Crystallographic structure and superconductive properties of Nb-Ti films with an artificially layered structure

Journal Article · Fri Jun 15 00:00:00 EDT 1990 · Journal of Applied Physics; (USA)

DOI:https://doi.org/10.1063/1.345809· OSTI ID:6787709

Sato, N ^[1]

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1. SONY Corporation, Research Center, 7-35 Kitashinagawa-6, Shinagawa-ku, Tokyo 141, Japan (JP)

Artificially layered niobium-titanium (Nb-Ti) films with various thickness ratios (3/1--1/3) and periodicities (2--100 A) are made in an argon or in a mixed argon/nitrogen atmosphere by a dc magnetron sputtering method. Films with small periodicities (less than 30 A) have an artificial superlattice structure (ASL) with crystallographic coherence between constituent layers, where Nb and Ti grow epitaxially on the closest planes. The crystallographic structures of films are bcc with the (110) plane parallel to the film for films with the same or a thicker Nb layer than a Ti layer, and hcp with the (001) plane parallel to the film for films with a thinner Nb layer than a Ti layer. Films with large periodicities have an artificial superstructure (ASS) with only periodic stacking of constituent layers. Films deposited in the Ar/N atmosphere also have the artificially layered structures of ASL or ASS. The artificially layered structure is thermally stable at temperatures up to 500 {degree}C. The superconducting properties of the films depend strongly on the periodicity and thickness ratio of Nb and Ti layers. The dependence of the transition temperature on the periodicity and thickness ratio is qualitatively explained by a proximity effect with a three-region model. Films with periodicities less than 20 A, composed of the same or a thicker Nb layer than a Ti layer, show high transition temperatures (above 9.3 K). The highest {ital T}{sub {ital c}} of about 13.6 K is obtained in the film composed of monatomic layers of constituents deposited in an Ar atmosphere including 30 vol % N.

• OSTI ID: 6787709
• Journal Information: Journal of Applied Physics; (USA), Journal Name: Journal of Applied Physics; (USA) Vol. 67:12; ISSN 0021-8979; ISSN JAPIA
• 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
BCC LATTICES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
EPITAXY
FILMS
HCP LATTICES
HEXAGONAL LATTICES
LAYERS
METALS
NIOBIUM
PHYSICAL PROPERTIES
PROXIMITY EFFECT
SPUTTERING
SUPERCONDUCTIVITY
SUPERLATTICES
THERMODYNAMIC PROPERTIES
TITANIUM
TRANSITION ELEMENTS
TRANSITION TEMPERATURE