Deposition of Nb3Ge films on continuous stainless steel tapes by hollow cathode magnetron sputtering

A hollow cathode type of magnetron sputtering apparatus useful for coating a long wire with thin films at high deposition rate above 5000 Å/min and low applied sputtering voltage leads to a reduced energy of the sputtered atoms condensing on the substrate. Therefore, this sputtering apparatus seemed to be useful for depositing the high Tc films with a metastable A15 phase. Then, the deposition of Nb3Ge films on a continuous stainless steel tape has been attempted by using this sputtering apparatus. The target is a cylinder which is composed of a Nb tube with Nb end plates and Ge chips. The authors have succeeded in depositing the single A15 phase Nb3Ge films uniform in composition all over the tape substrate under the condition of applied voltage below 300 V and argon pressure above 10 mTorr. The deposited films exhibit relatively high Tc about 17 K.