Superconductivity in Nb/Cu superlattices

Thesis/Dissertation · Fri Jan 01 00:00:00 EST 1982

OSTI ID:6859150

Banerjee, I

Superconducting samples of equal layer thickness have been made by sequential deposition of Nb and Cu on single crystal sapphire substrates. The individual layer thicknesses were varied from 5-5000, the total thickness of each sample being kept equal to approx.1..mu..m. Both materials grow preferentially perpendicular to the substrate - Cu(111) and Nb(110). Layer thicknesses were determined from the relative position of the superlattice peaks of the Bragg x-ray spectrum of the sample. These results agreed well with the layer thickness determined from the geometric parameters of the system. The superconducting transition temperature T/sub c/ of the Nb/Cu superlattices has been investigated as a function of layer thickness. The dependence of T/sub c/ above 300 layer thickness agrees well with the proximity effect theory with no adjustable parameters. Below 300, the data in conjunction with the proximity effect theory shows that T/sub c/ of Nb decreases with layer thickness. This is interpreted in terms of a change in the electronic density of states due to a decrease in the mean free path. The temperature and angular dependence of the critical fields of the above mentioned samples have also been studied. For layer thickness between 100 and 300, evidence for dimensional crossover has been observed in the temperature dependence. Associated with the crossover the author finds a change in the angular dependence given by the effective mass theory. This is the first time that a relationship has been observed between dimensional crossover in the temperature dependence and a change in the angular dependence of critical fields.

• OSTI ID: 6859150
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COPPER
SUPERCONDUCTIVITY
NIOBIUM
CRITICAL FIELD
CRYSTAL GROWTH
CRYSTAL LATTICES
EXPERIMENTAL DATA
FABRICATION
LAYERS
SAPPHIRE
SUBSTRATES
TEMPERATURE DEPENDENCE
THICKNESS
TRANSITION TEMPERATURE
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CORUNDUM
CRYSTAL STRUCTURE
DATA
DIMENSIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
INFORMATION
MAGNETIC FIELDS
METALS
MINERALS
NUMERICAL DATA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
360104* - Metals & Alloys- Physical Properties
656102 - Solid State Physics- Superconductivity- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena- (-1987)