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.