Detection of Molecular Films by Harmonic Generation of Surface Acoustic Waves

Abstract

We have applied the technique of thin film detection by harmonic generation of dispersive Rayleigh waves to detect molecular layers of stearic acid and Ti diffused layers on LiNbO3 substrates. The technique is based on the loading of a thin film on an ideal substrate which causes the velocity dispersion between the fundamental of a Rayleigh wave and its second harmonic. This dispersion causes sinusoidal oscillation of the second harmonic intensity as a function of interaction length. Using an optical probe to measure the diffracted light by the surface wave second harmonic along the propagation direction, the velocity variation between the fundamental and the second harmonic due to the film can easily be measured. © 1977 The Japan Society of Applied Physics.