MICROSTRUCTURAL VARIATIONS IN ALUMINUM-OXIDE COATINGS DEPOSITED USING A DUAL BEAM ION SYSTEM

We have sputter-deposited aluminum oxide coatings using a dual ion beam system with a mixture of argon plus 10% oxygen as the working gas. Ambient substrate temperatures and substrate temperatures of 360°C were maintained. The coatings were deposited at deposition rates between 7 and 10 nm/min, with and without concurrent ion bombardment from the second ion gun. Substantial variations in the microstructure and the amount of entrained gas in the coatings were observed. The coatings contain a mixture of varying amounts of γ-Al2O3and amorphous aluminum oxide. Relatively large, 0.5 μm islands of γ-Al2O3 crystallites surrounded by an amorphous matrix were observed in coatings deposited onto heated substrates with ion bombardment from the second ion gun during deposition. Coatings bombarded with a second ion beam during deposition contain more argon as determined by energy dispersive x-ray analysis. The Raman spectra exhibited by the coatings suggest a variation in chemical reactivity and/or porosity which depends on the deposition conditions. © 1990, American Vacuum Society. All rights reserved.