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Title:Physical properties of thin film, metastable titanium(0.5)aluminum(0.5)nitrogen alloys deposited by reactive magnetron sputtering
Author(s):McIntyre, Dale Charles
Doctoral Committee Chair(s):Greene, Joseph E.
Department / Program:Engineering, Metallurgy
Engineering, Materials Science
Discipline:Engineering, Metallurgy
Engineering, Materials Science
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Metallurgy
Engineering, Materials Science
Abstract:Metastable, NaCl-structure, polycrystalline Ti$\sb{0.5}$Al$\sb{0.5}$N films, 3-5 $\mu$m thick, have been deposited on stainless-steel substrates by d.c. reactive magnetron sputtering. The effects of low-energy (E $\leq$ 250 eV) ion bombardment during deposition on thin film microstructure, oxidation properties, and optical reflectance of the metastable alloy were evaluated.
The ion flux to deposition flux ratio was about unity and for an applied substrate bias V$\sb{\rm s}$, the average energy of the ions impinging on the growing film was $\simeq$ eV$\sb{\rm s}$, for V$\sb{\rm s}$ $\geq$ 50 V. Films deposited with V$\sb{\rm s}$ = 0 had a columnar microstructure, low dislocation density, and were voided and porous. The primary effect of ion-irradiation at low acceleration energies (V$\sb{\rm s}$ $\leq$ 120 V) was film densification by the elimination of voids and pores, while at higher energies (V$\sb{\rm s}$ $>$ 120 V) the primary effect of ion-bombardment was an increase in dislocation density.
Films deposited with V$\sb{\rm s}$ of O and 150 V were oxidized in O$\sb2$ at temperatures between 750$\sp\circ$C and 900$\sp\circ$C. Oxidation involved both the initial formation of an oxide overlayer and the subsequent growth of oxide crystallites. The diffusion limited growth of the oxide overlayer involved the transport of Al and O through a Al-rich oxide/Ti-rich oxide bilayer and followed the same kinetics for both 0 and 150 V films. The oxide crystallites, primarily composed of Ti and O, were first observed at tensile cracks in the V$\sb{\rm s}$ = 0 films when oxide overlayer thicknesses, d$\sb{\rm ox}$, were approximately 150 nm, and were also later observed at intragranular defects when d$\sb{\rm ox}$ $\simeq$ 400 nm. The initial appearance of crystallites was observed at larger d$\sb{\rm ox}$ for the V$\sb{\rm s}$ = 150 V samples.
The optical reflectance, R, of the metastable films was measured in the visible and infrared spectral regions at wavelengths, $\lambda$, in the range 250 nm $\leq$ $\lambda$ $\leq$ 2400 nm. The near-infrared R the films showed the most dependence on V$\sb{\rm s}$, because of the variation in conduction-electron mobility with film defect density. Valance-band spectra from Ti$\sb{0.5}$Al$\sb{0.5}$N, collected using X-ray photoemission spectroscopy, showed that metastable Ti$\sb{0.5}$Al$\sb{0.5}$N had $\simeq$ 40% fewer conduction electrons than NaCl structure TiN.
Issue Date:1989
Rights Information:Copyright 1989 McIntyre, Dale Charles
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9010953
OCLC Identifier:(UMI)AAI9010953

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