Gas sensing enhancing mechanism via doping-induced oxygen vacancies for gas sensors based on indium tin oxide nanotubes

It's demonstrated that the defects induced by doping can greatly influence the sensing properties of oxide-based gas sensors. In this work, the authors have designed indium tin oxide nanotubes (ITO NTs) with different Sn doping concentrations. Results showed that the walls of ITO NTs are comprised of the formed ITO and redundant In₂O₃ nanoparticles (NPs) at low doping concentration, and the doping-induced oxygen vacancies (V_o^··S) can be tuned by Sn concentrations. Series of sensing tests to formaldehyde gas indicated that the ITO-7 NTs show the lowest working temperature (160 °C) and the highest specific response. Here, It is noted that to eliminate the influence of the coating amount of sensing performances, a concept of specific response was proposed i.e., R_air/(m–R_gas), where R_air and R_gas respectively stand for the resistances of gas sensors in the reference gas (in air this case) and in the test gas ambience, and m stands for the mass of the coated sensing materials. The decreased working temperature could be attributed to the formed In₂O₃ NPs/ITO tubular structure, and the enhanced specific response might be mainly associated with the V_o^··S. Furthermore, a possible gas sensing enhancing mechanism via V_o^··S for ITO-based gas sensors was proposed based on our results and analysis. This research would give some instructive advice to design high-performances oxide-based gas sensors via tuning the V_o^··S.