Selective Surface Modification and Layer Thinning of MoS₂ via Ultraviolet-Light Irradiation in an Ionic Solution: Implications for Multifunctional Nanoelectronic Devices

The electrical properties of transition-metal dichalcogenides (TMDs), such as MoS₂, are highly dependent on carrier doping and layer thickness. The ability to selectively control these two critical characteristics is of great importance in order to develop TMD-based multifunctional nanoelectronic device applications, which remains challenging. Here, we report a strategy for controllable surface modification and layer thinning of MoS₂ via ultraviolet (UV)-light irradiation in a silver ionic (Ag⁺) solution environment. The results show that, by adjustment of the UV irradiation time, nanostructured Ag ultrathin films (∼2.9 nm) are uniformly deposited on monolayer MoS₂ and can lead to a controllable p-type doping effect, while the thickness of MoS₂ from few-layer to thick-layer could be thinned to the atomic monolayer limit. Both Ag nanostructure deposition and layer thinning have been evidenced to initiate from the edges of MoS₂, independent of the edge type, thus revealing a unique UV-light-assisted defect-induced surface modification and layer-thinning mechanism. Overall, this study provides a simple methodology for the selective control of doping and layer thickness in TMDs, paving the way for developing multifunctional nanoelectronics and integrated optoelectronics.