Investigations of the energy gap of V3Si monocrystals

On the surface of single phase V3Si single crystals, tunnel junctions with reproducible and stable characteristics are prepared by an anodic oxidation method for the barrier preparation and by Pb and In top electrodes. Detailed energy gap investigations yield Δ0 = (2.52 +- 0.05) meV for V3Si. Based on this energy gap value the evaluation of the ratio 2Δ0/kTsub(c) is discussed and conclusions about the strength of electron-phonon interaction in V3Si are given. The temperature dependence of the energy gap obtained by measurements in the temperature range 1.5 K <= T <= 20 K can be described by the relation Δ(T)/Δ0 = tanh [Tsub(c)Δ(T)/TΔ0]. In order to exclude measuring errors, a numerical evaluation of the Δ(T) values is provided resulting in a Tsub(c)-lowering in the surface range. Furtheron, at T = 1.5 K, the measurements show an additional gap structure, the cause of which is discussed. Investigations of the tunnel characteristics measured in different crystallographic orientations do'nt yield any measurable anisotropy of the energy gap. (author)