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Stress induced phase transition in monomolecular perfluroalkylsilane film self assembled on aluminium surface

Biswas, SK and Devaprakasam, D (2006) Stress induced phase transition in monomolecular perfluroalkylsilane film self assembled on aluminium surface. In: Symposium on Surface Engineering for Manufacturing Applications held at the 2005 MRS Fall Meeting, Nov 28-Dec 01, 2005, Boston, MA,, pp. 241-246.

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We control the stiffnesses of two dual double cantelevers placed in series to control penetration into a perflurooctyltrichlorosilane monolayer self assembled on aluminium and silicon substrates. The top cantilever which carries the probe is displaced with respect to the bottom cantilever which carries the substrate, the difference in displacement recorded using capacitors gives penetration. We further modulate the input displacement sinusoidally to deconvolute the viscoelastic properties of the monolayer. When the intervention is limited to the terminal end of the molecule there is a strong viscous response in consonance with the ability of the molecule to dissipate energy by the generation of gauche defects freely. When the intervention reaches the backbone, at a contact mean pressure of 0.2GPa the damping disappears abruptly and the molecule registers a steep rise in elastic modulus and relaxation time constant, with increasing contact pressure. We offer a physical explanation of the process and describe this change as due to a phase transition from a liquid like to a solid like state.

Item Type: Conference Paper
Publisher: Materials Research Society
Additional Information: Copyright of this article belongs to Materials Research Society.
Department/Centre: Division of Mechanical Sciences > Mechanical Engineering
Date Deposited: 26 Aug 2010 06:15
Last Modified: 26 Aug 2010 06:15
URI: http://eprints.iisc.ac.in/id/eprint/30675

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