Materials Research Express (Jan 2024)
Employing the pyroelectric effect in LiTaO3 thin film for infrared detection of complex gases
Abstract
In this paper, the lithium tantalite ( ${{\rm{LiTaO}}}_{3}$ ) thin film has been employed as the highly sensitive element for infrared detection of compound (refrigerant) gases such as 1,1,1,2-Tetrafluoroethane ( ${{\rm{C}}}_{2}{{\rm{H}}}_{2}{{\rm{F}}}_{4}$ ) and 1,1,1,2,3,3,3-Heptafluoropropane ( ${{\rm{C}}}_{3}{{\rm{F}}}_{7}{\rm{H}}$ ). The ${{\rm{LiTaO}}}_{3}$ thin film was subjected to the mid-infrared light from output transmission spectra of ${{\rm{C}}}_{2}{{\rm{H}}}_{2}{{\rm{F}}}_{4}$ as well as ${{\rm{C}}}_{3}{{\rm{F}}}_{7}{\rm{H}}$ molecules used as sources. The technology for preparation of ${{\rm{LiTaO}}}_{3}$ 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 ${{\rm{LiTaO}}}_{3}$ pyroelectric material. Important characteristics of the ${{\rm{LiTaO}}}_{3}$ 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 ${{\rm{LiTaO}}}_{3}$ 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 $({{\rm{TiO}}}_{2}$ ) and zinc oxide $\left({\rm{ZnO}}\right)$ having narrow bandwidth and working at a normal incidence were integrated into a compact and portable pyroelectric micro-sensor before the ${{\rm{LiTaO}}}_{3}$ 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 ${{\rm{LiTaO}}}_{3}$ -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.
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