Surface acoustic wave (SAW) devices are widely used for physical, chemical, and biological sensing applications, and their sensing mechanisms are generally based on frequency changes due to mass-loading effects at the acoustic wave propagation area between two interdigitated transducers (IDTs). In this paper, a new sensing mechanism has been proposed based on a significantly enhanced mass-loading effect generated directly on Au IDT electrodes, which enables significantly enhanced sensitivity, compared with that of conventional SAW devices. The fabricated ultrahigh-frequency SAW devices show a significant mass-loading effect on the electrodes. When the Au-electrode thickness increased from 12 to 25 nm, the Rayleigh mode resonant frequency decreased from 7.77 to 5.93 GHz, while that of the higher longitudinal leaky SAW decreased from 11.87 to 9.83 GHz. The corresponding mass sensitivity of 7309 MHz·mm²·μg^–1 (Rayleigh mode) is ∼8.9 × 10¹¹ times larger than that of a conventional quartz crystal balance (with a frequency of 5 MHz) and ∼1000 times higher than that of conventional SAW devices (with a frequency of 978 MHz). Trinitrotoluene concentration as low as 4.4 × 10^–9 M (mol·L^–1) can be detected using the fabricated SAW sensor, proving its giant mass-loading effect and ultrahigh sensitivity.

中文翻译：

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在电极上具有巨大质量负载效应的超高频表面声波传感器。

表面声波（SAW）器件广泛用于物理，化学和生物传感应用，其传感机制通常基于频率变化，这是由于两个叉指换能器（IDT）之间的声波传播区域处的质量负载效应引起的。在本文中，基于显着增强的直接在Au IDT电极上产生的质量负载效应，提出了一种新的传感机制，与传统的SAW器件相比，它可以显着增强灵敏度。所制造的超高频声表面波器件在电极上显示出显着的质量负载效应。当金电极厚度从12 nm增加到25 nm时，瑞利模式共振频率从7.77 GHz降低到5.93 GHz，而纵向漏泄声表面波的较高共振频率从11.87降低到9。83 GHz。相应的质量灵敏度为7309 MHz·mm² ·μg ^–1（瑞利模式）比传统石英晶体天平（频率为5 MHz）大约8.9×10 ¹¹倍，比传统SAW器件天平（频率为978 ）大约1000倍MHz）。使用制造的声表面波传感器可检测到三硝基甲苯浓度低至4.4×10 ^–9 M（mol·L ^–1），证明了其巨大的质量负载效应和超高灵敏度。