| The goal of this thesis work was to prepare homogeneous films of niobium germanium (Nb(,3)Ge) with a high superconducting transition temperature (T(,c)) in order to study the physics of high-T(,c) superconductivity as well as to investigate potential technological uses.; By carefully controlling temperature homogeneity during preparation of the Nb(,3)Ge samples, we have prepared homogeneous films of high-T(,c) Nb(,3)Ge. Homogeneity is demonstrated by a sharp transition width ((DELTA)T(,c) . Thus (lamda) increases with T(,c) while decreases in agreement with the idea that mode softening is a major factor in the increase of T(,c) with approach to stoichiometry as previously found in Nb(,3)Al by Kwo and Geballe. Theoretical functional derivatives for T(,c) (by Bergmann and Rainer) and the energy gap (by Mitrovic et. al) qualitatively explain the rise in T(,c), energy gap and 2(DELTA)/K(,B)T(,c). Heat capacity, and critical field measurements have been performed to give bulk Nb(,3)Ge properties. (lamda) for this material is a moderate 34 (+OR-) 1.5 mJ/mole(DEGREES)K('2), thus there is no evidence for there being a high density of states in Nb(,3)Ge. Also, values for 2(DELTA)/k(,B)T(,c) = 4.2 (+OR-) .1 and (DELTA)C/(gamma)T(,c) = 1.87 indicate a strong coupled superconductor, as also seen by tunneling.; Homogeneous Nb(,3)Ge films have been made with high J(,c) demonstrating potential technological usefulness. Study of the physics involved suggests that mode softening is responsible for the high-T(,c) superconductivity in Nb(,3)Ge. |
