The penetration depth of an electromagnetic field in superconducting niobium nitride films

For granular NbN films, the electromagnetic field penetration depths have been determined from the temperature dependence of the resonance microwave frequency of microstrip resonators made of niobium nitride. The experimental results are analyzed in terms of the Ambegaokar-Baratoff theory. Expressions are obtained which relate the field penetration depth to the specific resistance and Tc of thin NbN films.