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.