Chemical Dopant-Free Doping by Annealing and Electron Beam Irradiation on 2D Materials

Abstract

Doping is a key technique for forming complementary metal-oxide-semiconductor (CMOS) that is a basic building block for current state-of-the-art semiconductor devices. However, conventional doping methods such as ion implantation are unsuitable for 2D materials due to their ultra-thinness to accommodate substitutionally doped atomic structures and vulnerability to high energy ion bombardment. Chemical doping methods have been widely used for 2D materials to induce a charge exchange transfer; however, they are subjected to surface contamination which can be detrimental for high quality semiconductor device processing. In this work, the authors reveal the effects of chemicals-free doping in which annealing induces a p-doping effect by physisorption and substitution of oxygen atoms while electron beam irradiation selectively n-dopes MoTe2, based on the results obtained by electrical characterization and Kelvin probe force microscopy. The annealing increases work-function of MoTe2 which undergoes oxidation as observed in the reduction of surface potential and the transition of transfer curves toward the p-type behavior. Electrical measurements and a significant reduction in surface potential after electron beam irradiation indicate the generation of trapped charges which is responsible for the n-doping effect. Subsequently, the authors fabricate a CMOS inverter consisting of distinctively p- and n-doped areas of MoTe2.