Title :
Effect of Au contact layer on the microwave performance of YBa2Cu3O7-x thin films
Author :
Zaitsev, A.G. ; Schneider, R. ; Aidam, R. ; Linker, G. ; Ratzel, F. ; Reiner, J. ; Smithey, R. ; Geerk, J.
Author_Institution :
Inst. fur Festkorperphys., Forschungszentrum Karlsruhe, Germany
fDate :
3/1/2001 12:00:00 AM
Abstract :
The microwave surface resistance (Rs) of YBCO films sputtered simultaneously on both sides of CeO2 coated sapphire wafers of 3 inch diameter was measured using the disk resonator technique at a frequency of 1.92 GHz. Gold layers were deposited on the unpatterned side of the resonator, and the microwave losses were measured in the Au-contacted YBCO films. Although the Au layer was not directly exposed to the microwave power, it dramatically increased the effective Rs of the YBCO film, while leaving the effective surface reactance (Xs) almost unchanged. The Rs-enhancement was examined experimentally and theoretically in terms of the impedance transformation approach as a function of the Au and YBCO film properties. Furthermore, the technique appeared suitable for the determination of the absolute value of the London penetration depths (λL) in the double-sided YBCO films. The resulting temperature dependencies of λL were in a good agreement with those estimated by the conventional frequency-shift technique
Keywords :
barium compounds; dielectric losses; electric reactance; gold; high-frequency effects; high-temperature superconductors; penetration depth (superconductivity); superconducting thin films; surface conductivity; yttrium compounds; 1.92 GHz; Al2O3; Au contact layer; Au-YBa2Cu3O7; CeO2; CeO2 coated sapphire wafers; London penetration depth; disk resonator technique; effective surface reactance; impedance transformation; microwave losses; microwave surface resistance; temperature dependence; thin films; Electrical resistance measurement; Frequency estimation; Frequency measurement; Gold; Loss measurement; Microwave measurements; Microwave theory and techniques; Surface impedance; Surface resistance; Yttrium barium copper oxide;
Journal_Title :
Applied Superconductivity, IEEE Transactions on