The preferential growth of ZnS on ZnOnanorods

Transmission and scanning electron microscopy are used to examine the sulphidation of hydrothermally grown [0001]-oriented ZnO nanorods in aqueous thioacetamide (CH3C(S)NH2) solution. At the early stages of growth, the reaction occurs preferentially on the (0001) top surface, confirmed to be Zn-polar by convergent beam electron diffraction, and on the lines of intersection of the {101¯0} facets. It is shown that the reaction involves surface migration of Zn species towards ZnS deposits. The presence of voids at the ZnS/ZnO interface also confirms a Kirkendall mechanism where ZnS grows from the top surface of the deposit.

Graphical abstractTEM image comparison of ZnS surface decoration on ZnO nanorod (a)after 15 min sulphidation shows a relatively uniform deposit on the (0001) end facet, (b) 30 min sulphidation shows a more extensive reaction on the (0001) facet which gives a mushroom-like appearance of the nanorod and (c) 60 min sulphidation shows the end cap partially detached and a voided region underneath. The presumed growth direction is arrowed (based on the lack of reaction at the other end). Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The mechanism of sulphide growth on (0001) ZnO nanorods is examined by TEM and SEM. ► The reaction occurs on (0001) and on the lines of intersection of the {101¯0}. ► The reaction involves Zn migration to reaction sites via surface diffusion. ► A voided interlayer between ZnS and ZnO may be explained by the Kirkendall effect.