Effect of substrate microstructure on the misorientation of a-plane ZnO film investigated using x-ray diffraction

(11 (2) over bar0) ZnO (nonpolar a-plane ZnO) films were grown on (1 (1) over bar 02) Al(2)O(3) (r-plane sapphire) substrates by single-source chemical vapor deposition. The misorientation in the film was investigated in detail using x-ray diffraction techniques, including 2 theta-omega scan, reciprocal space mapping (RSM), and double- and triple-crystal x-ray diffraction analysis. 2 theta-omega scan and RSM measurements suggest that ZnO film grows on r-plane sapphire substrate epitaxially along the [11 (2) over bar0] orientation, and the (11 (2) over bar0) plane of the ZnO film tilts with respect to the (1 (1) over bar 02) plane of the substrate. RSM measurement for sapphire substrate shows that the diffraction intensity distribution around (2 (2) over bar 04) reciprocal lattice point presents a curved band along the 2 theta-omega scan direction, which can be attributed to a strained layer (or a lattice distortion layer) at the substrate surface. Double-and triple-crystal x-ray diffraction measurements imply that anisotropic mosaic exists in sapphire substrate. The strained layer and tilt mosaic in sapphire substrate may be the important reasons for the tilted growth of the (11 (2) over bar0) plane of a-plane ZnO film relative to (1 (1) over bar 02) plane of the Al(2)O(3) substrate. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3573670]