The preparation of thin films of some oxides by the pyrolysis method

Abstract

It is shown that the pyrolysis method is quite an attractive technique for the preparation of oxide films of many metals with predetermined properties in a wide range of compositions. The use of oxygen in the pyrolysis process has made it possible to obtain filmsmore perfect in structure (oriented and single-crystal). Some experimental data on the preparation of semi-conductor and dielectric oxide films (ZnO, In 2O 3, Al 2O 3) by pyrolysis of corresponding metal-containing organic compounds (Zn propionate, In acetylacetonate, Al ethylate) are described. A relationship was established between the structure of the films and the conditions of their formation. In the process it was revealed that the nature of the substrate and its temperature were the determining factors. Electron diffraction analysis showed that the structure of the In 2O 3 films changed from an amorphous to a well oriented one and this corresponded with a change of resistivity from 10 12 to 10 2 ohm cm. It was possible to obtain ZnO single-crystal films on mica with a resistivity of 10 8 ohm cm. Films with different resistivities (10 7–10 12 ohm cm) were obtained by the decomposition of previously co-deposited aluminium and chromium acetylacetonates. The difference in resistivity was shown to depend on the Cr 2O 3 content of the deposited films. The high dielectric strength of Al 2O 3 polycrystalline films (thickness 3–5μ) made it possible to use them as insulating coatings for radio valve heaters.