N- and p-type doping of transition-metal dichalcogenides by Ar plasma treatment and its application in CMOS

Abstract

Doping of two-dimensional (2D) semiconductors is necessary to achieve high performance and low power consumption in optoelectronic and logic devices. Herein, we report controllable p- and n-type doping of the transition-metal dichalcogenides (TMDs), tungsten diselenide (WSe2), and molybdenum ditelluride (MoTe2) via argon (Ar) plasma treatment. The doping of TMDs was tuned by controlling Ar plasma treatment conditions. The desired n-type doping in WSe2 and MoTe2 was obtained by applying a short treatment time, resulting in increased electron current and an upshift in binding energy. Owing to prolonged plasma treatment, abnormal p-type doping was achieved in WSe2 and MoTe2. Increased hole current, downshift in binding energy, appearance of oxygen bonds (O–W, Mo, Se, and Te), and redshift in Raman peaks revealed that the abnormal p-type doping behavior for WSe2 and MoTe2 was owing to considerable vacancies and edge defects induced in the top layer of TMDs by Ar plasma treatment. These were immediately occupied by oxygen atoms or oxidized to introduce oxygen doping when TMDs were exposed to air. The formation of a homogeneous oxide film on the top layer of TMDs was further demonstrated by the smooth surface and higher thickness of TMDs with heavy p-type doping compared to those of the pristine sample. A complementary metal-oxide-semiconductor (CMOS) inverter based on p- and n-WSe2 was demonstrated herein. Our study proposes a controllable way to modulate the doping type of TMDs, which has potential applications in the performance modulation of devices, design of novel device structures, and realization of 2D material-based logic circuits.