Sulfur vacancy-induced reversible doping of transition metal disulfides via hydrazine treatment

Chemical doping of transition metal dichalcogenides (TMDCs) has drawn significant interest because of its applicability to the modification of electrical and optical properties of TMDCs. This is of fundamental and technological importance for high-efficiency electronic and optoelectronic devices. Here, we present a simple and facile route to reversible and controllable modulation of the electrical and optical properties of WS₂ and MoS₂via hydrazine doping and sulfur annealing. Hydrazine treatment of WS₂ improves the field-effect mobilities, on/off current ratios, and photoresponsivities of the devices. This is due to the surface charge transfer doping of WS₂ and the sulfur vacancies formed by its reduction, which result in an n-type doping effect. The changes in the electrical and optical properties are fully recovered when the WS₂ is annealed in an atmosphere of sulfur. This method for reversible modulation can be applied to other transition metal disulfides including MoS₂, which may enable the fabrication of two-dimensional electronic and optoelectronic devices with tunable properties and improved performance.