title: Controllable nondegenerate p-type doping of tungsten diselenide by octadecyltrichlorosilane.
abstract: Despite heightened interest in 2D transition-metal dichalcogenide (TMD) doping methods for future layered semiconductor devices, most doping research is currently limited to molybdenum disulfide (MoS2), which is generally used for n-channel 2D transistors. In addition, previously reported TMD doping techniques result in only high-level doping concentrations (degenerate) in which TMD materials behave as near-metallic layers. Here, we demonstrate a controllable nondegenerate p-type doping (p-doping) technique on tungsten diselenide (WSe2) for p-channel 2D transistors by adjusting the concentration of octadecyltrichlorosilane (OTS). This p-doping phenomenon originates from the methyl (-CH3) functional groups in OTS, which exhibit a positive pole and consequently reduce the electron carrier density in WSe2. The controlled p-doping levels are between 2.1 × 10(11) and 5.2 × 10(11) cm(-2) in the nondegenerate regime, where the performance parameters of WSe2-based electronic and optoelectronic devices can be properly designed or optimized (threshold voltage↑, on-/off-currents↑, field-effect mobility↑, photoresponsivity↓, and detectivity↓ as the doping level increases). The p-doping effect provided by OTS is sustained in ambient air for a long time showing small changes in the device performance (18-34% loss of ΔVTH initially achieved by OTS doping for 60 h). Furthermore, performance degradation is almost completely recovered by additional thermal annealing at 120 °C. Through Raman spectroscopy and electrical/optical measurements, we have also confirmed that the OTS doping phenomenon is independent of the thickness of the WSe2 films. We expect that our controllable p-doping method will make it possible to successfully integrate future layered semiconductor devices.
authors: School of Electronics & Electrical Engineering and ‡SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University , Suwon 440-746, Korea.
authors: Dong-Ho
authors: DH
authors: Kang
authors: Jaewoo
authors: J
authors: Shim
authors: Sung Kyu
authors: SK
authors: Jang
authors: Jeaho
authors: J
authors: Jeon
authors: Min Hwan
authors: MH
authors: Jeon
authors: Geun Young
authors: GY
authors: Yeom
authors: Woo-Shik
authors: WS
authors: Jung
authors: Yun Hee
authors: YH
authors: Jang
authors: Sungjoo
authors: S
authors: Lee
authors: Jin-Hong
authors: JH
authors: Park
keywords: OTS; WSe2; electronic device; nondegenrate doping; optoelectronic device