Superconductive properties of amorphous molybdenum-germanium alloys

Thesis/Dissertation · Sat Jan 01 04:00:00 EST 1983

OSTI ID:6536069

Carter, W L

High quality amorphous molybdenum-germanium films have been synthesized by magnetron sputtering and electron-beam co-evaporation. The films are found to be amorphous for germanium concentrations greater than about 20 to 25 atomic percent, depending on deposition conditions. The superconductive properties of the films were studied by tunneling, upper critical field, heat capacity and critical current measurements. The tunnel junctions lacked the necessary high bias properties to enable a determination of the electron-phonon coupling spectrum but had a ratio of energy gap to transition temperature characteristic of BCS-like superconductors in agreement with other amorphous transition metal alloys. Measurements of the upper critical field could be fit by the Werthamer-Halfand-Hohenberg-Maki theory but required unphysically short spin-orbit scattering times to achieve a convincing fit. Measurements of the specific heat of 350 microgram samples gave values of the density of states in only marginal agreement with those determined from critical field measurements and confirmed the weak-coupled nature of the alloys. The results were interpreted in terms of the non-orthogonal tight-binding calculations of Varma and Dynes and found to be in reasonable agreement for high germanium concentrations but possibly deviating at concentrations below 30 atomic percent germanium. Measurements of the critical current density indicate that two pinning mechanisms exist in the as-synthesized films, one at low fields and one at high fields, but neither mechanisms has been identified.

• OSTI ID: 6536069
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
AMORPHOUS STATE
CRITICAL CURRENT
CRITICAL FIELD
CURRENTS
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRICAL PROPERTIES
GERMANIUM ALLOYS
JUNCTIONS
MAGNETIC FIELDS
MEASURING METHODS
MOLYBDENUM ALLOYS
PHYSICAL PROPERTIES
SPECIFIC HEAT
SUPERCONDUCTING JUNCTIONS
SUPERCONDUCTIVITY
THERMODYNAMIC PROPERTIES