Ultrathin oxysulfide semiconductors from liquid metal: a wet chemical approach

Metal oxychalcogenides are emerging as a new motif of group VI-A semiconductors with unique electronic properties. Among this family, two dimensional (2D) oxysulfide materials have been increasingly involved in the development of next-gen electronic and optoelectronic devices. However, current synthesis routes for 2D metal oxysulfides are still limited to vapor phase deposition techniques, hindering access to ultra-thin, well-defined, and highly crystalline structures. Herein, we report a new synthesis approach for atomically thin and large-area indium oxysulfide nanosheets (2D In 2 O 3− x S x , x is from 0 to 0.41). The process consists of printing indium oxide skins out of molten indium metal and a subsequent sulfur insertion conducted in a trisulfur radical anion solution. Back-gated field-effect transistors (FETs) based on 2D In 2 O 3− x S x reveal a notably high electron mobility of ∼20.4 cm 2 V −1 s −1 , corresponding to approximately 270% mobility enhancement over as-synthesized indium oxide. In addition, 2D In 2 O 3− x S x based photodetectors exhibit an excellent performance in ultraviolet (UV) region, with a photoresponsivity of ∼3.4 × 10 3 A W −1 greatly surpassing that of many commercial materials. More importantly, the same reaction parameters can be employed to obtain 2D bismuth oxysulfide and 2D tin oxysulfide, offering a furnace-free approach for 2D oxysulfide semiconductor fabrication. Liquid metal chemistry offers a new pathway towards the creation of functional 2D metal oxysulfides.