Superconducting properties of an NbN–SiO2 disordered system obtained by ammonolysis of NbN–SiO2 sol–gel derived coatings

Studies in superconducting properties of NbN–SiO2 films are reported. The films were obtained through nitridation of sol–gel derived Nb2O5–SiO2 coatings at 1200 °C, a process leading to the formation of disordered structures with NbN metallic grains dispersed in the insulating SiO2 matrix. Electrical resistivity was measured with the conventional four-terminal method in the temperature range from 5 to 280 K. The samples’ superconducting properties, examined with magnetically modulated microwave absorption (MMMA), depend on the NbN/SiO2 molar ratio and the film’s thickness.