Gigahertz-range electro-acoustic devices based on pseudo-surface-acoustic waves in AlN∕diamond∕Si structures

Abstract

Diamond and AlN are, respectively, the nonpiezoelectric and the piezoelectric materials showing the highest acoustic velocities. Consequently, pseudo-surface-acoustic waves (PSAWs) in AlN∕diamond structures exhibit the highest surface wave velocities among all known layered structures. Phase velocity dispersion curves and attenuation for PSAW propagating along this structure have been calculated for different electrical boundary conditions. An experimental delay line, designed to operate at low PSAW attenuation conditions, as predicted by theoretical results, has been implemented and tested. A good accordance between experimental results and theoretical predictions was found. It is expected that devices based on PSAW propagation in AlN∕diamond structures are suitable to operate at frequencies several times higher than those of available devices, at a given linewidth resolution limit in the transducers technology.

Super-High-Frequency SAW Resonators on AlN/Diamond

“…In addition, the theoretical values of K 2 were calculated using the transfer matrix approach [15]. The material parameters used are listed elsewhere [16]. Fig.…”

P3O-7 Theoretical Investigation of PSAW Generation and Propagation in AlN/Isotropic Diamond/Si Structure

“…Using our computer software, we analyzed the PSAW propagation along AlN/diamond/Si structures, using the material data from [9,10] for the hexagonal 6mm AlN film and for the isotropic poly-crystal diamond film. For the single crystal Si substrate the following material data were used: c 11 , c 12 and c 44 : 166.0, 63.9 and 79.6 GPa, respectively; ε 11 : 106.2 pF/m and ρ: 2330.0 kg/m 3 [22].…”

“…is considered for the acoustic modes, being the complex variable V S defined as the inverse of the projection of the complex slowness vectors of the partial waves, forming the PSAW [9] at the surface of the layered structure. Calculations have been performed at low attenuations of the acoustic modes ( )…”

“…One way to increase work frequencies is to use high acoustic velocity materials, such as silicon, sapphire or diamond [1][2][3][4][5]. Among piezoelectric films used for acoustic wave excitation, AlN is a promising candidate, for diamondbased SAW devices [6][7][8][9][10]. Aiming to the higher limit of frequencies, there is a large body of research devoted to pseudo-surface-acoustic waves (PSAWs) with phase velocities around 40% higher than those of SAWs [7][8][9][10][11][12].…”

“…The measured insertion loss for the PSAW mode in a AlN/isotropic diamond structure was less than 70 dB over a propagation length of ~400λ (loss < 0.2dB/λ, including energy conversion in the IDTs). When the partial waves to construct the PSAW solution are selected from the inhomogeneous shear wave, carrying away the energy from the surface, and the longitudinal wave, where the Poynting vector is directed to the surface, two conditions where found, where the PSAW solution degenerates into a SAW solution which does not show the infinite in the energy flow ( Fig.1) [9]. It should be noted that these solutions are located rather far from the branch points (the points where BAWs rise), so SAWs are well defined, that is the main part of the acoustic energy is confined within a depth of ~ 1 λ.…”