Comparison of slowness curves of Lamb wave with elastic moduli and crystal structure in silicon wafers

[100], [110] and [111] single crystal silicon wafers are employed as specimens. Varying incident angle and rotating specimen, leaky Lamb wave (LLW) from immersed wafer were detected. Analyzing signal of LLW from various propagation directions and phase velocities of each specimen, slowness curves were obtained and they showed unique symmetry with various symmetric axis. Slowness curves were compared with elastic moduli of each wafer. They showed same symmetry as crystal structures. Also, slowness curves showed expected pattern and values that can be inferred from elastic moduli. This assures that drawing slowness curve is one way to examine crystal structures of anisotropic solids. In addition, skew symmetry of slowness curve was observed for all specimens, and it requires further discussion about crystal structure of silicon crystal.