Modelling of simultaneously obtained small and wide angle synchrotron-radiation scattering depth profiles of ordered titania nanotube thin films

Abstract

Thin-films of vertically aligned titanium dioxide nanotubes are key constituents of charge transfer layers in 3rd generation photovoltaics. The beneficial charge transport primarily occurs due to the favourable microstructural features, i.e. the large effective surface-to-volume ratio. Here measuring methods are selected which are sensitive to microstructural features: Simultaneous Grazing Incidence Small and Wide Angle X-Ray Scattering (GISWAXS) and Scanning Electron Microscopy (SEM). Further, a model is developed for the simulation and explanation of the GISWAXS experimental data. Titanium nanotube arrays were investigated, which were previously successfully produced by electrochemical anodization of titanium thin film evaporated onto a zinc-oxide coated glass substrate. The developed model was shown to be appropriate to describe the obtained samples, which consist of arrays of single nanotubes with a diameter of 40–80 nm, and a titanium dioxide layer with a porosity of 30–50%. Within this work, we presented simultaneous GISWAXS as a comparable tool to SEM for the fast and successful study of the average nanotubes’ diameters in nanotubes arrays.