Structural properties of single and multilayer ITO and TiO2 films deposited by reactive pulsed laser ablation deposition technique

Indium tin oxide (ITO) and titanium dioxide (TiO2) single layer and double layer ITO/TiO2 films were prepared using reactive pulsed laser ablation deposition (RPLAD) with an ArF excimer laser. The films were deposited on SiO2 substrates heated at 200 and 400 °C. ITO and TiO2 films with uniform thicknesses of about 400 and 800 nm, respectively, over large areas were prepared. X-ray diffraction (XRD) analysis revealed that the ITO films are formed of highly orientated nanocrystals with an average particle size of 10-15 nm. Atomic force microscopy (AFM) observations indicate rough ITO films surfaces with average roughness of 26-30 nm. Pores were also observed. TiO2 films deposited on the prepared ITO films result less crystalline. Annealing at 300 and 500 °C for three consecutive hours promoted formation of TiO2 anatase phase, with crystal size of ∼6-7 nm. From the scanning transmission electron microscope (STEM) images, it can be seen that the TiO2 films deposited onto the prepared ITO films present a relatively high pore sizes with an average pore diameter of ∼40 nm and excellent uniformity. In addition, STEM cross-sectional analysis of our films showed a columnar structure but no evidence of voids in the structure. Therefore, films exhibited large surface area, well suited for dye-sensitized solar cells (DSSC) applications.