Influence of surface stress and atomic defect generation on Rayleigh wave propagation in laser-excited solids

The surface stress effects on the Rayleigh wave propagation characteristics in solids with distributions of laser-induced atomic defects (vacancies, interstitial atoms) are studied. Defect-density fields are governed by the strain-induced generation, recombination and diffusion of atomic defects. Formulation of the general surface wave propagation problem has been made, and the corresponding frequency equation has been derived and analyzed. Some important frequency equations, as obtained by other authors, have been deduced as special cases from the frequency equation for Rayleigh waves. The combined effects of surface stress and defect density field on the Rayleigh wave velocities are shown by numerical calculations and graphs. It is found that the Rayleigh waves are generally dispersive; and in the case of low frequency with residual surface tension, a critical wave length exists, below which the propagation of Rayleigh waves is not possible. This critical wave length depends on both the residual stress and the defect distribution.