Efficient control of emission and carrier polarity in WS2 monolayer by indium doping

Abstract

Substitutional doping of two-dimensional (2D) transition metal dichalcogenides (TMDs) has been recognized as a promising strategy to tune their optoelectronic properties for a wide array of applications. However, controllable doping of TMDs remains a challenging issue due to the natural doping of these materials. Here, we demonstrate the controllable growth of indium-doped p-type WS2 monolayers with various doping concentrations via chemical vapor deposition (CVD) of a host tungsten (W) source and indium (In) dopant. Scanning transmission electron microscopy confirmed that In atoms successfully substitute the W atoms in the WS2 lattice. Intriguingly, the photoluminescence of the doped sample experiences strong intensity modulation by the doping concentration, which first increases remarkably with an enhancement factor up to ~35 and then decreases gradually when further increasing the doping concentration. Such a phenomenon is attributed to the progressive change of the exciton to trion ratio as well as the defect concentration in the doped samples. The assignment was further verified by the electric behavior of the fabricated In-doped WS2 field effect transistors, which changes regularly from n-type to bipolar and finally to p-type behavior with increasing doping concentration. The successful growth of p-type monolayer WS2 and the dual control of its optical and electrical properties by In doping may provide a promising method to engineer the opto-electronic properties of 2D materials.