Process for preparing high crystallinity oxide thin film

DETAILED DESCRIPTION Accordingly, it is an object of the present invention to provide a process for preparing an oxide thin film having clean and smooth surfaces with high crystallinity and excellent properties, which has overcome the above mentioned defects of the conventional ones.
Another object of the present invention is to provide a process for preparing an oxide thin film on an oxide superconductor thin film without inter diffusion, which has overcome the above mentioned defects of the conventional ones.
The above and other objects of the present invention are achieved in accordance with the present invention by 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 including O.
sub.
3 can be supplied near the substrate so that pressure around the substrate can be increased while maintaining high vacuum around an evaporation source and evaporation sources of Knudsen cell (K cell) 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 cells and an oxidizing gas is locally supplied to the vicinity of the substrate.
In accordance with the present invention, the pressure of the oxidizing gas at the vicinity of the substrate was evacuated between 1.
times.
10.
sup.
-6 and 5.
times.
10.
sup.
-5 Tort at a background pressure of 1.
times.
10.
sup.
-11 to 1.
times.
10.
sup.
-9 Torr.
This quite low background pressure described above means that there is no leak nor any gas generation at the vacuum chamber of the apparatus.
Therefore, no contaminant, for example hydrocarbonates or metal carbides, is deposited on or within the oxide thin film prepared by the process in accordance with the present invention.
In a preferred embodiment, the oxidizing gas is O.
sub.
2 including more than 5 volume percent O.
sub.
3 which has higher oxidation ability than pure O.
sub.
2 appropriate to oxide thin film deposition.
In one preferred embodiment, the deposition process is conducted while the oxidizing gas is injected onto a specimen surface