A grazing incidence x-ray diffraction with a synchrotron radiation and a cross-sectional high-resolution transmission electron microscopy were performed on the sapphire surface nitrided at 1080 degrees C for 30 min. The thickness of the nitrided layer was about 2 nm. It was found out that the wurtzite, zinc-blende, and 30 degrees rotated zinc-blende aluminum nitrides were formed on the sapphire surface. The 30 degrees rotated zb-AlN formed the incoherent interface and has higher activation energy of formation, while the nonrotated zb-AlN formed the coherent interface. (c) 2007 American Institute of Physics.