：Fabrication and Properties of Niobium Nitride Films by Reactive Sputtering at Ambient Substrate Temperature

NbN films of～0．1μm thickness have been prepared by reactive sputtering at ambient substrate temperature ， total gas pressure and Ar gas flow rate being kept constant ， and N2 gas flow rate being varied ． Measurements of superconducting temperature Tc and of electrical resistances at 300 K and 77K ， and X－ray diffraction analysis have been carried out ， The Tc and the lattice constant showed the maximums at a N2 gas flow rate ． The films were composed of BI structure with the less amoun