Employing the pyroelectric effect in LiTaO3 thin film for infrared detection of complex gases

Abstract

In this paper, the lithium tantalite ( LiTaO3 ) thin film has been employed as the highly sensitive element for infrared detection of compound (refrigerant) gases such as 1,1,1,2-Tetrafluoroethane ( C2H2F4 ) and 1,1,1,2,3,3,3-Heptafluoropropane ( C3F7H ). The LiTaO3 thin film was subjected to the mid-infrared light from output transmission spectra of C2H2F4 as well as C3F7H molecules used as sources. The technology for preparation of LiTaO3 thin film as well as detector design and manufacturing are presented. Particular attention was paid to production of conductive electrodes, including a very thin semitransparent Au layer evaporated on the top surface of LiTaO3 pyroelectric material. Important characteristics of the LiTaO3 based pyroelectric system are briefly discussed. Additionally, the design, construction, and performance of the gas chamber operating as a channel for gas sensor testing is briefly described. The pyroelectric open-circuit voltage generated in LiTaO3 was boosted with a signal processing circuit for selective high-sensitivity detection of compound gases at room temperature. The infrared (IR) filters such as titanium dioxide (TiO2 ) and zinc oxide ZnO having narrow bandwidth and working at a normal incidence were integrated into a compact and portable pyroelectric micro-sensor before the LiTaO3 pyroelectric element in the same package for cleaning background in a broad IR spectrum of both refrigerant gases. The performance, stability, and accuracy of fabricated LiTaO3 -based IR gas sensors operating on the pyroelectric open-circuit voltage were tested and improved. IR gas sensors designed and prepared in this study can be utilized for non-contact, sensitive, and selective detection of highly hazardous and explosive gases.