Tunneling experiments on amorphous and crystalline superconducting tantalum films

The energy gap and the transition temperature of amorphous and crystalline superconducting Ta films are measured by tunneling experiments. The following values are obtained: 2Δ(0) = 0.65 meV, Tsub(c) = 2.11 K for the amorphous state after quenched condensation and 2Δ(0) = 1.24 meV, Tsub(c) = 4.06 K for the crystalline state after annealing at room temperature. The reduced energy gap 2Δ(0)/kTsub(c) = 3.58 demonstrates that amorphous Ta films are weak-coupling superconductors. The crystallization of the amorphous Ta films takes place at 250 K. (orig.)