Picosecond time scale imaging of mechanical contacts

Ultrasonics. 2010 Feb;50(2):197-201. doi: 10.1016/j.ultras.2009.08.008. Epub 2009 Aug 14.

Abstract

By means of an ultrafast opto-acoustic technique we study the nanoindentation of thin chromium films on sapphire substrates using a ceramic ball bearing. Acoustic pulses at approximately 40 GHz returning from the film-indenter interface allow the film indentation profiles to be probed to sub-nanometer resolution over contact areas approximately 25 microm in radius. The deformation of the films during loading is thereby revealed. Furthermore, thermal wave imaging of the contact at megahertz frequencies is simultaneously achieved.