Physical and optical waveguiding properties of sol-gel deposited nano-structured TiO<SUB align="right">2 thin films: a study on the effect of synthesis parameters

Abstract

In this paper, amorphous and polycrystalline nano-structured TiO2 thin films were prepared by sol-gel dip-coating process. The effects of different fabrication parameters (e.g., withdrawal speed, annealing temperature) on the structural, morphological and optical properties of the synthesised films were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and UV-visible Spectrophotometry. Waveguiding properties such as propagating modes and optical loss were measured at 632.8 nm by M-lines spectroscopy (MLS). The results indicate that all thin films annealed at 500oC exhibit XRD patterns and FTIR data consistent with the TiO2 anatase phase. AFM images have revealed that morphology and surface roughness of deposited thin films depend on withdrawal speed and heat treatment temperature. The UV-visible transmittance results show that all thin films were transparent with an average transmittance higher than 70% in the visible region. The results have also demonstrated from MLS measurements that TiO2 thin film slab waveguides deposited at withdrawal speed of 2 cm/min and annealed at 500°C exhibit not only better light confinement but also lower optical loss than those dip-coated at the speed of 1 and 3 cm/min.