Effects of a low-temperature sulfidation process on the microstructural properties of ZnO nanowires: ZnS formation and nanoscale Kirkendall effect

Abstract

We report on the microstructural characterization of ZnO nanowires during a low-temperature sulfidation process. The morphology of ZnO-ZnS core-shell nanowires obtained for different reaction times was observed. After sulfidation, two different interfaces were observed between the crystalline ZnO core and nanostructured ZnS shell. One is flat {10 (1) over bar0} planes covered with a dense ZnS NP layer and the other is rough {10 (1) over bar0} planes covered with two porous layers of ZnO and ZnS NPs. Voids were formed inside the crystalline ZnO core, resulting in Kirkendall voids with a hexagonal shape and six symmetrically located {10 (1) over bar0} planes, which have lower surface energy compared to {11 (2) over bar0}. It is believed that these Kirkendall voids are considerably affected by surface energy.