Rayleigh wave reflection from single surface imperfections on isotropic substrates

Abstract

Rayleigh surface waves propagating in (111) Si substrate decorated with Ni phononic nanostructure AIP Conf.The specific features of the Rayleigh wave reflection from single surface imperfections of an isotropic substrate are studied by the finite element method. Six types of the imperfections are considered, namely, upstep and downstep, projection and groove, and strip of foreign material coating the substrate and buried into it. The dependence is found and analyzed of the absolute value and the phase of the reflection coefficients on the geometrical parameters of defects and the angle of incidence. Numerical results are compared to analytical predictions based on a development of the reflection coefficient in powers of the defect height to wavelength ratio h / and limited to the first-order term. In particular, this comparison reveals that in some cases approximate expressions are able to provide a good precision. At the same time situations are met when the linear approximation fails to describe the behavior of the reflection coefficient even at fairly small h / .

SAW resonance excitation of acoustic strip waveguide modes

“…The reflection and the transmission coefficients are found by the spacial Fourier transform of the displacement field on the free surface of the substrate. Our estimations yield that the error in the determination of these coefficients does not exceed 2-3% (see [3]- [8] for more detail). The resonant reflection is considered for the Z-cut of AlN (symmetry 6mm).…”

Surface acoustic wave reflection/transmission at vertical borders of piezoelectric substrates

“…These amplitudes are calculated, like in our earlier papers [28][29][30][31][32][33], with the help of the spacial Fourier transform by extracting the harmonic k x ¼ Àk I of the displacement u SC;z ðr; tÞ at z ¼ 0 and the harmonic k z ¼ Àk T of the displacement u SC;x ðr; tÞ at x ¼ 0, respectively. The reflection and the transmission coefficients are defined as the ratio of the normal component of the mechanical displacement of the corresponding wave to the normal component of the mechanical displacement of the incident SAW.…”

SAW reflection from surface inhomogeneities of isotropic and anisotropic substrates

“…If the substrate is isotropic, then the electric potential is merely left from considerations. [A more detailed discussion is presented in [8], [9].] According to [1], the coefficients R An for the upstep and the downstep differ only by sign.…”

“…Let us compare the reflection coefficient from a single electrode found directly by FEM with the reflection coefficient R com per electrode calculated by Eq. (8). The edge frequencies are obtained with the help of computations for the infinite grating.…”