Process for preparing high crystallinity oxide thin film

A process for preparing an oxide thin film which has a crystalline, clean and smooth surface on a substrate. The process is conducted by using an apparatus comprising a vacuum chamber in which an oxidizing gas of O.sub.2 including O.sub.3 can be supplied near the substrate so that pressure around the substrate can be increased while maintaining high vacuum near an evaporation source and Knudsen cell evaporation sources arranged in the vacuum chamber wherein the substrate is heated, molecular beam of constituent atoms of the oxide excluding oxygen are supplied from the K cell evaporation sources, an oxidizing gas is locally supplied to the vicinity of the substrate and a growing thin film is illuminated by ultraviolet.

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What is claimed is:

1. A process for preparing a film formed of an oxide material on a substrate by using an apparatus comprising a vacuum chamber in which an oxidizing gas of O.sub.2 includingO.sub.3 is supplied near the substrate so that pressure around the substrate is increased to 5.times.10.sup.-7 to 5.times.10.sup.-6 Torr while maintaining a high vacuum of 1.times.10.sup.-11 to 1.times.10.sup.-9 Torr around an evaporation source andKnudsen cell evaporation sources arranged in the vacuum chamber wherein the substrate is heated, molecular beam of constituent atoms of the oxide excluding oxygen are supplied from the K cell evaporation sources, an oxidizing gas of O.sub.2 includingabout 70 volume percent O.sub.3 is locally supplied to the vicinity of the substrate and a growing thin film is illuminated by ultraviolet having a wavelength of 150 to 172 nanometers so as to increase the O.sub.3 content of the oxidizing gas.

2. A process as claimed in claim 1, wherein the ultraviolet is produced by a low pressure mercury lamp.

3. A process as claimed in claim 2, wherein the low pressure mercury lamp is disposed at a distance of 100 to 500 millimeters from the substrate.

4. A process as claimed in claim 2, wherein the low pressure mercury lamp has an output of 5 to 100 watt.

5. A process claimed in claim 1, wherein the process is conducted while the oxidizing gas is supplied onto a deposition plane of the substrate.

6. A process as claimed in claim 1, wherein the film is a c-axis orientated Y.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x oxide superconductor thin film.

7. A process as claimed in claim 6, wherein the process is conducted at a substrate temperature of 630 to 670.degree. C.

8. A process as claimed in claim 7, wherein the process is conducted at a substrate temperature of 650.degree. C.