The chemical reactivity of thin layers (ca. 10nm thick) of ZnO deposited onto differently oriented Al2O3 single crystals has been investigated by means of atomic force microscopy inspections and X-ray absorption spectroscopy at the Zn–K edge. The (0001) ZnO∥(112¯ 0) sapphire interface yields the ZnAl2O4 spinel and a quite stable film morphology. Instead, the (112¯ 0) ZnO∥(11¯ 02) sapphire and (0001) ZnO∥(0001) sapphire interfaces give origin to a new compound (or, possibly, even two new compounds), whose chemical nature is most ...