Epitaxial thin films

Abstract

Epitaxial thin films for use as buffer layers for high temperature superconductors, electrolytes in solid oxide fuel cells (SOFC), gas separation membranes or dielectric material in electronic devices, are disclosed. By using CCVD, CACVD or any other suitable deposition process, epitaxial films having pore-free, ideal grain boundaries, and dense structure can be formed. Several different types of materials are disclosed for use as buffer layers in high temperature superconductors. In addition, the use of epitaxial thin films for electrolytes and electrode formation in SOFCs results in densification for pore-free and ideal grain boundary / interface microstructure, Gas separation membranes for the production of oxygen and hydrogen are also disclosed. These semipermeable membranes are formed of high-quality, dense, gas-tight, pinhole free sub-micron scale layers of mixed-conducting oxides on porous ceramic substrates. Epitaxial thin films as dielectric material in capacitors are also taught herein. Capacitors are utilized according to their capacitance values which are dependent on their physical structure and dielectric permittivity. The epitaxial thin films of the current invention form low-loss dielectric layers with extremely high permittivity. This high permittivity allows for the formation of capacitors that can have their capacitance adjusted by applying a DC bias between their electrodes.

Description

RELATED CASES [0001] This application is a divisional of U.S. Utility patent application Ser. No. 09 / 889,237, filed Jul. 10, 2001, which is a U.S. National filing of International application No. PCT / US00 / 00824, filed Jan. 12, 2000 and claiming priority to U.S. Provisional Patent Application Ser. No. 60 / 115,519, filed Jan. 12, 1999.GOVERNMENT CONTRACT [0002] The United States Government has rights in this invention pursuant to Contract No. F33615-98-C5418 awarded by the United States Department of Defense, and Contract Nos. DE-FG02-97ER82345, ACQ-9-29612-01 and 4500011833 awarded by the United States Department of Energy.FIELD OF THE INVENTION [0003] The invention relates to epitaxial thin films, and more particularly to epitaxial thin films for use as, inter alia, buffer layers for high temperature superconductors, electrolytes in solid oxide fuel cells (SOFC), gas separation membranes or dielectric material in electronic devices. BACKGROUND OF THE INVENTION [0004] While the abilit...

AI Technical Summary

Benefits of technology

[0014] In the field of high-temperature superconductors, second generation superconducting wire is typically made up of four components, a flexible metal substrate, a buffer layer, a superconducting layer such as YBa2Cu3O7-x(YBCO), and a final layer in the form of an insulating or conducting layer. Buffer layers are employed to protect the metal substrate from oxidizing during the superconductor application as well as to prevent diffusion of the metal substrate into the superconducting layer. Buffer layers must also impart the desired crystallographic texture to the superconducting layer. High temperature superconductors (HTSC) have enormous potential for electric power applications such as current leads, motors, transmission cables, generators, transformers and current limiters, however, the cost of HTSC wire must be reduced to levels comparable to copper to enable most practical applications. Even the most promising forecasts for mass production cost of state-of-the-art HTSC powder-in-tube wire are well in excess of this target; this wire also suffers from performance limitations. Therefore, processes amenable to scale-up that will facilitate YBCO and associated buffer layer deposition at a low cost with good control of stoichiometry are required for high volume, low cost manufacturing of HTSC wires. The atmospheric pressure combustion chemical vapor deposition (CCVD) process and the controlled atmosphere chemical vapor deposition (CACVD) technique use inexpensive chemical precursors and low cost equipment, and can be configured for continuous, uninterrupted processing of wires and tapes. Prior methods and products cannot compare to the reduced expense and the flexibility of the CCVD methods and high quality epitaxial buffer layers produced thereby.

[0031] It is still another object of the invention to provide electrically adjustable capacitors by using dielectric layers with high permittivity and low loss.

Problems solved by technology

Even the most promising forecasts for mass production cost of state-of-the-art HTSC powder-in-tube wire are well in excess of this target; this wire also suffers from performance limitations.

Prior methods and products cannot compare to the reduced expense and the flexibility of the CCVD methods and high quality epitaxial buffer layers produced thereby.

However, “weak link” or dissipative behavior at grain boundaries within the current path for YBCO has been this material's major limitation.

However, all of these methods have expense and scalability limitations.

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