Study of the Substrate Materials and Thin Film Sensing Layer on the SAW Sensor Behaviour for VOCs

Abstract

A SAW gas sensor has been designed for the detection of volatile organic compounds (VOCs). The model was performed employing COMSOL Multiphysics software and analysis of the device was carried out in order to study the sensing behavior of the device when different substrates and different VOC gases are applied. The results indicate that, among the investigated substrates, Lithium Niobate shows the lowest total displacement with a value of $5.17\times 10^{-4}\ \mu\mathrm{m}$. The value is associated with a frequency shift value of about 233.5949 Hz and a highest SAW resonance mode at an approximated value of 855 MHz. On the other hand, Barium Sodium Niobate substrate shows the highest frequency shift value of about 281.5899 Hz. Indeed, the SAW device is simulated under the influence of several VOCs. Furthermore, investigation of the thickness of the polyisobutylene (PIB) thin film sensing layer with Lithium Niobate as a substrate shows that the frequency difference between the resonance frequency before and after applying the Dichloromethane (DCM) VOC, reaches its maximum value of ∼1650 Hz at a PIB layer thickness of about $1.4\ \mu\mathrm{m}$.