Surface-grating-induced zone folding and hybridization of surface acoustic modes

Brillouin light scattering measurements of surface acousta modes propagating in an ion-milled holographic grating on a Si(001) wafer have revealed clear evidence of hybridization between the Rayleigh wave and the longitudinal resonance which leads to an unexpected gap. Other new acoustic features include the folding of the Rayleigh wave about the first two zone boundaries associated with the grating, band gaps which increase with zone number, and different propagation velocities parallel and perpendicular to the grating.