Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation
The discovery of a new class of copper oxide superconductors has led to the development of three major systems that exhibit superconducting properties. The Bi-Sr-Ca-Cu-O superconductors offer intrinsic advantages due to the high [Tc], chemical inertness and tolerance for a range of compositions. However, thin film research on these materials has progressed more slowly than the other cuprate systems. This dissertation examines the film growth, by laser ablation, of the Bi-Sr-Ca-Cu-O superconductors and the effect of the deposition parameters such as the laser target interaction, substrate temperature, target to substrate distance, deposition and cooling pressure, target type and processing and the substrate type. CO[sub 2] laser ablation was shown to give rise to a non-stoichiometric material transfer due to the low fluences and long pulse lengths. In situ superconducting thin films with T[sub c(0)]'s of 76 K could be deposited using the KrF laser at substrate temperatures of 5[degrees]C to 20[degrees]C below phases. Lower temperatures gave rise to a mixture of 2201 and glassy phases. An increase in the target to substrate distance led to a deterioration of the electrical and structural properties of the films due to a decrease in the energy for film formation. A maximum in T[sub c(0)] was observed at 450 mtorr as the deposition pressure was varied between 200 to 700 mtorr. Optimum oxygen incorporation could be achieved by cooling the films in high oxygen pressures and the best films were obtained with 700 torr cooling pressure. The oxygen deficiency of the hot pressed targets led to inferior properties compared to the conventionally sintered targets. The microwave surface resistance of the films measured at 35 GHz showed an onset at 80 K and dropped below that of copper at 30 K. The study of the laser ablation process in this system revealed the presence of a stoichiometric forward directed component and a diffuse evaporation component.
- Research Organization:
- Rutgers-the State Univ., New Brunswick, NJ (United States)
- OSTI ID:
- 7181844
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BISMUTH OXIDES
ABLATION
CALCIUM OXIDES
CUPRATES
STRONTIUM OXIDES
SUPERCONDUCTING FILMS
CARBON DIOXIDE LASERS
HIGH-TC SUPERCONDUCTORS
INTERMETALLIC COMPOUNDS
LASER RADIATION
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
BISMUTH COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
ELECTROMAGNETIC RADIATION
FILMS
GAS LASERS
LASERS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
STRONTIUM COMPOUNDS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
360207* - Ceramics
Cermets
& Refractories- Superconducting Properties- (1992-)
360201 - Ceramics
Cermets
& Refractories- Preparation & Fabrication