Growth and Surface Characterization of a Type-II ZnO/ZnS Heterostructure

We report the in situ formation of a type-II ZnO/ZnS heterostructure via the thermal oxidation of a ZnS(001) single crystal under a clean controlled oxygen atmosphere. By combining X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), we investigated the chemical composition, electronic structure, and surface morphology of the resulting interface. Core-level shifts observed in our XPS measurements suggest an upward band-bending due to the formation of a hybrid interface. AFM measurements show that ZnO grows through a layer-plus-island mode, forming distorted hexagonal nanoislands. Our band alignment analysis confirms the type-II heterostructure arrangement with suitable electronic band-edge positions for efficient charge separation, highlighting its potential as a platform for photocatalytic applications, such as hydrogen and oxygen evolution reactions (HER and OER).