose capacitances are in the range of 5-30 nF/cm2. With such relatively low capacitance, the maximum carrier density is limited in the order of 1013 cm-1 even at the gate voltage VG of 100 V, which is already close to dielectric breakdown [11]. As one of the alternative methods to accumulate carriers more efficiently, there has been significant interest in making use of electrolytes. When VG is applied to the electrolytes, electric double layers (EDLs) are formed after the ionic redistribution, so that VG is sustained only at typically 1 nm thick EDLs. As the result, capacitance of the EDLs exceeds ~ 10 µF/cm2, meaning that orders of magnitude higher density carriers a
Data Loading...
