Electronic structure changes of TiO2 thin films due to electrochromism

Titanium dioxide thin films were deposited by metal-organic chemical vapor deposition (MOCVD) on soda-lime and indium tin oxide (ITO) coated glass substrates at 400 °C. X-ray diffraction (XRD) studies revealed that the deposited films have a pure anatase phase. Thickness of the film was measured by scanning electron microscopy (SEM). Atomic force microscopy was used to study the morphology of the deposited films. Depth profiling was monitored by using secondary ion mass spectroscopy (SIMS). Cyclic voltammetry indicates that the transport of Li ions in the TiO2 thin film is diffusion limited. Chronoamperometry and its corresponding optical modulation measurements show that the increase of the quantity of inserted charge causes the appearance of two absorption bands, and a blueshift of the TiO2 film absorption edge. The observed optical changes were attributed to band gap broadening.