Selective thermalization in sputtering to produce high T<inf>c</inf>films

To understand the sputtering process as a means of producing high Tcmetastable superconducting compounds we have investigated the need for thermalization of the sputtered atoms as they are deposited on the substrate. We have used low pressure RF sputtering to produce Nb3Ge with Tcof ∼ 22°K for pressures of 20 mtorr Kr and for 45 mtorr Ar. To test the hypothesis that a thermalization is required to effect a high Tcin Nb3Ge we have been studying the sputtering process for systems such as Nb3Al where Kr is used to thermalize the Nb atoms with the minimum number of collisions and an admixture of Ne is used to optimally thermalize the Al atoms. A computer simulation of the sputtering process aids in the choice of optimum parameters. If the thermalization hypothesis is correct then co-evaporation should be able to produce high TcNb3Ge.