Solid-State and Nano Seminar
Two Dimensional Dichalcogenides-ZnO Nanowire Hybrid Devices
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Two dimensional (2D) dichalcogenide MoS2 and WSe2 nanosheets appear as new 2D semiconductors compensating some weakness of graphene, being investigated for field-effect transistors (FETs), photo-detectors, and even logic circuits for NAND, NOR, small signal amplifier, and ring oscillators. However, good circuits using 2D based-FETs generally need electron beam (E-beam) lithography, since the 2D nanoflakes are not large enough to pattern by photolithography. Therefore, 2D MoS2-based circuits are not that easy to be realized on one substrate by photolithography although a few exceptional cases were reported. Hence, more favorable and simple way to use MoS2-based device may be necessary.
We demonstrate a hybrid inverter-type nanodevice comprised of MoS2 nanoflake field-effect transistor (FET) and ZnO nanowire (NW) Schottky diode (SD) on one substrate, aiming at 1 dimensional (1D)-2 dimensional (2D) hybrid integrated electronic circuit with low power consumption, high gain, and photo-detection. In the present work, we used direct imprinting method using polydimethylsiloxane (PDMS) for the fabrication of patterned bottom-gate MoS2 nanosheet FETs, so that they should be located near ZnO NW SDs which were initially-fabricated. The ZnO NW SD and MoS2 patterned bottom-gate FET (BG-FET) worked respectively as load and driver for an electrical logic inverter, which exhibits a high voltage gain of ~50 at supply voltage (VDD) of 5V and also shows a low power consumption of less than 50 nW. Moreover, we also demonstrate a complementary inverter (CMOS-type) with p-channel WSe2 and n-ZnO nanowire, using the same direct imprinting technique. Subnanowatt power consumption and high gain over 60 along with high switching speed were achieved from the CMOS inverter. We thus conclude that our 1D-2D hybrid nano-inverter is quite promising for both logic and photo-sensing applications due to its performance, simple device configuration, and simple fabrication method.
Seongil Im, male, applied physicist and device engineer was born in Korea 1962 and earned his BS from the dept. of Metallurgical Engineering at Yonsei University, Seoul Korea in 1984. After spending several years in Korea as researchers, he moved to Univ. of California at Berkeley for his Ph.D study in Materials Science and Engineering. He achieved Ph.D from UC at Berkeley in 1994 and worked as a research fellow at the dept. of Applied Physics and Electrical Engineering, California Institute of Technology (CALTECH) from 1995 till 1996. He joined the dept. of Materials Science and Engineering at Yonsei Univ. as an assistant professor in 1997. However, in 1999 he moved to the dept. of Physics of the same university as an associate professor. His research expertise is device physics and detailed research subjects are Oxide and Organic Thin-Film Electronics, Field Effect Transistors, Nanowire and Nanosheet FETs, and Photon-probe device characterizations for stabilities. Currently, he is a professor in the dept. of Physics at Yonsei. He has published more than ~220 peer-review journal papers including Applied Physics Letters, Advanced Materials, Advanced Functional Materials, Small, Nano Letters, IEEE Electron Device Letters.