This paper investigated an infrared (IR) sensitive Lateral Field Excitation (LFE) Film Bulk Acoustic Resonator (FBAR). The resonant frequency of the LFE FBAR decreased when there was IR (peak wavelength at 750nm) illumination on the device. A linear relationship between the resonant frequency and the IR intensity was obtained with a detection limit of 9 µW/mm2. The sensing mechanism is attributed to the fact that the Young''s modulus of the resonator material (ZnO) depends on temperature. In general, for a resonator operating in a bulk mode, a change in the Young''s modulus translates into a shift of the resonant frequency. Thus, the sensitivity of the FBAR relies on its temperature coefficient of resonant frequency (TCF). Thickness Field Excitation (TFE) FBAR possessed a larger TCF. However, it showed a lower sensitivity to IR compared with the LFE FBAR. This was due to the reflection of IR radiation from the top electrode on the TFE FBAR.
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机译：本文研究了对红外（IR）敏感的横向场激励（LFE）薄膜体声谐振器（FBAR）。当设备上有IR（峰值波长为750nm）照明时，LFE FBAR的谐振频率降低。共振频率与IR强度之间呈线性关系，检出限为9 µW / mm 2 。感测机制归因于以下事实：谐振器材料（ZnO）的杨氏模量取决于温度。通常，对于以体模式工作的谐振器，杨氏模量的变化转化为谐振频率的偏移。因此，FBAR的灵敏度取决于其谐振频率温度系数（TCF）。厚度场激励（TFE）FBAR具有较大的TCF。但是，与LFE FBAR相比，它对IR的敏感性较低。这是由于TFE FBAR上的顶部电极反射了IR辐射。
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