Energy gaps of the A-15 superconductors Nb/sub 3/Sn, V/sub 3/Si, and Nb/sub 3/Ge measured by tunneling
Tunnel junctions with good quasiparticle (Giaever) and pair (Josephson) tunneling characteristics have been made on electron-beam coevaporated thin films of some important high-temperature superconductors which have the A-15 crystalline structure. Using the thermally grown oxide of niobium tin to make Nb-Sn--oxide--Pb junctions we estimate the gap, ..delta../sub NbhyphenSn/, as a function of composition from the current-voltage characteristics. Stoichiometric Nb/sub 3/Sn is strong coupling with 2..delta../k/sub B/T/sub c/=4.2--4.4, whereas with less tin, Nb-Sn has a low T/sub c/ and becomes weak coupling. On vanadium silicon we could only make good junctions by evaporating a thin silicon layer, with thickness in the range 1.6--16 nm, on the fresh A-15 film before junction fabrication. V-Si is essentially weak coupling for all compositions with 2..delta../k/sub B/T/sub c/=3.5 +- 0.2. The characteristics of tunnel junctions on high-T/sub c/ niobium-germanium films always show evidence for multiple gaps and the data on this interesting material are more difficult to interpret.
- Research Organization:
- Department of Applied Physics, Stanford University, Stanford, California 94305
- OSTI ID:
- 5763808
- Journal Information:
- Phys. Rev., B: Condens. Matter; (United States), Vol. 20:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
GERMANIUM ALLOYS
ENERGY GAP
SUPERCONDUCTIVITY
TUNNEL EFFECT
NIOBIUM ALLOYS
TIN ALLOYS
VANADIUM SILICIDES
ELECTRIC CONDUCTIVITY
FILMS
JOSEPHSON EFFECT
QUANTITY RATIO
SUPERCONDUCTING JUNCTIONS
ALLOYS
ELECTRICAL PROPERTIES
PHYSICAL PROPERTIES
SILICIDES
SILICON COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
360104* - Metals & Alloys- Physical Properties
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Electronic
Magnetic
Optical
& Thermal Phenomena- (-1987)