Piezoelectric-Layered Structures Based on Synthetic Diamond

Abstract

Resuρts oλ theoreticaρ, modeρinμ, and exυerimentaρ investiμation oλ microwave acoustic υroυerties oλ υiezoeρectric ρayered structure Me /"ρN/Me / diamond have been υresented within a wide λreφuency band . -GHz. The hiμhest amonμ πnown materiaρ φuaρity υarameter Q × f ~ Hz λor the IIa tyυe synthetic diamond at oυerationaρ λreφuency ~ GHz has been λound. Conditions oλ UHF excitation and υroυaμation oλ the buρπ, surλace, and Lamb υρate acoustic waves have been estabρish-ed and studied exυerimentaρρy. Freφuency deυendencies oλ the imυedance and φuaρity λactor have been studied to obtain a number oλ υiezoeρectric ρayered structure υarameters as eρectromechanicaρ couυρinμ coeλλicient, eφuivaρent circuit υarameters, etc. Resuρts oλ Γ λinite eρement modeρinμ oλ a μiven υiezoeρectric ρayered structure have been comυared with the exυerimentaρ ones obtained λor the reaρ hiμh-overtone buρπ acoustic resonator. "n oriμin oλ hiμh-overtone buρπ acoustic resonator's sυurious resonant υeaπs has been studied. Resuρts on UHF acoustic attenuation oλ IIa-tyυe synthetic sinμρe crystaρρine diamond have been υresented and discussed in terms oλ "πhiezer and Landau-Rumer mechanisms oλ υhonon-υhonon interaction. Identiλica-tion and cρassiλication oλ Lamb waves beρonμinμ to severaρ branches as weρρ as disυersive curves oλ υhase veρocities have been executed. Necessity oλ introducinμ a more correct Lamb-mode cρassiλication has been recoμnized.

Application of Thin Piezoelectric Films in Diamond-Based Acoustoelectronic Devices

“…Detailed study of microwave acoustic properties of diamond-based HBARs realized by aluminum nitride and aluminum-scandium nitride piezoelectric films has been fulfilled by a set of the samples. Topology of the top and bottom electrodes as well as piezoelectric film areas was especially developed to be convenient for an investigation of temperature dependences of HBAR's acoustic parameters within a wide range from 4 up to 400 K. Investigated HBARs based on PLSs differing the material of piezoelectric films and substrate thickness have demonstrated the close magnitudes of quality factor Q~11,000-12,000 which corresponded to comparatively high-quality parameter QÁf~4.2Á10 13 Hz at 3500 MHz. As a main result, one can emphasize that the application of aluminum-scandium nitride as a piezoelectric material has resulted in a drastic increase of the effective electromechanical coupling coefficient up to 2.5 times in comparison with that in aluminum nitride.…”

“…Earlier [13,14], we have successfully applied the 2D FEM simulation in order to obtain a quite complex pattern of dispersive dependences of phase velocities of plate Lamb waves observing visualization of the fields of elastic displacements belonging to a lot of acoustic modes with a number of eigenfrequencies. Besides of Lamb waves, the BAW and SAW modes of Rayleigh type were found.…”

“…(8)-(13)) form a system of equations as 10Â10 dimensions, the solution of which makes it possible to determine the amplitudes of the elastic waves in all the layers and the PLS frequency characteristics. Note that the part of the boundary condition matrix as 7Â7 dimensions allows to obtain the so-called form factor of HBAR including into calculation a traveling acoustic wave only, i.e., without taking into account the lower boundary of the crystalline substrate (12) and (13). Additionally, when Eq.…”

Features of the Metallization Influence on Phase Velocities of Acoustic Waves in Piezoelectric Plates

“…1, a). The boundary conditions, in particular, for the "Me/Piezoelectric/Me" three-layer structure are: the equality to zero of normal components of the stress tensor at the "metal/vacuum" interface; the normal components equality of the stress tensor, the equality of the displacement vectors and the equality to zero of the electric potential wave at the "metal/piezoelectric" interface [10]:…”

Metal Layer Thickness Influence on the Dispersion Characteristics of Acoustic Waves in the Layered Structure

“…The boundary conditions, in particular, for the four-layered structure "metal/piezoelectric/metal/dielectric substrate" (Fig. 1, a) are: the normal components of stress tensor at the metal/vacuum interface are equal to zero; equality of the normal components of a stress tensor at the metal/piezoelectric interface, the equality of displacement vectors and zero wave potential [13]:…”