The influence of annealing and mechanical deformation on the superconductivity and structure of DC-sputtered Nb3Ge

The relationship of Tcto film composition, lattice parameter, ordering, and mechanical deformation in Nb3Ge has been investigated. Particular attention has been focused on annealing effects in these films, both those occurring during the deposition as well as post-fabrication effects. We find that inadequate time or temperature of annealing during or after deposition does not allow the maximum possible Tcfor a given composition to be obtained, while excessive annealing induces the precipitation of second phase Nb5Ge3with a concomitant decrease in Tc. The presence of second phase material accelerates the decrease of Tcwith annealing. Four-point bending measurements show Tc\´s of the films deposited on Al2O3substrates are unchanged up to strains . The breaking strain of these Al5-ceramic composites increases upon addition of a Au layer to the composite.