Superconducting transition temperatures of two-dimensional ultrathin V films and quasi-two-dimensional V-Si multilayered systems

K. Kanoda; H. Mazaki; T. Mizutani; N. Hosoito; T. Shinjo

doi:10.1103/PhysRevB.40.4321

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Superconducting transition temperatures of two-dimensional ultrathin V films and quasi-two-dimensional V-Si multilayered systems

K. Kanoda, H. Mazaki, T. Mizutani, N. Hosoito, T. Shinjo

DOI 10.1103/PhysRevB.40.4321 · Physical Review B

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Abstract

Ultrathin V films (down to the thickness of 25 Å) and V-Si multilayered substances were successfully prepared by ultrahigh-vacuum electron-beam evaporation and were investigated with resistive measurements. The superconducting-transition width was 20–30 mK for all the samples. The transition temperature Tc of V films decreases with a decrease in the thickness. We found that in the thicker films this is mainly due to the electron lifetime effect on the density of states (the bulk resistivity effect), but in the thinner films (with larger sheet resistances) the localization and/or interaction effects are essential. Meanwhile, Tc of the V-Si systems exhibits a particular dependence on the Si-layer thickness. As the thickness increases, Tc decreases linearly up to a certain threshold thickness and then keeps a constant value equal to that of an isolated V film. The result is discussed in the context of a crossover of electron-localization dimensionality.