Stress and surface morphology of TiNiCu thin films: effect of annealing temperature

Fu, Yong Qing, Du, Hejun, Zhang, Sam and Gu, Yan-Wei (2005) Stress and surface morphology of TiNiCu thin films: effect of annealing temperature. Surface and Coatings Technology, 198 (1-3). pp. 389-394. ISSN 0257-8972

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Abstract

TiNi-based films sputtered at room temperature are amorphous; thus, postsputtering annealing is a must because shape memory effect only occurs in their crystalline form. It is suggested that the lowest possible annealing temperature be used in a bid to conserve thermal processing budgets, and to minimize thermal stresses and possible interfacial reactions between film and its substrate. In this paper, Ti49.5Ni47.5Cu3 (at.%) films with a thickness of 3.5 μm were deposited on Si substrate by cosputtering of TiNi and Cu targets at room temperature, then annealed at different temperatures from 430 to 650 °C. Phase transformation behaviors, crystalline structure, residual stress and stress evolution of the films were systematically studied. At the gas pressure of 0.8 mTorr, the residual stress in the as-deposited films was 260 MPa, compressive. A minimum annealing temperature (450 °C) was necessary for film crystallization; thus, large thermal stress could be released significantly due to martensitic transformation. With increase of annealing temperature, crystallite and martensite plate sizes in the film increased; thus, both recovery stress and stress-increase rate increased, while the transformation temperatures shifted to higher values. The surface roughness increased drastically with increase of annealing temperature in correlation to martensitic transformation.

Item Type:	Article
Uncontrolled Keywords:	Annealing temperature; TiNiCu thin films; Surface morphology
Subjects:	F200 Materials Science
Department:	Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User:	Becky Skoyles
Date Deposited:	26 Mar 2015 16:50
Last Modified:	12 Oct 2019 19:06
URI:	http://nrl.northumbria.ac.uk/id/eprint/21857

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