Structure and superconductivity of VN–SiO2 films obtained by thermal nitridation of sol–gel derived coatings

In this work studies of the structure and superconducting properties of xVN − (100 − x)SiO2 films (where x = 90, 80, 70 and 60 mol%) are reported. The films were obtained through thermal nitridation (ammonolysis) of sol–gel derived V2O3–SiO2 coatings (in a proper V2O3/SiO2 ratio) at 1200 °C. This process led to the formation of a disordered structure with VN metallic grains dispersed in the insulating SiO2 matrix. The structural transformations occurring in the films as a result of ammonolysis were studied using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The superconducting properties of the samples were examined with magnetically modulated microwave absorption (MMMA). All the samples apart from x = 90 exhibited superconducting transition above 6 K.