Electron beam lithography induced doping in multilayer MoTe2

Abstract Molybdenum ditelluride (MoTe2) is an excellent building block for assembling switching devices owing to its appropriate band gap, tunable p- and n-type conduction. Electron beam lithography (EBL) as a powerful method for electronic device fabrication, generally involves thermal process for resist solidification and electron beam writing. Herein, we find that thermal processing in air and electron beam irradiation result in significant p- and n-doping in multilayer MoTe2, respectively. The p- and n-doping levels can be precisely controlled by the annealing temperature (time) and injection Cullen density, respectively. Both p-doping by annealing and n-doping using irradiation are reversible and can realize degenerate-like conduction behavior. The annealing-induced adsorption of molecules as electron acceptors (e.g. O2, H2O) on the surface MoTe2 accounts for the p-doping, whereas irradiation-induced desorption and interface charging are probably responsible for the n-doping. Polymethyl methacrylate (PMMA) coating does not completely hinder but mitigate the p-doping by annealing. In contrast, PMMA coating is invalid in inhibition of the n-doping by irradiation. These findings would promote understanding of the transport properties of intrinsic MoTe2. Besides, the facile, reversible and controllable p- and n-doping methods are helpful for assembling novel electronics with diverse functionality.