Dependence of magnetic penetration depth on the thickness of superconducting Nb thin films
A. I. Gubin, K. S. Il’in, S. A. Vitusevich, M. Siegel, N. Klein
DOI 10.1103/PhysRevB.72.064503 · Physical Review B
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Abstract
In this paper we present the results of a systematic study on the magnetic field penetration depth of superconducting niobium thin films. The films of thicknesses ranging from 8to300nm were deposited on a Si substrate by dc magnetron sputtering. The values of the penetration depth λ(0) were obtained from the measurements of the effective microwave surface impedance by employing a sapphire resonator technique. Additionally, for the films of thickness smaller than 20nm, the absolute values of λ(0) were determined by a microwave transmission method. We found that the reduction of the film thickness below 50nm leads to a significant increase of the magnetic field penetration depth from about 80nm for 300nm thick film up to 230nm for a 8nm thick film. The dependence of the penetration depth on film thickness is described well by taking into account the experimental dependences of the critical temperature and residual resistivity on the thickness of the niobium films. Structural disordering of the films and suppression of superconductivity due to the proximity effect are considered as mechanisms responsible for the increase of the penetration depth in ultrathin films.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 9.7 | Pressure not reported | midpoint |
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