The Superconducting Transition in Boron Doped Silicon Films

T. Kociniewskia, b, D. Débarrea, b, A. Grockowiakc, d, J. Kačmarčíkc, e, C. Marcenatc, E. Bustarretd, L. Ortegad, T. Kleind, f, G. Prudong, C. Duboisg, B. Gautierg and J.C. Dupuyg aUniversité Paris-Sud, Institut d'Electronique Fondamentale, UMR8622, 91405 Orsay, France bCNRS, 91405 Orsay, France cCEA-INAC/UJF-Grenoble 1, SPSMS, UMR-E 9001, 17 Rue des Martyrs, 38054 Grenoble, France dCNRS, Institut Néel, B.P. 166, 38042 Grenoble, France eCentre of Very Low Temperature Physics, IEP SAS and FS UPJŠ, 040 01 Košice, Slovakia fInstitut Universitaire de France and Université Joseph Fourier, B.P. 53, 38041 Grenoble, France gCNRS and INSA, Institut des Nanotechnologies de Lyon, 7 av. J. Capelle, 69621 Villeurbanne, France

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We report on a detailed analysis of the superconducting properties of boron-doped silicon films grown along the 001 direction by gas immersion laser doping. This technique is proved to be a powerful technique to dope silicon in the alloying range 2-10 at.% where superconductivity occurs. The superconducting transitions are sharp and well defined both in resistivity and magnetic susceptibility. The variation of Tc on the boron concentration is in contradiction with a classical exponential dependence on superconducting parameters. Electrical measurements were performed in magnetic field on the sample with cB = 8 at.% (400 laser shots) which has the highest Tc (0.6 K). No hysteresis was found for the transitions in magnetic field, which is characteristic of a type-II superconductor. The corresponding upper critical field was on the order of 1000 G at low temperatures, much smaller than the value previously reported. The temperature dependence of Hc2 is very well reproduced by the linearized Gorkov equations neglecting spin effects in the very dirty limit. These measurements in magnetic field allow an estimation of the electronic mean-free path, the coherence length, and the London penetration depth within a simple two-band free electron model.

DOI: 10.12693/APhysPolA.118.1026 PACS numbers: 74.62.Dh, 73.61.Cw, 74.70.Ad