The a-plane MgxZn1-xO (0 <= x <= 0.3) films were grown on r-plane (0 1 -1 2) sapphire substrates using metal-organic chemical vapor deposition (MOCVD). Growth was done at temperatures from 450 °C to 500 °C, with a typical growth rate of ~500 nm/h. Field emission scanning electron microscopy (FESEM) images show that the films are smooth and dense. X-ray diffraction (XRD) scans confirm good crystallinity of the films. The interface of MgxZn1-xO films with r-sapphire was found to be semicoherent as characterized by high-resolution transmission electron microscopy (HRTEM). The MgxZn1-xO surfaces were characterized using scanning tunneling microscopy (STM) in ultrahigh vacuum (UHV). Low-energy electron diffraction (LEED) shows well-ordered and single-crystalline surfaces. The films have a characteristic wavelike surface morphology with needle-shaped domains running predominantly along the crystallographic c-direction. Photoluminescence (PL) measurements show a strong near-band-edge emission without observable deep level emission, indicating a low defect concentration. In-plane optical anisotropic transmission was observed by polarized transmission measurements.
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