X-ray imaging of acoustic wave interaction with dislocations

We used stroboscopic X-ray topography to visualize the propagation of high-frequency (580 MHz), short wavelength (6 μm) surface acoustic waves in LiNbO3 crystals. The images showed well-resolved individual acoustic wave fronts as well as their distortions caused by scattering on linear dislocations. The observed wave front shapes indicate that a considerable portion of acoustic energy flows along a dislocation line, providing forced vibration of the dislocation string and re-emission of the secondary elastic waves. We also found that the linear dislocations, situated perpendicular to the crystal surface, produce characteristic Fresnel zone contrast in the X-ray images due to an interference of the secondary elastic waves re-emitted by the vibrating dislocations.