Low frequency noise in freely suspended tin films at the superconducting transition. [Spectral density]

Conference · Fri Jul 01 04:00:00 EDT 1977

OSTI ID:5349787

Ketchen, M B; Clarke, J

The spectral density, S/sub v/(f), of the voltage noise across 1-D current-biased tin films has been measured at the superconducting transition. Each film was freely suspended between two thermal clamps a distance L apart in a vacuum can. A thin layer of lead was evaporated on the outer portion of the films to leave an uncoated middle region of length l. S/sub v/(f) was flat at frequencies below f/sub L/ approximately D/L/sup 2/, where D is the thermal diffusivity. At frequencies between f/sub L/ and f/sub l/ approximately (L/l)/sup 2/f/sub L/ the slope was typically -0.8, while at frequencies above f/sub l/ the slope was somewhat less steep than -1.5. The shape and magnitude of S/sub v/(f) were in good agreement with an equilibrium temperature fluctuation model in which the temperature fluctuations are spatially uncorrelated. Measurements of the autocorrelation function also strongly supported this model. These results are in contrast with those obtained for normal films and films at the superconducting transition supported by substrates, for which a model was required with spatially correlated fluctuations. It is concluded that the 1/f noise for films on substrates is mediated by an interaction between the substrate and the film.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5349787
• Report Number(s): LBL-6631; CONF-770750-1
• 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
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
FILMS
FLUCTUATIONS
FUNCTIONS
LEAD
METALS
NOISE
PHYSICAL PROPERTIES
SPECTRAL DENSITY
SPECTRAL FUNCTIONS
SUPERCONDUCTING FILMS
SUPERCONDUCTIVITY
TIN
VARIATIONS