We have previously employed an AlN buffer layer to facilitate epitaxial growth of sp 2 -BN on c-cut sapphire. AlN growth on r-cut Al2O3 also showed a-plane (1120) oriented growth suggesting growth orientations can be altered based on the substrate used. Other studies of AlN growth on c-cut and a-cut Al2O3 showed that the growth direction was identical in both cuts of Al2O3. This is relevant since the surface nitridation of Al2O3 is observed and expected for thermal CVD at such high temperatures.