High Refractive Index Silica-Titania Films Fabricated via the Sol-Gel Method and Dip-Coating Technique-Physical and Chemical Characterization

Magdalena Zięba; Katarzyna Wojtasik; Cuma Tyszkiewicz; Ewa Gondek; Jacek Nizioł; Katarzyna Suchanek; Michał Wojtasik; Wojciech Pakieła; Paweł Karasiński

doi:10.3390/ma14237125

High Refractive Index Silica-Titania Films Fabricated via the Sol-Gel Method and Dip-Coating Technique-Physical and Chemical Characterization

Materials (Basel). 2021 Nov 23;14(23):7125. doi: 10.3390/ma14237125.

Authors

Magdalena Zięba¹, Katarzyna Wojtasik^{1

2}, Cuma Tyszkiewicz¹, Ewa Gondek², Jacek Nizioł³, Katarzyna Suchanek², Michał Wojtasik⁴, Wojciech Pakieła⁵, Paweł Karasiński¹

Affiliations

¹ Department of Optoelectronics, Silesian University of Technology, B. Krzywoustego 2, 44-100 Gliwice, Poland.
² Department of Physics, Cracow University of Technology, Podchorążych 1, 30-084 Kraków, Poland.
³ Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland.
⁴ Oil and Gas Institute-National Research Institute, Lubicz 25A, 31-503 Krakow, Poland.
⁵ Faculty of Mechanical Engineering, Institute of Engineering Materials and Biomaterials, Silesian University of Technology, ul. Konarskiego 18a, 44-100 Gliwice, Poland.

Abstract

Crack-free binary SiO_x:TiO_y composite films with the refractive index of ~1.94 at wavelength 632.8 nm were fabricated on soda-lime glass substrates, using the sol-gel method and dip-coating technique. With the use of transmission spectrophotometry and Tauc method, the energy of the optical band gap of 3.6 eV and 4.0 eV were determined for indirect and direct optical allowed transitions, respectively. Using the reflectance spectrophotometry method, optical homogeneity of SiO_x:TiO_y composite films was confirmed. The complex refractive index determined by spectroscopic ellipsometry confirmed good transmission properties of the developed SiO_x:TiO_y films in the Vis-NIR spectral range. The surface morphology of the SiO_x:TiO_y films by atomic force microscopy (AFM) and scanning electron microscopy (SEM) methods demonstrated their high smoothness, with the root mean square roughness at the level of ~0.15 nm. Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy were used to investigate the chemical properties of the SiO_x:TiO_y material. The developed binary composite films SiO_x:TiO_y demonstrate good waveguide properties, for which optical losses of 1.1 dB/cm and 2.7 dB/cm were determined, for fundamental TM₀ and TE₀ modes, respectively.

Keywords: dip-coating technique; optical band gap; optical losses; optical waveguide film; planar waveguide; silica–titania films; sol–gel.

Abstract

Grants and funding