Nb Film Produced by D.C. Magnetron Sputtering in Liquid N_2 Vessel

Very pure Nb with good crystallinity thin films have been prepared readily by D.C. magnetron sputtering in a vessel containing liquid nitrogen whose outer wall constitutes a sputtering chamber. This was done while the Bell jar was completely separated from the pumping system with the main valve closed fully and the vessel was acting as a cryo-pump which was full of liquid nitrogen. The sputtering deposition rate of 3000 A/min. was observed and the superconducting and other physical properties of Nb thin films are discussed. The highest ratio (in Japan) of resistance at room temperature to that at 10 K, which shows the purity of metals, was obtained.