High-temperature superconducting thin films and their application to superconducting-normal-superconducting devices
The existence of the proximity effect between the high temperature superconductor YBa[sub 2]Cu[sub 3]O[sub 7] (YBCO) and normal metal thin films has been demonstrated, and this effect has been exploited to produce lithographically fabricated superconducting-normal-superconducting (SNS) Josephson junctions. Improvement of the fabrication processes has led to new methods of in-situ film growth and plasma etching of YBCO, as well a YBCO-compatible processes for the deep-ultraviolet and electron-beam lithography required to fabricate submicron device structures. This proximity effect approach helps to circumvent the short coherence length ([xi] [approximately] 3 nm) characteristic of the high T[sub c] superconductors. In a clean normal metal such as gold or silver the relevant coherence length is governed by the higher Fermi velocity and longer mean free path. A Josephson device containing a normal metal weak link can be longer than an ideal all-YBCO microbridge (dimensions comparable to [xi]). Initially, SNS devices were fabricated and showed evidence for a supercurrent through the normal region. Properly spaced Shapiro steps as a function of microwave frequency were observed. This result was evidence for a proximity effect between a normal metal and YBCO. The fabrication process was not sufficiently reproducible, so new techniques were developed. In-situ film growth and fabrication is desirable to minimize contamination of and damage to the surface of the superconductor. In-situ reactive coevaporation of YBCO was demonstrated. Patterning of these in-situ films in to a structure required the development of a low-damage reactive ion etch. New lithographic techniques were developed to minimize chemical degradation of the superconductor. Deposition of gold onto heated device structures was demonstrated to produce a superior SNS device. The application of YBCO thin films to passive microwave devices and to active superconducting circuits was evaluated.
- Research Organization:
- Boston Univ., MA (United States)
- OSTI ID:
- 7071574
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
Similar Records
Combined method of electron-beam lithography and ion implantation techniques for the fabrication of high-temperature superconductor Josephson junctions
Progress in high-temperature superconducting transistors and other devices; Proceedings of the SPIE Meeting, Vol. 1394, Santa Clara, CA, Oct. 4, 5, 1990
Related Subjects
JOSEPHSON JUNCTIONS
ETCHING
FABRICATION
SUPERCONDUCTING FILMS
PROXIMITY EFFECT
BARIUM OXIDES
CUPRATES
HIGH-TC SUPERCONDUCTORS
INTERMETALLIC COMPOUNDS
YTTRIUM OXIDES
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
BARIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
FILMS
JUNCTIONS
OXIDES
OXYGEN COMPOUNDS
SUPERCONDUCTING JUNCTIONS
SUPERCONDUCTORS
SURFACE FINISHING
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360207* - Ceramics
Cermets
& Refractories- Superconducting Properties- (1992-)
360201 - Ceramics
Cermets
& Refractories- Preparation & Fabrication