Deposition of TiO2 Multilayer Thin Films Doped with Cobalt and Studying the Effect of Annealing Temperatures and Number of Layers on the Structural and Morphological of Thin Films

The effect of the number of layers and annealing temperatures on the structural and morphological properties of Co-doped TiO2 thin films which were fabricated by solgel spin-coating method was explored. The spin-coating process was repeated up to 4 times to gain 1- to 4-layer films. The 2-coated layer films were annealed at 523K and 723K for 60min. The XRD analysis showed the amorphous structures for as-deposited multilayer films, which could be suggested that cobalt ions do not lead to the formation of crystalline phase of TiO2 films without annealing process. Anatase phase of TiO2 with tetragonal crystal structure was observed for films annealed at 723K. The FESEM results indicated spherical nanoparticles which were risen in density with increasing the number of layers and grew when the annealing temperature was enhanced. RMS roughness was calculated by AFM analysis. It was found that RMS roughness of the films was increased by increasing the number of coating layers and annealing temperatures. The increase in roughness is desirable for solar cell applications.