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Measurements of stiff-material compliance on the nanoscale using ultrasonic force microscopy

Dinelli, F and Biswas, SK and Briggs, GAD and Kolosov, OV (2000) Measurements of stiff-material compliance on the nanoscale using ultrasonic force microscopy. In: Physical Review B, 61 (20). pp. 13995-14006.

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Ultrasonic force microscopy (UFM) was introduced to probe nanoscale mechanical properties of stiff materials. This was achieved by vibrating the sample far above the first resonance of the probing atomic force microscope cantilever where the cantilever becomes dynamically rigid. By operating UFM at different set force values, it is possible to directly measure the absolute values of the tip-surface contact stiffness. From this an evaluation of surface elastic properties can be carried out assuming a suitable solid-solid contact model. In this paper we present curves of stiffness as a function of the normal load in the range of 0–300 nN. The dependence of stiffness on the relative humidity has also been investigated. Materials with different elastic constants (such as sapphire lithium fluoride, and silicon) have been successfully differentiated. Continuum mechanics models cannot however explain the dependence of stiffness on the normal force and on the relative humidity. In this high-frequency regime, it is likely that viscous forces might play an important role modifying the tip-surface interaction. Plastic deformation might also occur due to the high strain rates applied when ultrasonically vibrating the sample. Another possible cause of these discrepancies might be the presence of water in between the two bodies in contact organizing in a solidlike way and partially sustaining the load.

Item Type: Journal Article
Publication: Physical Review B
Publisher: American Physical Society
Additional Information: Copyright of this article belongs to American Physical Society.
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Date Deposited: 25 Jul 2008
Last Modified: 19 Sep 2010 04:48
URI: http://eprints.iisc.ac.in/id/eprint/15254

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