Tunable Schottky barrier width and enormously enhanced photoresponsivity in Sb doped SnS₂ monolayer

Doping, which is the intentional introduction of impurities into a material, can improve the metal-semiconductor interface by reducing Schottky barrier width. Here, we present high-quality two-dimensional SnS₂ nanosheets with well-controlled Sb doping concentration via direct vapor growth approach and following micromechanical cleavage process. X-ray photoelectron spectroscopy (XPS) measurement demonstrates that Sb contents of the doped samples are approximately 0.22%, 0.34% and 1.21%, respectively, and doping induces the upward shift of the Fermi level with respect to the pristine SnS₂. Transmission electron microscopy (TEM) characterization exhibits that Sb-doped SnS₂ nanosheets have a high-quality hexagonal symmetry structure and Sb element is uniformly distributed in the nanosheets. The phototransistors based on the Sb-doped SnS₂ monolayers show n-type behavior with high mobility which is one order of magnitude higher than that of pristine SnS₂ phototransistors. The photoresponsivity and external quantum efficiency (EQE) of Sb-SnS₂ monolayers phototransistors are approximately three orders of magnitude higher than that of pristine SnS₂ phototransistor. The results suggest that the method of reducing Shottky barrier width to achieve high mobility and photoresponsivity is effective, and Sb-doped SnS₂ monolayer has significant potential in future nanoelectronic and optoelectronic applications.