Abstract
Titanium oxide coatings have been deposited by the sol-gel dip-coating method. Crystallization of titanium oxide coatings was then achieved through thermal annealing at temperatures above 400 °C. The structural properties and surface morphology of the crystallized coatings were studied by micro-Raman spectroscopy and atomic force microscopy, respectively. Characterization technique, based on least-square fitting to the measured reflectance and transmittance spectra, is used to determine the refractive indices of the crystallized TiO2 coatings. The stability of the synthesized sol was also investigated by dynamic light scattering particle size analyzer. The influence of the thermal annealing on the optical properties was then discussed. The increase in refractive index with high temperature thermal annealing process was observed, obtaining refractive index values from 1.98 to 2.57 at He-Ne laser wavelength of 633 nm. The Raman spectroscopy and atomic force microscopy studies indicate that the index variation is due to the changes in crystalline phase, density, and morphology during thermal annealing.
Highlights
Titanium oxide (TiO2) coatings have been extensively studied and used owing to their great potential in optical device application, such as planar waveguides [1], antireflective coatings [2,3], and solar cells [4,5,6]
For sol-gel derived TiO2 coating, the high porosity combined with the existence of residual organic components make the optical constants of coating layer quite different from that of solid coating and bulk materials
In our previous work [26], the optical constants of amorphous TiO2 coatings were determined by spectroscopic ellipsometry, and these amorphous TiO2 coatings have been successfully used for fabrication of two-layer antireflective coatings [3]
Summary
Titanium oxide (TiO2) coatings have been extensively studied and used owing to their great potential in optical device application, such as planar waveguides [1], antireflective coatings [2,3], and solar cells [4,5,6]. For sol-gel derived TiO2 coating, the high porosity combined with the existence of residual organic components make the optical constants of coating layer quite different from that of solid coating and bulk materials. It is very important to determine the optical constants for sol-gel derived coatings systemically. The reports available for optical constants of crystallized sol-gel TiO2 coatings are scarce and not yet taken seriously. It is of interest to study the optical constants of the crystallized sol-gel TiO2 coatings. We performed this work to understand the optical properties of crystallized sol-gel TiO2 coatings more systemically and deeply. The crystalline structure, surface morphology, and optical properties of the TiO2 coatings were studied and discussed. We demonstrated that the increase in refractive index was due to combined effects of crystalline phase, density, and morphology during thermal annealing
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
