Superconducting transitions in amorphous molybdenum-germanium ultrathin films and multilayers

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5163940

Missert, N

The primary goal of this work was to clarify the role of enhanced Coulomb interactions in the destruction of superconductivity in disordered systems of reduced dimensions. Through a systematic study of the critical temperatures in single film sandwich and multilayer structures, the author has examined the role of dimensionality in the reduction of {Tc} in disordered superconductors. The author has observed a continuous crossover from two to three dimensional behavior as electron diffusion between individual superconducting layers in the multilayer becomes possible. This demonstrates unambiguously that the reduction in {Tc} is an artistic 2D effect and is not simply due to interface or proximity effects, as has often been assumed in the past. Multilayers were fabricated by sequential cosputtering of alternate layers of superconducting and nonsuperconducting amorphous Mo-Ge alloys. The effects of screening at short length scales in these films are probed via a systematic variation of both the distance between superconducting layers and the conductivity of the nonsuperconducting layers in a multilayer structure. As the conductivity of the nonsuperconducting layer increases, electron diffusion becomes more three dimensional. However this increased conductivity also introduces a reduction in {Tc} due to the proximity effect. This has been accounted for by comparing the T, of the multilayers with a corresponding NISIN single layer sandwich structure, designed to have an identical proximity effect reduction of {Tc}, in addition to compensating for any effect of the SIN interface itself. X-ray diffraction measurements and cross-sectional TEM micrographs confirm that the layers are structurally well defined, uniform, and continuous.

• Research Organization: Stanford Univ., CA (United States)
• OSTI ID: 5163940
• 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
BCS THEORY
COHERENT SCATTERING
COMPOSITE MATERIALS
DIFFRACTION
DIFFUSION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRONS
ELEMENTARY PARTICLES
FABRICATION
FERMIONS
FILMS
GERMANIUM ALLOYS
KOSTERLITZ-THOULESS THEORY
LAYERS
LEPTONS
MATERIALS
MOLYBDENUM ALLOYS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
SCATTERING
SUPERCONDUCTING COMPOSITES
SUPERCONDUCTING FILMS
SUPERCONDUCTIVITY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
THIN FILMS
TRANSITION TEMPERATURE
X-RAY DIFFRACTION