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5 January 2006 Comparative study of surface acoustic wave based hydrogen sensors with: InOx/SiNx/36° YX LiTaO3 structure
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Layered Surface Acoustic Wave (SAW) based sensors with: InOx / SiNx / 36° YX LiTaO3 structure were developed for sensing different hydrogen (H2) concentrations between 0.06% (600ppm) and 1% H2 in synthetic air. This paper presents a comparative study of the sensors performances in terms of response time, recovery time and response magnitude as a function of operational temperature. The SAW devices consist of metal interdigitated electrodes fabricated on lithium tantalate (LiTaO3) piezoelectric substrate forming the input and output Interdigital Transducers (IDTs). A 1 μm thick silicon nitride (SiNx) intermediate layer was deposited over these finger pairs, either by Plasma Enhanced Chemical Vapour Deposition (PECVD) or by r.f. magnetron sputtering. A 100 nm thin film of indium oxide (InOx) deposited by r.f. magnetron sputtering provides the selectivity towards hydrogen. The highest sensitivity for the sensor with r.f. magnetron sputtered SiNx intermediate layer was recorded at 190° C, when the frequency shift of 361 KHz for 1% H2 in synthetic air was recorded. However larger responses were obtained for the sensor with the PECVD SiNx intermediate layer at 290° C, when the large frequency shift of 516 KHz was recorded for the same H2 concentration. Microstructural characterization of the InOx and SiNx films by Atomic Force Microscopy (AFM) and X-Ray Photoelectron Spectroscopy (XPS) is also presented.
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Alexandru C. Fechete, Wojtek Wlodarski, Kourosh Kalantar-zadeh, Anthony S. Holland, Jarek Antosziewski, Saulius Kaciulis, and Luca Pandolfi "Comparative study of surface acoustic wave based hydrogen sensors with: InOx/SiNx/36° YX LiTaO3 structure", Proc. SPIE 6035, Microelectronics: Design, Technology, and Packaging II, 603517 (5 January 2006);

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