Comparison of Thin Films of Titanium Dioxide Deposited by Sputtering and Sol-Gel Methods for Waveguiding Applications

Abstract

In this work, TiO2 thin films were deposited onto glass substrate by two different techniques: sol-gel dip-coating (SG) and reactive DC magnetron sputtering (Sput). The prepared samples have been characterized by means of micro-Raman, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) measurements, scanning electron microscopy (SEM), UV-Visible spectrophotometry, and M-Lines spectroscopy (MLS). The micro-Raman results showed an amorphous TiO2-SG phase and the vibrational mode of TiO2-Sput is anatase phase. DSC-TGA analysis was used to investigate the thermal properties of the TiO2 material. SEM spectroscopy has shown that TiO2-SG has a disordered and more porous surface, TiO2-Sput sample is homogeneous and shows uniform distribution of densely packed well-defined grains. The obtained films have an optical transmittance varying from 60 to 88% in the visible region. The optical band gaps deduced from the transmittance are 3.48 and 3.53 eV for TiO2-SG and TiO2-Sput, respectively. The optical waveguiding measurements carried out on TiO2-SG and TiO2-Sput films show single guided modes behavior (TE0 and TM0). These measurements have allowed deducing the refractive index and thickness values that are 2.06 at 216 nm for TiO2-SG and 2.26 at 204 nm for TiO2-Sput thin films. The analysis of waveguiding properties indicates that amorphous TiO2 may prove to be more efficient in photonic device as compared to crystalline TiO2. Keywords: TiO2, thin films, sol-gel, sputtering, anatase, waveguiding.