Comparative study of surface acoustic wave based hydrogen sensors with: InO x /SiN x /36° YX LiTaO 3 structure

Abstract

Layered Surface Acoustic Wave (SAW) based sensors with: InO x / SiN x / 36 o YX LiTaO 3 structure were developed for sensing different hydrogen (H 2 ) concentrations between 0.06% (600ppm) and 1% H 2 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 (LiTaO 3 ) piezoelectric substrate forming the input and output Interdigital Transducers (IDTs). A 1 µm thick silicon nitride (SiN x ) 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 (InO x ) deposited by r.f. magnetron sputtering provides the selectivity towards hydrogen. The highest sensitivity for the sensor with r.f. magnetron sputtered SiN x intermediate layer was recorded at 190° C, when the frequency shift of 361 KHz for 1% H 2 in synthetic air was recorded. However larger responses were obtained for the sensor with the PECVD SiN x intermediate layer at 290° C, when the large frequency shift of 516 KHz was recorded for the same H 2 concentration. Microstructural characterization of the InO x and SiN x films by Atomic Force Microscopy (AFM) and XRay Photoelectron Spectroscopy (XPS) is also presented.

Pd Nanoparticles and Thin Films for Room Temperature Hydrogen Sensor

“…Recently, H 2 sensors have gained increased interest due to its application in many significant areas. Various methods have been reported for the development of H 2 sensors based on metal-oxide [ 4 , 5 ], nanowires [ 6 , 7 ], acoustic wave [ 8 , 9 ], thin film metal and semiconductor [ 10 , 11 ]. Most of the approaches utilize Pd as a catalyst, since Pd has great affinity towards H 2 absorption [ 12 - 14 ].…”