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ENHANCED Tc OF FILMS OF La-Ba-Cu-O TYPE COMPOUNDS

IP.com Disclosure Number: IPCOM000035097D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gallagher, WJ: AUTHOR [+2]

Abstract

The largest observed increase in Tc with hydrostatic pressure for narrow band transition metals superconductors is 11.3K for lanthanum. The change is explained semi-quantitatively in terms of the electron- phonon interaction in narrow-band metals and depends on such factors as the compressibility and structural instabilities in the metal. The largest increase in Tc ( 13K) with hydrostatic pressure (10 kb or 1010 dynes/cm2) for a compound was reported for the superconductor, (La1-xBax)2CuO4-y . Presumably, even higher Tc values are obtained if strontium is substituted for barium.

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ENHANCED Tc OF FILMS OF La-Ba-Cu-O TYPE COMPOUNDS

The largest observed increase in Tc with hydrostatic pressure for narrow band transition metals superconductors is 11.3K for lanthanum. The change is explained semi-quantitatively in terms of the electron- phonon interaction in narrow-band metals and depends on such factors as the compressibility and structural instabilities in the metal. The largest increase in Tc ( 13K) with hydrostatic pressure (10 kb or 1010 dynes/cm2) for a compound was reported for the superconductor, (La1-xBax)2CuO4-y . Presumably, even higher Tc values are obtained if strontium is substituted for barium.

Compressive stress can be applied to thin films of these compounds by depositing an overlayer with high intrinsic compressive stress onto the film to maximize its Tc . High melting point transition metals and transition metal oxides deposited near room temperature by magnetron sputtering have compressive intrinsic stresses in the 1010 dynes/cm2 range. The stress is dependent upon the rate of deposition, the ion energy and the sputter gas pressure. Additional stress can be applied to the (La1-xBax)2CuO4-y superconductor by processing prestressed wafers (e.g., wafers with their curvature adjusted by applied forces) and then relieving the stress after processing such that additional compressive stress is applied to the (La1-xBax)2CuO4-y superconductor.

Extensions of the overlayer approach may be used if the stress in the overlayer films does...