Low Temperature Gas Sensing with Novel Top-bottom Electrode Configuration

Abstract

Gas sensors based on undoped and Cr doped TiO2 layers with novel top and bottom electrode (TBE) configuration have been employed for NO2 and H2 gas sensing. The sensing layers of about 2 micro-meter thickness were sandwiched between 200 nm thick Pt top and bottom electrodes. These sensors with TBE configuration show promising gas sensing behaviour towards both oxidizing and reducing gases. The crystal structure, microstructure and chemical composition studies of the sensors were performed by X-ray diffraction technique (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), respectively. The comparative structural, morphological and compositional studies enable us to understand the effect of Cr3+ (0.755 Å) substitution within Ti4+ (0.745 Å) lattice on gas sensing properties (24°-200°C). The Cr doped TiO2 sensors were able to detect various concentrations of NO2 at 200 °C and H2 at room temperature. Response/recovery times for 90% change in sensor resistance are in the order of tens of seconds for NO2 at 200 °C and a few minutes for H2 at room temperature.