Surface Acoustic Waves in Z-Sections of Piezoelectric Monocrystals of Hexagonal Syngony

摘要

A new statement of the problem on the calculation of kinematic and dynamic characteristics of surface acoustic waves in piezoelectric monocrystals is proposed. A procedure for solving the above problem is also proposed with due regard for the existence of electric field scattering on the crystal surface not covered with electrodes and the vortex component of electric field in the general case.The procedure for mathematical description of surface acoustic waves at zero approximation is shown using an example of Z-section of monocrystals of hexagonal syngony. The system of eigenfunctions is built and eigenvalues are determined of the uniform boundary problem for the case of plain deformed state. The general solutions obtained for a particular case of isotropy of elastic properties of deformable solid body are reduced to the generally known definitions of the Rayleigh surface waves. The surface acoustic waves in Z-sections of ZnO and CdS monocrystals similar to the Rayleigh wave in isotropic elastic half-space are shown to exist in a narrow near-surface region, while taking into account the spread of electromagnetic field outside the limits of monocrystal on surfaces that are not covered with electrodes, and the vortex part of the electric field component made it possible to establish the fact that the vertical component of the shift vector of material particles had the maximum value at the depth of (0.15–0.2)λ rather than on the very surface of crystal. A similar peculiarity of Rayleigh waves is typical also for isotropic samples. The presence of local extremum (within 7%) is typical for the vertical component of shift vector in near-surface region having thickness 0.25λ. While penetrating inside the piezoelectric at the depth of more than 2.5 wavelength, the shift levels of material particles decrease by more than one order of magnitude.