Opto-Acoustic Technique to Evaluate Adhesion Strength of Nano-Scale Systems
An opto-acoustic technique to evaluate the adhesion strength of thin film systems at the film-substrate interface is discussed. The strongly and weakly adhered film specimens are configured as the end-mirrors of a Michelson interferometer, and driven from the rear with an acoustic transducer at audible frequencies. The amplitude of the resultant oscillation of the film is quantified as the variation in the contrast of the interferometric fringe pattern observed with a digital camera at 30 frames/s. The technique successfully differentiates the adhesion strength of the specimens. Fourier analysis in the spatial frequency domain enables us to estimate the oscillation amplitude of the thin film in nanometers as a function of driving frequency.
KeywordsAdhesion Strength Oscillation Amplitude Fringe Pattern Michelson Interferometer Driving Frequency
The authors are grateful to Mark Horn of the Pennsylvania State University for helpful discussions regarding the science of thin-film coating. This study has been supported in part by the National Science Foundation International Research Experience for Student Grant (IRES-0927033) awarded to Southeastern Louisiana University, the Tokyo Denki University internal research grant and the National Research Foundation of Korea (grant No. 2011–001790).