Flexoelectricity and size effects on SH surface waves in a nanoscale piezoelectric semiconductor layered medium
Xinchang Fang, Linyao Wang, Jia Lou, Huiqing Fan, Juan Du
Abstract
As piezoelectric devices continue to miniaturize, size-dependent effects that are negligible at macroscopic scales become increasingly significant at the micro and nano levels, substantially influencing material properties and device functionality. This research investigates the dispersion characteristics of shear horizontal (SH) surface waves in a nano-scale piezoelectric semiconductor (PSC) layer perfectly bonded to an underlying elastic substrate. The governing equations for both the PSC layer and substrate, along with the boundary conditions on the free surface and the continuity conditions at the interface, are derived from Hamilton's principle. The dispersion characteristics are obtained by solving the eigenvalue problem using the genetic algorithm implemented in MATLAB. The effects of various size-dependent factors, including flexoelectric effects, micro-inertia gradient, strain gradient, and electric field gradient, on the dispersion and attenuation features of SH surface waves are investigated. Our findings demonstrate that increases in the flexoelectric coefficient and the characteristic length scale parameter related to the strain gradient lead to higher wave velocities. Conversely, increases in the characteristic length scale parameters associated with the micro-inertia gradient and electric field gradient, as well as the thickness of the PSC layer and the initial carrier density, result in reduced wave velocities. By considering these diverse size effects, this research enhances the design of surface acoustic wave (SAW) devices, expanding their applications across various advanced technologies.