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

Year: 2000

Authors: Dinelli F., Biswas S.K., Briggs G.A.D., Kolosov O.V.

Autors Affiliation: Department of Materials, University of Oxford, Parks Road, OX1 3PH Oxford, United Kingdom; Indian Institute of Science, Bangalore, India

Abstract: 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.

Journal/Review: PHYSICAL REVIEW B

Volume: 61 (20)      Pages from: 13995  to: 14006

More Information: ACKNOWLEDGMENTS: F.D. and O.V.K would like to thank the Paul Instrument Fund and EPSRC support (GR/L02234) for the development of UFM. F.D.
would like to thank the ‘‘AFAM’’ CEC Net-work for financial support.
KeyWords: Ultrasonic farce microscopy (UFM); Probing atomic force microscope cantilever; Contact deformations; Adhesion; Vibrations; Elasticity; Sample
DOI: 10.1103/PhysRevB.61.13995

Citations: 74
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