Epitaxial growth of ZnO thin films on AlN substrates deposited at low temperature by magnetron sputtering

Hexagonal aluminium nitride (AlN) and zinc oxide (ZnO) thin films have been deposited by DC and RF reactive magnetron sputtering at room temperature. For a first set of samples, sputtered AlN films were deposited on silicon ZnO substrate. For a second set, ZnO films were deposited on AlN substrate. Xray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analysis of the synthesized AlN film on ZnO buffer layer have shown some amorphous zones close to the interface followed by a nanocrystalline layer exhibiting (10-10) and (0002) orientations of the hexagonal AlN crystalline phase. At the top of the film, a relatively well-crystallized layer with a single (0002) orientation has been observed. We have related the relatively bad interface to the presence of oxygen coming from ZnO substrate. This behaviour was different for the growth of ZnO film when AlN was used as substrate. In fact, we have observed thanks to HRTEM images and selected area electron diffraction patterns, that the ZnO film deposited on AlN substrate exhibits an epitaxial growth which is strongly dependent on the crystalline quality of AlN film. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim