Surface acoustic wave based ozone sensor with an InOx/Si3N4/36° YX LiTaO3 structure

A layered Surface Acoustic Wave (SAW) device based on an InOx/Si3N4/36° YX LiTaO3 structure is investigated for sensing ozone in air at different operating temperatures and concentrations. These concentrations are between 25 ppb and 150 ppb. Layered SAW devices are of a great interest as they show a remarkable performance for liquid and gas sensing applications. This structure is a single delay line SAW device with 64 input and output finger pairs, having periodicity of 24 μm. They were fabricated on a 36° Y-cut X-propagating lithium tantalate (LiTaO3) piezoelectric substrate. A 1 μm thick silicon nitride (Si3N4) layer was deposited over the finger pairs and a 100 nm indium oxide (InOx) sensing layer was deposited over the Si3N4 layer. Both layers were deposited by RF magnetron sputtering. InOx was chosen as it has a remarkable sensitivity towards ozone. Si3N4 was chosen as it is inert and has stable characteristics at high temperature. The sensor performance is analysed in terms of response time, recovery time and response magnitude as a function of operational temperature. The operational temperature ranges between 185°C and 205°C. The sensor shows repeatability, reversibility, fast response and recovery time. At approximately 190°C the highest sensitivity was observed. A frequency shift of 5.0 kHz at 25 ppb, 6.5 kHz at 50 ppb ozone was recorded. The presented results show this structure is promising for gas sensing applications.

[1]  Colin Campbell,et al.  Surface Acoustic Wave Devices for Mobile and Wireless Communications , 1998 .

[2]  H. Fritzsche,et al.  Reversible changes of the optical and electrical properties of amorphous InOx by photoreduction and oxidation , 1994 .

[3]  David C. Stone,et al.  Surface-Launched Acoustic Wave Sensors: Chemical Sensing and Thin-Film Characterization , 1997 .

[4]  Robert Weigel,et al.  LSAW attenuation in double-layer-systems , 1999, Proceedings of the 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symposium (Cat. No.99CH36313).

[5]  V. Cimalla,et al.  The influence of deposition parameters on room temperature ozone sensing properties of InOx films , 2001 .

[6]  Jay W. Grate,et al.  Acoustic Wave Sensors , 1996 .

[7]  T. S. Hickernell,et al.  The elastic properties of thin-film silicon nitride , 1990, IEEE Symposium on Ultrasonics.

[8]  Raymond E. Dessy,et al.  Surface acoustic wave probe for chemical analysis. I. Introduction and instrument description , 1979 .

[9]  M. P. D. Cunha,et al.  Pseudo and high velocity pseudo SAWs , 2000 .

[10]  Wojtek Wlodarski,et al.  Low-temperature InOx thin films for O3 and NO2 gas sensing , 2003, SPIE Microtechnologies.

[11]  Dae-Sik Lee,et al.  Environmental gas sensors , 2001 .

[12]  Jordi Arbiol,et al.  In2O3 films deposited by spray pyrolysis as a material for ozone gas sensors , 2004 .

[13]  Norio Miura,et al.  PREPARATION OF INDIUM OXIDE THIN FILM BY SPIN-COATING METHOD AND ITS GAS-SENSING PROPERTIES , 1998 .

[14]  Michael J. Vellekoop,et al.  Acoustic wave sensors and their technology , 1998 .

[15]  Tadashi Takada,et al.  Highly sensitive ozone sensor , 1993 .

[16]  Per Kofstad,et al.  Nonstoichiometry, diffusion, and electrical conductivity in binary metal oxides. , 1972 .

[17]  B. Drafts.  Acoustic wave technology sensors , 2001 .

[18]  Giorgio Sberveglieri,et al.  Electrical and structural properties of RGTO-In2O3 sensors for ozone detection , 1999 .

[19]  M. Ivanovskaya,et al.  Mechanism of O3 and NO2 detection and selectivity of In2O3 sensors , 2001 .

[20]  V. Cimalla,et al.  InO X THIN FILMS, CANDIDATES FOR NOVEL CHEMICAL AND OPTOELECTRONIC APPLICATIONS , 2000 .

[21]  David S. Ballantine,et al.  Acoustic wave sensors : theory, design, and physico-chemical applications , 1997 .

[22]  Wojtek Wlodarski,et al.  Investigation on ozone-sensitive In2O3 thin films , 1999 .

[23]  Udo Weimar,et al.  Development of Modular Ozone Sensor System for application in practical use , 2000 .

[24]  V. Cimalla,et al.  InOX THIN FILMS , CANDIDATES FOR NOVEL CHEMICAL AND OPTOELECTRONIC APPLICATIONS , 2000 .

[25]  Raymond E. Dessy,et al.  Surface acoustic wave probes for chemical analysis. II. Gas chromatography detector , 1979 .