FORMATION OF AL2O3 FILMS BY LOW-PRESSURE CVD USING ATI-O2 SYSTEM AND EVALUATION OF CORROSION RESISTANCES OF THE FILMS

In order to obtain high corrosion-resistant oxide films, Al2O3 films were formed on the Pt substrate by low pressure CVD technique using aluminum-tri-isopropoxide (ATI, Al(OC3H7)3) and oxygen. The changes in the composition, structure, and corrosion resistance of the films were investigated as functions of deposition and heat-treatment temperatures. The structure of the films was amorphous at deposition temperatures in the range of 473-773 K. The refractive index of the films increased with increasing deposition temperature, showing the increase in density of the films. The corrosion resistance of the films in 1.0 and 12.0 kmol.m-3 HCl and 0.01 kmol.m-3 NaOH solutions increased with increasing deposition temperature. Films deposited at 623 K were transformed into gamma-Al2O3 and alpha-Al2O3 by annealing at 1073 K and 1173 K, respectively. The crystallized films hardly dissolved in a 12.0 kmol.m-3 HCl solution.