5 GHz Shear-Horizontal Wave Micro-Mass Sensing

Surface acoustic wave (SAW) micro-mass sensors have garnered significant attention due to their versatile applications in medical measurements, industrial production quality control, and environmental pollution monitoring. Traditional devices of this kind often grapple with the predicament of operating at low frequencies, typically below 2 GHz, and relying on the Rayleigh sensing mode. This can undermine their capability for highly sensitive detection. Herein, we present the manufacture and application of a high-frequency SAW micro-mass sensor based on a LiTaO3/SiO2/Si heterostructure, demonstrating superior frequency capability in the range of 1–10 GHz, achieved through electron beam lithography (EBL). Different acoustic modes and their micro-mass sensitivity were thoroughly analyzed using finite element analysis, revealing that the shear-horizontal (SH) wave exhibited superior performance and the highest mass sensitivity among the analyzed modes, which was also confirmed by the experiments. To evaluate the exceptional sensing ability, the SH wave (up to ~5 GHz) was successfully implemented in an SAW micro-mass sensor for Al film and SiO2 film micro-mass detection, exhibiting an ultramass sensitivity of 14 370 and 13181.8 MHz
$\cdot $
mm2/
$\mu \text{g}$
, respectively. In a smoke concentration detection application, the high-frequency SAW devices (4.83 GHz) exhibited a sensitivity approximately 129 times higher than that of low-frequency SAW devices (195.5 MHz) in the same testing environment, verifying the advantages of high sensitivity. This study introduces a viable strategy for constructing high-sensitivity SAW micro-mass sensors.