Growth and characterization of superconducting V3Si on Si and Al2O3 by molecular beam epitaxial techniques |
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Authors: | E T Croke R J Hauenstein C W Nieh T C McGill |
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Affiliation: | (1) California Institute of Technology Pasadena, 91125, California;(2) Present address: Hughes Research Laboratories, 90265 Malibu, CA |
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Abstract: | A study of the growth parameters governing the nucleation of metastable superconducting A15 V3Si on Si and A12O3 is presented. Nominally, 500Å films of V1-xSix were produced through codeposition of V and Si onto heated (111) Si and (1102) A12O3 substrates. Samples were prepared in a custom-built ultrahigh vacuum (UHV) chamber containing dual e-beam evaporation sources and a high temperature substrate heater. V and Si fluxes were adjusted to result in the desired average film composition. V0.75Si0.25 films prepared at temperatures in excess of 550° C on Si show significant reaction with the substrate and are nonsuperconducting while similar films grown on A12O3 exhibit superconducting transition temperatures(@#@ Tc @#@) approaching bulk values for V3Si (16.6-17.1 K). Codeposition at temperatures between 350 and 550° C results in superconducting films on Si substrates while growth at lower temperatures results in nonsuperconducting films. Lowering the growth temperature to 400° C has been shown throughex situ transmission electron microscopy (TEM) and Auger compositional profiling to minimize the reaction with the Si substrate while still activating the surface migration processes needed to nucleate A15 V3Si. Variation of film composition aboutx = 0.25 is shown to result in nonsuperconducting films for highx and superconducting films with Tc approaching the bulk V value (5.4 K) for lowx. Finally, lowering the V0.75Si0.25 deposition rate is shown to raise Tc. |
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Keywords: | Suicide Superconductor V3Si Codeposition Epitaxy UHV MBE |
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