Enhancement of surface properties of sol gel tin dioxide thin films with addition of surfactant in the precursor solution

Abstract

The use of the Triton X-100 nonionic surfactant in the precursor solution has revealed a fundamental increase on the surface area, which is very relevant for applications as gas sensors and in photocatalysis. Besides, this increase aids in adhesion of the SnO2 film onto the substrate. Surfactant presence leads to an increase in the roughness (rms) from 57.6 to 275\xa0nm. The influence can also be observed in the XRD profiles, with a higher degree of crystallinity for deposited films from solutions with Triton. The surfactant inclusion decreases the defect density in the film even though it increases the electron scattering, leading to rather resistive films that are thermally excited only above room temperature. The activation energy for the defect ionization is rather high, 800\xa0meV, but the thermal excitation takes place at a lower temperature range, compared to films prepared without Triton in the solution processing. The performance on photocatalysis is improved for films prepared with Triton X-100, with most of methylene blue dye degraded in the first 90\xa0min when interacting with the sample. Combination of transparency and electrical properties of SnO2 with improved surface properties of films prepared with Triton X-100 leads to potential application in photoelectrocatalysis.