Superconductor technology: apparatus – material – process – High temperature – per se – Having tc greater than or equal to 150 k
Patent
1992-04-21
1994-01-25
King, Roy
Superconductor technology: apparatus, material, process
High temperature , per se
Having tc greater than or equal to 150 k
505732, 505730, 427 62, 427596, 427557, 427314, 4271263, B05D 306, B05D 512
Patent
active
052815757
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a thin-film technology for an oxide superconductor, and more particularly to a manufacturing method for a high-temperature superconductive oxide thin film wherein a laser beam is irradiated onto a target to heat and evaporate oxide particles on the target and form the oxide thin film on a substrate.
BACKGROUND ART
FIG. 2 is a schematic diagram illustrating a manufacturing method for a high-temperature superconductive oxide thin film by means of laser. In this method, a laser beam 1 oscillated from a laser device (not shown) such as a YAG laser device or an ArF excimer laser device is obliquely irradiated onto a target 2 provided with an oxide for formation of a thin film to cut the bond of particles constituting the target and simultaneously excite the particles to a high energy state. Then, a luminous region called a plume consisting of active evaporated particles is formed, and when the plume reaches a substrate 3 heated by a heater 4 or the like, a high-temperature superconductive thin film is obtained.
In general, it is considered to be desirable that an oxygen partial pressure during film formation is made high from the viewpoint of improvement in Tc end of a superconductive oxide thin film. However, when the oxygen partial pressure during film formation is high, the plume is reduced in shape, resulting in a low probability of reaching of the active particles to the substrate. To cope with this, it is considered that a distance between the target and the substrate is reduced to allow the plume to easily reach the substrate. However, this method cannot be adopted because it is necessary to define a given distance between the target and the substrate so as to irradiate the laser beam onto the target.
Accordingly, as an adoptable method, the oxygen partial pressure is reduced during film formation, and after forming the thin film, a post-treatment is carried out such as by cooling and maintaining the thin film in the atmosphere of oxygen to incorporate oxygen particles into the thin film, thereby improving Tc end.
In this method, however, when a crystal structure is modified from a tetragonal system to an orthorhombic system by the incorporation of the oxygen particles into the thin film, a twin plane is formed to relax a strain of a lattice constant. It is known that the twin plane generates a magnetic flux trap to cause a noise in case of practically applying the superconductive thin film to a superconductive device.
DISCLOSURE OF INVENTION
The present invention has been accomplished in view of the above circumstances, and it provides a manufacturing method for a high-temperature superconductive oxide thin film wherein the superconductive oxide thin film is formed under a high oxygen partial pressure to obtain a high Tc end without a post-treatment of cooling and maintaining the thin film in the atmosphere of oxygen, and no noise is generated in the case that the superconductive oxide thin film is practically applied to a superconductive device.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic diagram illustrating a film forming method according to a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating a film forming method in the prior art;
FIGS. 3 and 4 are graphs illustrating the results of X-ray diffraction according to the preferred embodiment in comparison with the prior art;
FIG. 5 is a graph illustrating the result of electron beam diffraction of a substrate before and after laser irradiation;
FIGS. 6 and 7 are schematic diagrams illustrating film forming methods according to other preferred embodiments of the present invention; and
FIG. 8 is a graph illustrating a characteristic of a multi-layer film mirror employable in the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a typical example of a device to be preferably used in performing the manufacturing method according to the present invention. A target 2 having a predetermined oxide composition is retained by a targ
REFERENCES:
patent: 4743463 (1988-05-01), Ronn et al.
patent: 4970196 (1990-11-01), Kim et al.
patent: 4987006 (1991-01-01), Williams et al.
Koren et al, "Highly oriented as deposited superconducting laser ablated thin films of YiBa.sub.2 Cu.sub.3 O.sub.7-8 on SrTiO.sub.3, zirconia, and S.sub.i substrates", Appl. Phys. Lett. 53(23) Dec. 1988, pp. 2330-2332.
Journal of Applied Physics, vol. 66, No. 1, Jul. 1, 1989, pp. 457-459, E. Fogarassy, et al., "Laser-Induced Forward Transfer of High-Tc YBaCuO and BiSrCaCuO Superconducting Thin Films".
Hase Takashi
Izumi Hirohiko
Morishita Tadataka
Ohata Katsumi
Hitachi Densen Kabushiki Kaisha
International Superconductivity Technology Center
Kabushiki Kaisha Kobe Seiko Sho
King Roy
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