Energy gaps of ordered and disordered A15 ’’phases’’ in Nb3Ge measured by tunneling

Abstract

In electron tunneling measurements into high-Tc getter-sputtered Nb3Ge films, two energy gaps are clearly identified. The larger, 2Δ=7.8 meV, we associate with well-ordered A15 material. The smaller, 2Δ∼1.0 meV, we suggest indicates the presence of very disordered material, because we cannot identify any known phase of the NbGe system with this low gap, and because a most interesting ’’phase’’ of Nb3Ge, with 2Δ=0.86 meV and Tc=3.06 K, was isolated by sputtering from the same target onto a cold (100−200 °C) substrate.