Ultraviolet Light-Induced Persistent and Degenerated Doping in MoS2 for Potential Photocontrollable Electronics Applications.

Efficient modulation of carrier concentration is fundamentally important for tailoring the electronic and photoelectronic properties of semiconducting materials. Photoinduced doping is potentially a promising way to realize such a goal for atomically thin nanomaterials in a rapid and defect-free manner. However, the wide applications of photoinduced doping in nanomaterials are severely constrained by the low doping concentration and poor stability that can be reached. Here, we propose a novel photoinduced doping mechanism based on the external photoelectric effect of metal coating on nanomaterials to significantly enhance the achievable doping concentration and stability. This approach is preliminarily demonstrated by an MX2 (M is Mo or Re; X is S or Se) nanoflake modified through a simple process of sequentially depositing and annealing an Au layer on the surface of the flake. Under ultraviolet (UV) light illumination, the modified MX2 achieves degenerated n-type doping density of 1014 cm-2 rapidly according to the experimentally observed >104 times increment in the channel current. The doping level persists after the removal of UV illumination with a nonobservable decrease over 1 day in vacuum (less than 23% over 7 days under an ambient environment). This photoinduced doping approach may contribute a major leap to the development of photocontrollable nanoelectronics.