Layered superconducting composites

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1981

OSTI ID:5197324

Ruggiero, S T

Finely layered Niobium/Germanium composites with unique physical and superconducting properties are discussed. These materials are studied as model systems for quasi-two-dimensional superconductors and have provided quantitative verification of dimensional crossover behavior in complete agreement with the Josephson-coupling theory. The composites consist of alternating sputter-deposited thin films of Nb and Ge. Individual layer thickness ranges from 5 A to 100 A; typical samples contain 50 Nb/Ge layer pairs of fixed thickness ratio. We have investigated the structural and transport properties of the composites as a function of layer thickness. Likewise the critical temperature and normal-state properties, including the heat capacity and density of states (inferred from critical field measurements), have been studied. Measurements have been made of the parallel upper critical fields below T/sub c/ and the fluctuation conductivity above T/sub c/ of samples with selected Ge thicknesses. These results have revealed a systematic variation in the dimensional nature of these systems both with Ge layer thickness and, in the quasi-2D systems, temperature. Systematic behavior in anomalous positive curvature of the perpendicular upper critical fields has been examined and discussed in the context of a possible manifestation of 2D vortex-lattice melting.

• Research Organization: Stanford Univ., CA (USA)
• OSTI ID: 5197324
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360304* -- Composite Materials-- Physical Properties-- (-1987)
COMPOSITE MATERIALS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
GERMANIUM
LAYERS
MATERIALS
METALS
NIOBIUM
PHYSICAL PROPERTIES
SPECIFIC HEAT
SPUTTERING
SUPERCONDUCTIVITY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS