高感度單埠表面聲波氣體感測器之特性研究

Characterization of Highly Sensitive One-Port Surface Acoustic Wave Sensors

何許成(Hsu-Cheng Ho)

指導教授 ： 鄭湘原

中原大學/工學院/電子工程研究所/碩士(2006年)

https://doi.org/10.6840/cycu200600778

摘要

自西元1969年起，表面聲波元件(surface acoustic wave)振盪器已廣泛的運用在軍事的毒氣、生化偵測及商業上的氣味檢測，表面聲波元件因其表面材質之質量及彈性反應機制易受物質影響，因此被運用在感測器上，感測氣體或液體的物理特性及化學特性，最常見的包含有溫度、濕度、壓力、距離、濃度、氣體種類…等等，且表面聲波元件感測器在價格上極具競爭力且具有耐用、高敏感度及穩定性佳等優點，而其他應用如無線通訊亦為其能力所及。
本論文中所敘述之一乙醇（C2H5OH）氣體感測器，主由單埠（one-port）的表面聲波諧振器配合外部線路設計，形成一表面聲波振盪器，其中心頻率與輸出功率分別為159.7MHz及12.5dB；因其利用雷利波（Rayleight wave）進行表面波傳遞，且於該表面聲波元件的表面塗佈上一層具吸附、辨識能力的聚異戊二烯（Poly isoprene）薄膜，故成為一具偵測乙醇的氣體感測器；因此當表面聲波元件曝露在乙醇（C2H5OH）氣體中時，其表面波速會改變進而引起的頻率漂移，實驗結果顯示其優異的靈敏度，足以與典型雙埠（two-port）表面聲波元件所構成的氣體感測器相比較。

關鍵字

單埠表面聲波 ； 乙醇（C2H5OH） ； 雷利波（Rayleight wave）

並列摘要

Since 1969, surface acoustic wave (SAW) oscillator have found increasing applications in a wide variety commercial and military fields. Surface acoustic wave (SAW) devices respond to the mass and elastic mechanical properties of materials on the device surface. Therefore, they can be used as sensing devices, which sense chemical and physical properties in gas and liquid forms. Their applications include temperature, humidity, pressure, distance, density, gas species and so on and so forth. Acoustic wave sensors are competitively low cost, inherently compact, relatively sensitive, and intrinsically reliable. Some of their applications are even capable of being passively and wirelessly operated.
In this thesis, we develop a C2H5OH vapor sensor incorporating with a one-port-SAW–device-based Pierce oscillator. The SAW device is coated by an absorptive film of Poly isoprene (PIP), while the surface wave propagates in Rayleigh mode. The center frequency and amplitude of the SAW device are 159.7MHz and 12.5dB, respectively. The SAW interdigital transducers (IDTs) were designed as a resonating element in the Pierce oscillator circuit whose frequency shift caused by velocity changing is characterized during its exposure to C2H5OH vapor.〔1〕 The results show an outstanding sensitivity in comparison with a conventional two-port SAW gas sensor.
The thesis comprises 6 chapters whose contents and order are carefully arranged to provide readers a basic research procedure includes mechanism of SAW device, models and characteristics, circuits design, circuits simulation, gas experiments, and the results.

並列關鍵字

Rayleigh mode ； one-port-SAW ； C2H5OH vapor sensor

參考文獻

[1] Lord Rayleigh, proc. London Math. Soc.17, 4(1885).

[3] Colin Campbell, “Surface Acoustic Wave Devices and Their Signal Processing Applications, Academic Press”, INC. 1989.

[4] R. Tancrell and M. Holland, “Surface Acoustic Wave Filters,” Proceeding of IEEE, Vol. 59, pp. 393, 1971.

[5] R. M White, F. W Vlotmer, Appl. Phys. Lett, 17. 314, 1965.

[6] R. F. Milsom, N.H.C Reilly and M. Redwood, “Analysis and Generation and Detection of Surface and Bulk Acoustic Waves by Interdigital Transducers”, 1997.