UV-induced desorption of oxygen at the TiO2 surface for highly sensitive room temperature O2 sensing.

TiO 2 was widely considered as a promising material for gas sensing. However, developing TiO 2 based O 2 sensors working at room temperature is still challenging owing to the difficulties of desorbing oxygen adatoms from the TiO 2 surface. Here, the influence of the UV irradiation on the desorption of the surface oxygen on the TiO 2 films was investigated by using the atmosphere dependent electric transport, Kelvin probe microscopy and x-ray photoelectron spectroscopy. A lasting high conductivity and high Fermi level of the TiO 2 film were observed after the UV irradiation in vacuum, which can be drastically suppressed by a subsequent O 2 gas exposure. Thus the UV induced desorption of the surface oxygen is evidenced. Moreover a surface charge transfer model is proposed based on DFT calculations to account for the photodesorption mechanism. Utilizing such effect, the film conductivity was increased and the adsorption sites were actively recovered upon UV irradiation, thereby greatly enhanced the O 2 gas sensitivity. Our findings provided a way to optimize the performance of the O 2 sensors at room temperature with low cost and high efficiency. • TiO 2 based Chemiresistive O 2 sensor working at room was fabricated. • The conductivity and Fermi level response to the O 2 and UV was studied. • The UV induced desorption of the oxygen adatoms on TiO 2 was evidenced. • The photodesorption mechanism was clarified by the hole transfer model. • The enhancement of the sensitivity by UV irradiation was demonstrated. [ABSTRACT FROM AUTHOR]