Magnetic Penetration Depths and Normal-State Resistivities of Epitaxial and Polycrystalline NbCxN1-x Films

We have studied the magnetic penetration depth λ and the normal-state resistivity ρ of epitaxial and polycrystalline NbCxN1-x films as a function of film thickness t and sputtering gas pressure P during the deposition of the films. It was found that λ(~200 nm) and ρ(~50 µΩcm) of epitaxial films are almost independent of P and t, while λ(>300 nm) and ρ(>110 µΩcm) of polycrystalline films increase considerably with increasing P(>2 Pa) or decreasing t(<80 nm). The pressure and thickness dependence of λ and ρ of polycrystalline films can be explained by a model of Josephson coupling between grains.