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Compositional Effects on the Crystallization Kinetics of Nickel Titanium Thin Films

Published online by Cambridge University Press:  01 July 2005

Hai Ni ,
Hoo-Jeong Lee  and
Ainissa G. Ramirez
Hai Ni
Affiliation:
Department of Mechanical Engineering, Yale University, New Haven, Connecticut 06520
Hoo-Jeong Lee
Affiliation:
Department of Mechanical Engineering, Yale University, New Haven, Connecticut 06520
Ainissa G. Ramirez*
Affiliation:
Department of Mechanical Engineering, Yale University, New Haven, Connecticut 06520
*
a)Address all correspondence to this author. e-mail: ramirez@stanfordalumni.org
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Abstract

The crystallization and phase transformations of amorphous NiTi thin films were studied using in situ transmission electron microscopy (TEM). These films were sputter-deposited onto micromachined silicon-nitride membranes and subjected to heating and cooling conditions. The microstructural evolution was monitored and recorded. Kinetic parameters such as the nucleation rate, growth rate, and area-fraction transformed were independently determined by noting the number of grains per frame and their change in size. Using the Johnson–Mehl–Avrami–Kolmogorov analysis, fitted kinetic parameters were determined and found to be consistent with TEM observations. To explore the compositional sensitivity of crystallization, samples near-equiatomic and slightly Ti-rich were studied with these methods. TEM micrographs show that equiatomic films exhibit polymorphic crystallization while samples that are slightly off-stoichiometry showed more complicated behavior.

Keywords

Microelectrical mechanical (MEMS)Thin filmTransmission electron microscopy (TEM)
Type
Articles
Information
Journal of Materials Research , Volume 20 , Issue 7 , July 2005 , pp. 1728 - 1734
Copyright
Copyright © Materials Research Society 2005

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References

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