Atomically stepped, pseudomorphic, corundum-phase (Al1-xGax)2O3 thin films (0 ≤ x < 0.08) grown on R-plane sapphire

Atomically smooth, pseudomorphic (Al1-xGax)(2)O-3 thin films were grown for 0 <= x < 0.08 on R-plane sapphire (01.2) by pulsed laser deposition at growth temperatures up to 1000 degrees C. Films up to 720 nm thickness show atomically stepped surfaces with monolayer terraces, similar to the substrates prior to growth, in wide ranges of growth pressure and temperature. A careful analysis of 13 symmetric, skew-symmetric, and asymmetric X-ray peaks agrees quite well with the continuum elastic strain theory of pseudomorphic distortion in corundum heterostructures by M. Grundmann [J. Appl. Phys. 124, 185302 (2018)]. The Ga-contents x and weak deviations from the expected ratios of rhombohedral c/a lattice constants are obtained from the best fits of the spacing of the (02.4), (04.8), and (00.6), (00.12) film and substrate reflections, in reasonable agreement with chemical energy dispersive X-ray spectrometry analyses. In addition, the measured tilts of the asymmetric film lattice planes corroborate the elastic theory. Published by AIP Publishing.