Publication

Abstract : The current work reports the room temperature sensing of CO2 by growing Si-incorporated TiO2 thin films on Si-substrate with enhanced sensing response. The study suggests that the incorporation of SiO2 in TiO2 lattice can be used to manipulate its defect states which alter the electrical conductivity of TiO2 from n-type to p-type. The TiO2 and Si-incorporated TiO2 thin films are grown on Si-substrate at 250 °C by VLS method. FESEM images confirm the formation of a continuous film and the XRD analysis of such thin films indicates transformation of crystalline anatase TiO2 to amorphous nature upon Si incorporation. The incorporation of Si within TiO2 also results in the formation of oxygen related vacancy states along with the reduction of Ti related vacancies within the TiO2 lattice. Such defect states have been investigated by performing absorption spectroscopy, room temperature PL measurements and XPS analysis. The 50% Si-incorporated TiO2 thin film is observed to provide a sensing response of 198% at 200 sccm CO2 flow rate which is only 2.54% for TiO2 thin film when measured at room temperature with ~ 47% relative humidity. However, such room temperature sensing response decreases with the increase of relative humidity and found to be 73% when the relative humidity is increased to 85%. Furthermore, such Si-incorporated TiO2 sensors exhibit a fast response and recovery time of 5.7 s and 3.6 s, respectively. Therefore, the 50% Si-incorporated TiO2 thin film-based sensors can be efficiently used for room temperature CO2 sensing by utilizing a simple cost-effective fabrication technique.