Growth of high-quality epitaxial ZnO films on α-Al₂O₃

ZnO epitaxial thin films have been grown on sapphire(0 0 0 1) substrates by molecular beam epitaxy using elemental zinc and oxygen supplied by an RF radical source. Despite the large lattice mismatch between ZnO and the underlying sapphire substrate, ZnO layers with (0 0 0 2) rocking curve half-widths of approximately 12 arcsec have been grown. X-ray reciprocal lattice scans along the [0 0 0 1] direction show strong Pendellosung fringes indicating the presence of an extremely flat interface and surface as was confirmed by atomic force microscopy experiments. X-ray pole figure measurements indicate that the a-axis of the epilayer was rotated with respect to the a-axis of the substrate by 30°. Preliminary photoluminescence measurements indicate predominant near-bandedge emission.