Measurement of anisotropic elastic moduli in local area by acoustic microscope (the case of cubic single crystal)

In this paper, a new method is suggested for the nondestructive measurement of elastic moduli on the local surface of an anisotropic material by an amplitude and phase acoustic microscope. It is confirmed that the anisotropic wave velocities in a local area are determined from the complex V(z)curve measured by a line-focus acoustic lens. The experimental analyses were carried out for single crystal of cubic system, (001)face of gallium arsenide, with water or mercury as the coupler. The velocity of the surface wave was clearly seen when the acoustic impedance of the coupler was smaller than that of the specimen. The velocity of the longitudinal wave was successfully measured, provided the acoustic impedance of the coupler was comparable to that of the specimen. Then, the elastic moduli in a single crystal of gallium arsenide was determined from the measured longitudinal and surface wave velocities according to elastodynamic theory. It was shown that the present method is very useful in determining the anisotropic elastic moduli of a cubic system in a local area.