Abnormal n-type doping effect in nitrogen-doped tungsten diselenide prepared by moderate ammonia plasma treatment

To facilitate potential applications of tungsten diselenide (WSe₂) in electronics, controllable doping is of great importance. As an industrially compatible technology, plasma treatment has been used to dope two-dimensional (2D) materials. However, owing to the strong etching effect in transition metal dichalcogenides (TMDCs), it is difficult to controllably dope 2D WSe₂ crystals by plasma. Herein, we develop a moderate ammonia plasma treatment method to prepare nitrogen-doped WSe₂ with controlled nitrogen content. Interestingly, Raman, photoluminescence, X-ray photoelectron spectroscopy, and electrical measurements reveal abnormal n-doping behavior of nitrogen-doped WSe₂, which is attributed to selenium anion vacancy introduced by hydrogen species in ammonia plasma. Nitrogen-doped WSe₂ with abnormal n-doping behavior has potential applications in future TMDCs-based electronics.