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Microstructural variations in aluminum oxide coatings deposited using a dual beam ion system

Panitz, J.K.G.; Hills, C.R.; Tallant, D.R.

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{degree}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 {gamma}-Al{sub 2}O{sub 3} and amorphous aluminum oxide. Relatively large, 0.5 {mu}m islands of {gamma}-Al{sub 2}O{sub 3} 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. 18 refs., 6 figs.