Reversible surface morphology in shape-memory alloy thin films

Reversible surface morphology can be used for significantly changing many surface properties such as roughness, friction, reflection, surface tension, etc. However, it is not easy to realize atop metals at micron scale around ambient temperature. In this paper, we demonstrate that TiNi and TiNi base...

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Bibliographic Details
Published in:Journal of applied physics 2009-02, Vol.105 (3), p.033517-033517-5
Main Authors: Wu, M. J., Huang, W. M., Fu, Y. Q., Chollet, F., Hu, Y. Y., Cai, M.
Format: Article
Language:English
Subjects:
Engineering Sciences
Materials and structures in mechanics
Mechanics
Micro and nanotechnologies
Microelectronics
Physics
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Summary:Reversible surface morphology can be used for significantly changing many surface properties such as roughness, friction, reflection, surface tension, etc. However, it is not easy to realize atop metals at micron scale around ambient temperature. In this paper, we demonstrate that TiNi and TiNi based (e.g., TiNiCu) shape-memory thin films, which are sputter-deposited atop a silicon wafer, may have different types of thermally-induced reversible surface morphologies. Apart from the well-known surface relief phenomenon, irregular surface trenches may appear in the fully crystallized thin films, but disappear upon heating. On the other hand, in partially crystallized thin films, the crystalline structures (islands) appear in chrysanthemum-shape at high temperature; while at room temperature, the surface morphology within the islands changes to standard martensite striations. Both phenomena are fully repeatable upon thermal cycling. The mechanisms behind these phenomena are investigated.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.3075773