Investigation of sensing properties of sol–gel processed 4 at%Sb:SnO2/TiO2 thin films

Abstract

In this work we investigate the gas and photo sensing properties of the antimony doped tin oxide and titanium oxide (4 at%Sb:SnO2/TiO2) nanocrystalline thin films deposited by sol–gel dip-coating. Photoconductivity measurements are carried out under solar light spectra irradiation at different powers. These results show a photo sensitivity of the films in a lateral junction due to interfacial defects. Gas sensitivity was studied at different pressures, and higher conductivity is presented at lower pressure compared to oxygen-rich atmosphere. It occurs due to absence of oxygen adsorption on the semiconductors surface. TiO2 films are also investigated concerning its properties to gas sensing under photo-excitation with InGaN LED light source with wavelength centered in 450 nm. The decay of photo-induced current evaluated under O2 and vacuum atmospheres shows that the sample illumination may contribute to higher gas-sensitivity. This measurement allows determining the charge carrier capture energy, that is related to trapping dominated by distinct defects in each atmosphere.