Anisotropic microstructure of hydrothermally-grown non-polar a-plane ZnO on a-plane GaN film

초록

Nonpolar a-plane ZnO (a-ZnO) films with good crystalline quality have been achieved by a hydrothermal growth method on nonpolar a-plane GaN (a-GaN) films without any nucleation steps. The X-ray diffraction theta-2 theta scan of the a-ZnO film grown on a-GaN film showed that the film was uniformly a-plane (11 (2) over bar0) oriented. The a-ZnO films exhibited anisotropic peak broadenings of the on-axis rocking curves with X-ray in-beam orientations. The full width at half maximum of the on-axis rocking curve of nonpolar a-ZnO film along the c-axis direction was measured to be 2092 arc sec, which is almost two times larger than the one along the m-axis direction (1219 arc sec). The Williamson-Hall plot analysis of the symmetric (11 (2) over bar0) and (22 (4) over bar0) Bragg reflections showed that the mosaic tilt values were 0.647 degrees and 0.407 degrees along the c-axis and m-axis directions, respectively. It clearly indicates that large mosaic tilt along the c-axis in a-ZnO film is mainly responsible for the anisotropic peak broadenings of the on-axis rocking curves with respect to X-ray in-beam orientations. (C) 2014 Elsevier B.V. All rights reserved.

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