High-frequency surface acoustic wave devices based on LiNbO3∕diamond multilayered structure

Abstract

This research is focused on the development of a new technology for the fabrication of high-frequency surface acoustic wave (SAW) filters based on diamond and lithium niobate (LiNbO3) materials. LiNbO3 films are in situ deposited at 490 °C on polycrystalline diamond substrates by radio-frequency magnetron sputtering; a multistep growth process is proposed to deposit oriented LiNbO3 films with a smooth surface. Conventional interdigital transducers are fabricated on top of the piezoelectric LiNbO3 layer by standard optical lithography. We report experimental results for a SAW bandpass filter operating at a frequency above 2.30 GHz. We have observed that Rayleigh SAW modes are excited within this structure, with extremely high phase velocities (up to 12000m∕s). This latter result illustrates the greatest advantage of using diamond as an acoustic substrate. It allows the fabrication of SAW devices operating in the gigahertz frequency range using standard optical lithography.

Relaxor-based ferroelectric single crystals: Growth, domain engineering, characterization and applications

“…Lithium niobate (LiNbO 3 ) and lithium tantalite (LiTaO 3 ) single crystals have stable ferroelectric single domain structure (3 m point group symmetry) after being poled and possess excellent temperature stability because of their high Curie temperatures (1210 °C for LiNbO 3 and 630 °C for LiTaO 3 ) [38,39]. Therefore, they have been widely used for surface acoustic wave (SAW) devices [40,41]. However, their piezoelectric constants and electromechanical coupling factors are much lower than those of BaTiO 3 materials [42,43].…”

Structural, electrical and piezoelectric properties of LiNbO3 thin films for surface acoustic wave resonators applications

“…Among those materials having interesting electro-optic and piezoelectric coefficients, lithium niobate (LiNbO 3 ) is a good candidate for coupling with NCD substrates. Recent studies have demonstrated its ability to be integrated in various opto-electronic and acoustooptic devices, such as filters [7], electro-optic modulators [8] or optical waveguides [9]. One of the main challenges is the growth of a uniform, smooth and well-oriented LiNbO 3 layer, to allow the diamond-based SAW to propagate.…”

mm-band surface acoustic wave devices utilizing two-dimensional boron nitride

“…The fundamental resonance frequency (f r ) is determined by f r = v SAW /λ, where v SAW is the speed of acoustic wave propagation at the surface, and this surface acoustic wave mode is called Rayleigh mode. LiNbO 3 [9][10][11] , LiTaO 3 12 , ZnO [3][4][5][13][14][15] , AlN [16][17][18][19] , and AlScN 20,21 are the piezoelectric materials commonly used or actively studied.…”