UV-assisted room-temperature chemiresistive NO2 sensor based on TiO2 thin film

• We report a TiO2 based NO2 sensor that works at room-temperature under UV-illumination.
• The rf-sputtered and annealed TiO2 thin-film contained predominantly anatase phase.
• The NO2 sensor shows relatively short response time with broad detection range.
• Modulation of surface-adsorbed oxygen concentration is proposed as the sensing mechanism.

TiO2 thin film based, chemiresistive sensors for NO2 gas which operate at room temperature under ultraviolet (UV) illumination have been demonstrated in this work. The rf-sputter deposited and post-annealed TiO2 thin films have been characterized by atomic force microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction to obtain surface morphology, chemical state, and crystal structure, respectively. UV–vis absorption spectroscopy and Tauc plots show the optical properties of the TiO2 films. Under UV illumination, the NO2 sensing performance of the TiO2 films shows a reversible change in resistance at room-temperature. The observed change in electrical resistivity can be explained by the modulation of surface-adsorbed oxygen. This work is the first demonstration of a facile TiO2 sensor for NO2 analyte that operates at room-temperature under UV illumination.