Sputtering of high TcNb3Ge and Nb3Si

We present observations of two effects that relate to the formation of high TcNb3Ge and Nb3Si A15 phases using a DC getter sputtering technique. The first is an effect associated with convection of the sputtering gas which has been studied by tilting of sample substrates and heater with respect to the horizontal. The second effect is associated with surface markings on the films, in particular in the Nb-Si system. These observations constitute further evidence of the complexity of this sputtering process and indicate that unless there is careful control of the experimental conditions, the deposition parameters and the film properties are likely to vary locally on a rather small scale. Finally we shall discuss some of the reservations we have concerning the high Tcvalues we observe in the Nb-Si system.