The effective microwave surface impedance of high T sub c thin films

Journal Article · Fri Jun 01 04:00:00 EDT 1990 · Journal of Applied Physics; (USA)

DOI:https://doi.org/10.1063/1.345037· OSTI ID:6974346

Klein, N; Chaloupka, H; Mueller, G; Orbach, S; Piel, H ^[1]; Roas, B; Schultz, L ^[2]; Klein, U; Peiniger, M ^[3]

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1. Bergische Universitaet, Gesamthochschule Wuppertal, D-5600 Wuppertal 1, West Germany (DE)
2. Siemens AG, Research Laboratories, D-8520 Erlangen (West Germany)
3. Interatom GmbH, D-5060 Bergisch-Gladbach (West Germany)

The dependence of the effective surface impedance {ital Z}{sub eff}={ital R}{sub eff}+{ital iX}{sub eff} of superconducting thin films on the film thickness {ital d}, on the magnetic field penetration depth {lambda}, and on the dielectric properties of the substrate material is investigated theoretically by means of impedance transformations. It was found that the effective surface resistance {ital R}{sub eff} can be expressed by {ital R}{sub {ital Sf}}({ital d}/{lambda})+{ital R}{sub trans} where {ital R}{sub {ital S}} is the intrinsic surface resistance of the superconductor. The function {ital f}({ital d}/{lambda}) describes the altered current density distribution in the film. {ital R}{sub trans} arises from power transmission through the film. It depends on {ital d} and {lambda} as well as on the dielectric properties of the substrate material and is significantly altered in the case of a resonant background. The effective surface reactance {ital X}{sub eff} of a superconducting thin film can be expressed by {ital X}{sub {ital S}} cosh({ital d}/{lambda}) where {ital X}{sub {ital S}}={omega}{mu}{sub 0}{lambda} is the intrinsic surface reactance. Measurements of {ital Z}{sub eff} at 87 GHz have been performed for YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thin films grown epitaxially by laser ablation on SrTiO{sub 3}, MgO, and LaAlO{sub 3}. With the best films, {ital R}{sub eff} (77 K) values of 21 m{Omega} and {ital R}{sub {ital S}} (77 K) values of 8 m{Omega} were achieved. The temperature dependence of {lambda} was found to be in good agreement to both weak-coupling BCS theory in the clean limit and the empirical two-fluid model relation with {lambda} (0 K) values ranging from 140 to 170 nm and 205 to 250 nm, respectively.

• OSTI ID: 6974346
• Journal Information: Journal of Applied Physics; (USA), Journal Name: Journal of Applied Physics; (USA) Vol. 67:11; ISSN 0021-8979; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ABLATION
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
BCS THEORY
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
DIELECTRIC PROPERTIES
DIMENSIONS
ELECTRIC IMPEDANCE
ELECTRICAL PROPERTIES
ELECTROMAGNETIC RADIATION
EPITAXY
FILMS
FREQUENCY RANGE
GHZ RANGE
GHZ RANGE 01-100
IMPEDANCE
LASER RADIATION
MICROWAVE RADIATION
OXIDES
OXYGEN COMPOUNDS
PENETRATION DEPTH
PHYSICAL PROPERTIES
RADIATIONS
SUBSTRATES
SUPERCONDUCTING FILMS
THICKNESS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES