Niobium nitride thin films deposited by high temperature chemical vapor deposition

Synthesis of thin niobium nitride (NbN) layers by High Temperature Chemical Vapor Deposition (HTCVD) is presented and the crystallographic orientations are investigated during heteroepitaxial growth on (0001)Al2O3, (0001)AlN template and 112¯0Al2O3. The HTCVD NbN layers are ex-situ characterized by means of X-ray diffraction (XRD) methods, Raman spectroscopy and Transmission Electron Microscopy (TEM). Depending on the deposition temperature, hexagonal NbN or fcc (face-centered cubic) δ-NbN is obtained. Orientation relationships between the fcc δ-NbN layer with respect to the substrates are given. We discuss the role of an AlN layer as a possible protective layer of the sapphire for the synthesis of fcc δ-NbN.