Columnar microstructure of the ZnO shell layer deposited on the GaP nanowires

Abstract We studied properties of a columnar structure of ZnO shell layers deposited on GaP nanowires. Detailed TEM observation showed that the ZnO shells consist of a multilayered system of ZnO nanocrystallites (grains). This morphology was observed also for the shells as thin as 10 nm. The longitudinal TEM analysis showed that ZnO deposited on the GaP NWs has a columnar morphology. The columns are inclined at a positive angle close to 70° with respect to the GaP core axis; all columns observed were tilted at this angle to the growth direction. Although we did not observe ZnO columns tilted at 109.5° (negative angle) to the growth direction, this possibility cannot be excluded at this stage. We tentatively conclude that ZnO nanocrystallites grew preferentially on the {1 1 1}A facets of the GaP NWs. The polycrystalline character of the ZnO layer, inferred from the TEM images, was confirmed by the XRD pattern. The size of the crystallites evaluated from XRD measurements (application of Scherrer's formula) agreed with their size observed by TEM.