Superconducting properties of B1 nitrides film obtained by gas-metal reaction for RF application

The authors investigated the RF behavior of the B1-type superconductors NbN obtained by reacting reactor-grade niobium samples in high-purity (10 p.p.m. of total impurities) nitrogen atmosphere after a baking at high temperature (800 degrees C) in an UHV furnace. They obtained a critical temperature of 14.6 K for a tetragonally distorted cubic lattice with cell parameters a=4.381 AA and c=4.324 AA, as determined by X-ray diffraction. The RF test showed for the resonator, operating at 4.5 GHz, a surface resistance at 4.2 K of 1 mu Omega in good agreement with the value predicted by the BCS theory.<
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