Impurity-Induced Emission in Re-Doped WS2 Monolayers

Impurity doping is a viable route toward achieving desired subgap optical response in semiconductors. In strongly excitonic two-dimensional (2D) semiconductors such as transition metal dichalcogenides (TMDs), impurities are expected to result in bound-exciton emission. However, doped TMDs often exhibit a broad Stokes-shifted emission without characteristic features, hampering strategic materials engineering. Here we report observation of a well-defined impurity-induced emission in monolayer WS2 substitutionally doped with rhenium (Re), which is an electron donor. The emission exhibits characteristics of localized states and dominates the spectrum up to 200 K. Gate dependence reveals that neutral impurity centers are responsible for the observed emission. Using GW-Bethe-Salpeter equation (GW-BSE) calculations, we attribute the emission to transitions between spin-split upper Re band and valence band edge.

Automated summary

Impurity doping is a viable approach for improving optical response in semiconductors, but can lead to broad emissions that hinder materials engineering. In this study, a well-defined impurity-induced emission was observed in rhenium-doped monolayer WS2, with neutral impurity centers responsible for the emission. Additionally, calculations suggest that the emission is attributed to transitions between spin-split upper Re band and the valence band edge.