Specific heat of thin-film A15 superconductors: An anomalous inhomogeneity discovered

Journal Article · Wed Jul 01 04:00:00 EDT 1987 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.36.107· OSTI ID:5818023

Hellman, F; Geballe, T H

Thin films of metallurgically stable A15 superconductors, primarily Nb-Sn, V-Ga, and V-Si, have been prepared by electron-beam coevaporation onto heated sapphire substrates. The specific heat of these films at low temperature reveals that the width of the transition from the normal to the superconducting state varies from a low of 0.3 K for stoichiometric Nb/sub 3/Sn to a high of 6 K for A15 Nb-Sn prepared off-stoichiometry. The systematics of this transition width were probed by varying the deposition parameters. A strong dependence is found on deposition temperature, composition, and microstructure. The source appears to be a compositional inhomogeneity which develops at the film surface during growth. A model is proposed for a new type of surface segregation applicable in a growing film where the surface mobility is orders of magnitude greater than the bulk mobility.

• Research Organization: Department of Applied Physics, Stanford University, Stanford, California 94305
• OSTI ID: 5818023
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 36:1; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
BETA-W LATTICES
COHERENCE LENGTH
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIMENSIONS
FILMS
GALLIUM ALLOYS
LENGTH
NIOBIUM ALLOYS
PHYSICAL PROPERTIES
SAMPLE PREPARATION
SEGREGATION
SILICON ALLOYS
SPECIFIC HEAT
SUBSTRATES
SUPERCONDUCTING FILMS
THERMODYNAMIC PROPERTIES
TIN ALLOYS
TRANSITION TEMPERATURE
VANADIUM ALLOYS