Ambipolar Transport in Phosphorus-Implanted WS₂ Monolayers

The doping of two-dimensional (2D) transition metal dichalcogenides (TMDCs) by an approach compatible with circuit integration is crucial. However, ion implantation, the most commonly used method for doping semiconductors, poses significant challenges for 2D-TMDCs because of the requirement for ultralow ion energy and the difficulty of restoring damaged 2D materials. Here, we achieve bipolar transport in intrinsic n-type WS2 monolayers through phosphorus (P) ion implantation using commercial ion implanters. Millisecond flash lamp annealing is employed to remove ion-induced defects and activate P. Experimental results show a clear change in carrier type with increasing ion fluence. Samples implanted with a fluence of 7.5 × 1012 cm–2 display ambipolar transport behavior with an on/off ratio of 4.4 × 105 and 1.6 × 106 for p- and n-branch, respectively. At the same time, the optical and structural properties of WS2 are well preserved. All of these findings not only complement the fundamental understanding of 2D-TMDCs but also provide a possible route for heterointegration of TMDCs into current Si-based semiconductor technologies.