Lamb waves in an anisotropic plate of a single crystal silicon wafer

Lamb waves are dispersive in a plate and elastic properties of anisotropic materials are dependent on the crystal orientation. It is expected that the wave propagation on a thin anisotropic plate is complex due to dispersion of Lamb waves which will be dependent on the propagation direction. Therefore it is essential to understand elastic waves in an anisotropic plate. In the present work, a silicon wafer of 100 mm diameter and 0.5 mm thick with [100] direction was interrogated with leaky Lamb wave (LLW). Lamb waves were generated in a silicon wafer with the variation in incidence angles. Edge reflected LLWs were detected by the same transducer in a pulse echo set-up. In order to clarify the propagation characteristics in anisotropic plates, 2-dimensional angular profile has been proposed in the presentation. In order to predict dispersion curves of Lamb waves, longitudinal and transverse wave velocities were calculated from the static elastic constants. As results, it was found that 2 dimensional angular profile represents the crystal structures of plates. It was also found that there is unexpected peak in angular profile due to anisotropy of the silicon wafer. Measures dispersion curves in a silicon wafer were qualitatively similar to calculated ones.