Nonlinear SAW propagation in thin-film systems with residual stress

The propagation of small- and finite-amplitude surface acoustic waves (SAWs) in stressed thin-film systems is modeled. Results are presented for an initially monofrequency, plane wave traveling in the [100] direction of systems composed of either Ge (loading) or diamond (stiffening) epitaxial films under compressive stress on an unstressed [001] Si substrate. Cases are considered for both thinner and thicker films in terms of their ratios of dispersion to nonlinearity ratios. For finite-amplitude waves, comparison between unstressed and stressed films indicates that larger effects occur at longer propagation distances and for higher harmonics.