Ultra-wide Love-mode bandgaps in high-frequency thin-film surface acoustic wave phononic crystals on LiTaO3/SiC

Abstract

Thin-film surface acoustic wave (TF-SAW) phononic crystals (PnCs) are promising for manipulating gigahertz acoustic waves, but achieving wide bandgaps at high frequencies remains challenging because achieving them requires both strong acoustic confinement and efficient periodic modulation. Here, we demonstrate high-frequency TF-SAW PnCs on a LiTaO3/SiC platform and realize ultra-wide Love-mode bandgaps in the gigahertz regime. Using a 200-nm-thick 42°YX-cut LiTaO3 thin film on SiC, we systematically investigate two representative geometries: a two-dimensional triangular lattice of etched air holes and a one-dimensional groove array. Transmission-line measurements confirm pronounced suppression of Love-mode propagation over 2.64–3.31 GHz (22.5%) for the triangular-lattice PnC and 2.50–3.29 GHz (27.3%) for the 1D groove PnC, in agreement with the calculated band structures. We further clarify the geometric design trends governing the bandgap characteristics and identify deeper etching together with reduced lattice period as practical routes toward even wider bandgaps and higher operating frequencies. These results establish LiTaO3/SiC TF-SAW PnCs as a compelling platform for high-frequency, wideband acoustic wave manipulation and highlight their strong potential for next-generation integrated acoustic devices, including filters, resonators, and sensors.