Oxidation of metastable single-phase polycrystalline Ti sub 0. 5 Al sub 0. 5 N films: Kinetics and mechanisms

Journal Article · Thu Feb 01 04:00:00 EST 1990 · Journal of Applied Physics; (USA)

DOI:https://doi.org/10.1063/1.345664· OSTI ID:7203268

McIntyre, D; Greene, J E ^[1]; Hakansson, G; Sundgren, J ^[2]; Muenz, W ^[3]

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1. Department of Materials Science, Coordinated Science Laboratory and the Materials Research Laboratory, University of Illinois, 1101 West Springfield Avenue, Urbana, Illinois 61801 (USA)
2. Thin Film Group, Department of Physics, Linkoeping University S-58183, Linkoeping, (Sweden)
3. Leybold AG, D-6450 Hanau, (Federal Republic of Germany)

Metastable single-phase, NaCl-structure, polycrystalline Ti{sub 0.5}Al{sub 0.5}N alloy films have been shown to exhibit much better high-temperature (750--900 {degree}C) oxidation resistance than polycrystalline TiN films grown under similar conditions. The Ti{sub 0.5}Al{sub 0.5}N alloys, {congruent}3 {mu}m thick, were deposited at temperatures between 400 and 500 {degree}C on stainless-steel substrates by dc magnetron sputter deposition in mixed Ar+N{sub 2} discharges with an applied negative substrate bias {ital V}{sub {ital s}} of either 0 or 150 V. Oxidation in pure O{sub 2} initially occurred at a rate that varied parabolically with time. The oxide overlayers consisted of two partially crystalline sublayers, the upper one Al-rich and the lower one Ti-rich, with no measurable N concentrations in either. Inert-marker transport experiments showed that oxidation proceeded by the simultaneous outward diffusion of Al to the oxide/vapor interface and inward diffusion of O to the oxide/nitride interface. The oxidation rate constant K increased with oxidation temperature {ital T}{sub ox} at a rate much higher than would be predicted from a simple exponential dependence due to changes in the oxide microstructure (increased crystallinity) with increasing {ital T}{sub ox}. At {ital T}{sub ox} {ge}850 {degree}C, O transport became the rate-limiting step. After oxidation times, ranging from 6 h at 750 {degree}C to 7 min at 900 {degree}C, oxide crystallites, exhibiting a tetragonal rutile TiO{sub 2} structure, were observed in {ital V}{sub {ital s}}=0 samples to grow at an accelerated rate up through cracks in the oxide overlayer. The formation of these crystallites was postponed until a much later stage in oxide-overlayer development for samples grown with {ital V}{sub {ital s}}=150 V.

• DOE Contract Number: AC02-76ER01198
• OSTI ID: 7203268
• Journal Information: Journal of Applied Physics; (USA), Journal Name: Journal of Applied Physics; (USA) Vol. 67:3; ISSN 0021-8979; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360205* -- Ceramics
Cermets
& Refractories-- Corrosion & Erosion
ALUMINIUM
ALUMINIUM COMPOUNDS
ALUMINIUM NITRIDES
CHEMICAL REACTIONS
CRYSTALS
DIFFUSION
ELEMENTS
FILMS
METALS
NITRIDES
NITROGEN COMPOUNDS
NONMETALS
OXIDATION
OXYGEN
PNICTIDES
POLYCRYSTALS
SPUTTERING
TITANIUM COMPOUNDS
TITANIUM NITRIDES
TRANSITION ELEMENT COMPOUNDS