The effect of heat treatment on superhydrophilicity of TiO2 nano thin films
Superconductivity Research Laboratory(SRL), Department of Physics, University of Tehran, North Kargar Av., PO Box 14395-547, Tehran, Iran
Corresponding author: firstname.lastname@example.org
Accepted: 2 August 2007
Published online: 31 October 2007
TiO2 thin films were synthesized by the sol-gel method and spin coating process. The calcination temperature was changed from 100 to 550 °C. XRD patterns show increasing the content of polycrystalline anatase phase with increasing the calcination temperature. The AFM results indicate granular morphology of the films, which particle size changes from 22 to 166 nm by increasing the calcination temperature. The RBS, EDX and Raman spectroscopy of the films show the ratio of Ti:O ~0.5, and diffusion of sodium ions from substrate into the layer, by increasing the calcination temperature. The UV-vis spectroscopy of the films indicates a red shift by increasing the calcination temperature. The contact angle meter experiment shows that superhydrophilicity of the films depends on the formation of anatase crystal structure and diffused sodium content from substrate to the layer. The best hydrophilicity property was observed at 450 °C calcination temperature, where the film is converted to a superhydrophilic surface after 10 min under 2 mW/cm2 UV irradiation. Water droplet on TiO2 thin film on Si(111), Si(100), and quartz substrates is spread to smaller angles rather than glass and polycrystalline Si substrates under UV irradiation.
PACS: 68.08.Bc – Wetting / 73.21.Ac – Multilayers / 82.30.Rs – Hydrogen bonding, hydrophilic effects
© EDP Sciences, 2007