Rational surface modification of ZnO with siloxane polymers for room-temperature-operated thin-film transistor-based gas sensors

High demands for and rapid development of technologies related to the Internet of Things (IoT) call for a pertinent technological breakthrough in sensing devices to effectively detect various external stimuli or target analytes. Advanced sensing platforms utilizing thin-film transistors (TFTs) are essential for realizing cost-effective and high-performance chemical sensors. Here, it is reported that the utilization of a gas-selective layer based on polymeric chromatographic stationary phases is an unprecedented and facile method to establish simultaneously the desired gas selectivity and responsivity of ZnO thin films at room temperature. With the aid of computational studies, in-depth analysis and comparison of gas-sensing and the charge transfer mechanism between the gas and the resulting sensor devices are performed. ZnO with cyanopropylmethyl-phenylmethyl polysiloxane films provide excellent selective sensing with gas mixtures, and the achieved response to vaporized ethanol is nearly three times higher than the response of pristine ZnO at ~22 °C and atmospheric pressure. This effective enhancement of sensing performance under ambient conditions is attained through the transition from chemisorption to physisorption based on intermolecular interactions between gas molecules and gas-selective polymers. This work demonstrates a potent yet cost-effective method to fabricate low power consumption gas sensor systems based on metal oxide TFT.