Homo-buffer layer effects and single crystalline ZnO hetero-epitaxy on c-plane sapphire by a conventional RF magnetron sputtering

In this article, it is shown that high quality single crystalline ZnO films could be successfully grown on c-plane sapphire by a conventional RF magnetron sputtering. High-resolution X-ray diffractometry, transmission electron microscopy (TEM), scanning electron microscopy, and low-temperature photoluminescence investigations clearly confirmed that the ZnO films grown on Al2O3(0001) at substrate temperatures above 650degreesC were high quality single crystal, showing the full-width at half-maximum of (0002) rocking curve as narrow as 0.03degrees, symmetric six poles in pole figure, sharply defined hexagonal spot pattern in plan-view TEM diffraction diagram, extremely flat surface with a roughness below 0.2 nm, and exciton emission peak width as narrow as 7 meV. It was also found that an introduction of homo-buffer pre-grown at 500degreesC can induce a homogeneous interface and an improved emission characteristic by relaxing the compressive strain caused by large lattice and thermal mismatch between the film and substrate and by reducing defect density in interface region. (C) 2004 Elsevier B.V. All rights reserved.