Investigation of structural and optical properties of Ytterbium modified tin oxide thin films for gas sensing application

摘要

Among the various semiconducting oxides, tin oxide (SnO_2) occupies a significant position as a gas sensor. Doping has been proved to be one of the most effective ways to enhance the properties of gas sensing by altering the structure and grain size or introducing an impurity level and surface defects. Rare earth metals are good catalysts, directly active for oxidation and therefore modify surface reactivity and adsorption/desorption properties of gas sensing materials. In the present work, spray pyrolyzed SnO_2 thin films doped with Ytterbium (Yb) are prepared and its structural and optical properties are investigated. X-ray diffraction (XRD) analyses are administered which suggests that the addition of Yb promote the crystalline growth profile leading to preferential orientation. The Field Emission Scanning Electron Micrograph (FESEM) reveals the aggregate pattern of the grain distribution of SnO_2 with an average grain size of about 40 nm. The investigation of LPG sensing properties evidences that the addition of 0.6 wt. % Yb in SnO_2 enhances the sensor response to 94.5 %. The UV-Visible absorbance spectra of the samples are recorded and analyzed for identifying the defect levels introduced via doping. The probing of Photoluminescence (PL) spectra reveal the presence of oxygen vacancies in the sensor samples. From the studies, it has been confirmed that preferential orientation along with different kinds of oxygen vacancies play an important role in improving the gas sensing action.