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Effect of Concurrent Ion Bombardment on Structure and Composition of Ion Sputter-Deposited Ni-Ti Thin Films

Published online by Cambridge University Press:  25 February 2011

D. S. Grummon
Affiliation:
Department of Materials Science and MechanicsMichigan State University, E. Lansing, MI 48824
L. Chang
Affiliation:
Department of Materials Science and MechanicsMichigan State University, E. Lansing, MI 48824
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Abstract

Thin films of approximately equiatomic NiTi have been produced by ion beam sputtering, and by ion beam assisted deposition (IBAD), using 0.1 and 0.5 keV argon ions at fluences giving ion/atom arrival ratios (R-ratios) ranging between 0.26 and 2.21. Ion beam sputtering produced amorphous films which showed several percent titanium loss relative to the alloy target composition. Concurrent irradiation of the growing films with argon ions accentuated the titanium depletion, and R-ratios greater than approximately 1.4 at an assist-beam energy of 0.5keV produced resputtering rates that exceeded the deposition rate. Analysis of experiments with assist-beam energies of 0.5 keV produced a value of 1.75 for εTiNi, the ratio of sputteryields for titanium and nickel, in an amorphous alloy film at approximately 325K. Though data for 0.1 keV assist-beam irradiation could be interpreted to yield a similar value for εTiNi, resputtering at these energies displayed unexpected dependencies on R-ratio, and is apparently sensitive to the assist-beam incidence angle as well as the R-ratio. No evidence of crystallization of the films was found for the R-ratios examined. However, concurrent ion irradiation produced phenomenological evidence of short range ordering. Nanophase precipitates observed in TEM foils from films produced by ion beam assisted deposition, discovered in previous work and there identified as Ni3Ti, have been found in fact to be titanium nitride.

Type
Research Article
Copyright
Copyright © Materials Research Society 1992

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References

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