Morphology evolution of a-plane ZnO films on r-plane sapphire with growth by pulsed laser deposition

▸ Distinct evolution of surface morphologies for a-plane ZnO grown on r-plane sapphire at low and high temperatures is reported. ▸ (1 × 2) reconstruction occurs with step-flow growth was observed for ZnO grown at 750 °C (HT-ZnO). ▸ ZnO grown at 450 °C (LT-ZnO) shows island growth mode for initial growth. ▸ Significant change of surface morphology while cooling process had been observed by in situ RHEED. ▸ Both HT- and LT-ZnO films evolve into stripe morphology for thick film. (>100 nm).