Microscopic characterization of stress in thin silicon films is essential for successful design of the devices such as solar cells, thin-film transistor arrays for liquid-crystal displays, micro-electro-mechanical systems (MEMS) etc.
We have used Plasma Enhanced Chemical Vapor Deposition (PECVD) to deposit thin films (~1 µm) of nanocrystalline silicon on platinum coated AFM cantilevers. Microscopic measurements of Raman scattering were used to study either internal stress or additional stress induced in the films by bending the cantilevers using a nanomanipulator (Kleindiek Nanotechnik MM3A).
The effect of mechanical stress on the silicon Raman spectrum has been extensively studied and documented, but the effect is usually very small (shift of the dominant TO-LO peak by ~ 0.1 cm-1) [1, 2]. With our technique one can obtain order of magnitude greater shifts because of the excellent elastic properties of the cantilever.
Our approach also allows investigating other mechanical properties of thin Si films, such as adhesion to flexible substrates and durability of the films.
[1] S. Kouteva-Arguirova, W. Seifert, M. Kittler, J. Reif, Materials Science and Engineering B102 (2003) 37-42
[2] Xiaoming Wu, Jianyuan Yu, Tianling Ren, Litian Liu, Microelectronic Journal 38 (2007) 87-90
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