Micromachined surface acoustic wave sensor for detecting inert gases

S. Ahuja, M. Hersam, C. Ross, H. T. Chien, A. C. Raptis

Research output: Contribution to journalConference article

Abstract

Surface acoustic wave (SAW) sensors must be specifically designed for each application because many variables directly affect the acoustic wave velocity. In the present work, we have designed, fabricated, and tested an SAW sensor for detection of micromachined interdigitated transducers (IDTs) and delay lines fabricated by photolithography on a single Y-cut LiNbO3 substrate oriented for Z-propagation of the SAWs. One set is used as a reference and the other set employs a delay line coated with a titanium-based thin film sensitive to electrical conductivity changes when exposed to metastable states of He. The reference sensor is used to obtain a true frequency translation in relation to a voltage controlled oscillator. An operating frequency of 109 MHz has been used, and the IDT finger width is 8 μm. Variation in electrical conductivity of the thin film at the delay line due to exposure to He is detected as a frequency shift in the assembly, which is then used as a measure of the amount of metastable He exposed to the sensing film on the SAW delay line. A variation in the He pressure versus frequency shifts indicates the extent of the metastable He interaction.

Original languageEnglish
Pages (from-to)435-438
Number of pages4
JournalProceedings of the IEEE Ultrasonics Symposium
Volume1
Publication statusPublished - Dec 1 1996
EventProceedings of the 1996 IEEE Ultrasonics Symposium. Part 2 (of 2) - San Antonio, TX, USA
Duration: Nov 3 1996Nov 6 1996

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

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