Physical properties of the CNT:TiO2 thin films prepared by sol–gel dip coating

Abstract

Uniform and highly adherent thin films of CNT:TiO2 were synthesized by sol–gel dip coating method. Both TiO2 and CNT:TiO2 films showed very identical structural characteristics and no significant changes in the lattice values were observed. The crystalline size decreased from 20nm for TiO2 film to 17nm for the 4%CNT:TiO2 film. The film surface was very smooth and compact, as indicated by the roughness data obtained from AFM measurements; the root mean square (rms) average of the roughness was as low as 3nm. The HRTEM showed that the CNTs are embedded in the matrix of TiO2 indicating the formation of a composite. In Raman spectra the characteristic vibrations of the TiO2 are identified, the increase in the FWHM of main anatase peak (144cm−1) in the case of the 4%CNT:TiO2 film is interpreted as due to the incorporation of CNTs in the film. At the wavelength of 600nm the refractive index of pure TiO2 was 2.07 and the 4%CNT:TiO2 showed a value of 2.29. The photoresponse curves showed typical features of charge trapping centers in the band gap of the films.