Compositional Tailored Sol-Gel SiO₂–TiO₂ Thin Films: Crystallization, Chemical Bonding Configuration, and Optical Properties

Abstract

Thin films of SiO 2 -TiO 2 composite oxides with various SiO 2 :TiO 2 compositions were prepared by the sol-gel method, using tetraethylorthosilicate (TEOS) and titanium tetraisopropoxide (TTIP) as precursors. The composition, crystal structure, and chemical bonding configuration of the as-deposited and annealed SiO 2 -TiO 2 thin films were analyzed using Rutherford backscattering spectrometry (RBS), glancing incident angle x-ray diffraction (GIAXRD) and Fourier transform infrared spectroscopy (FTIR), respectively. Optical properties of the films were characterized by spectroscopic ellipsometry and ultraviolet-visible spectrophotometry. The Si/Ti ratios in the SiO 2 -TiO 2 films agree with the TEOS/TTIP molar ratio in the sol-gel precursor. When the TEOS/(TEOS + TTIP) ratio is greater than 40%, the SiO 2 -TiO 2 thin films remain amorphous (without formation of TiO 2 crystalline phase) after annealing at temperatures as high as 700°C. FTIR spectra indicate that the quantity of Si-O-Ti bonding can be maximized when the TEOS:TTIP in the precursor is 80%:20%. The refractive index of the SiO 2 -TiO 2 films increases approximately linearly to the mixing ratio of TTIP/(TEOS + TTIP). However, SiO 2 -rich films possess higher ultraviolet-visible transmittance than the TiO 2 -rich films. The modification of microstructure and chemical bonding configuration in the SiO 2 -TiO 2 films by the composition and its influence on the optical properties are discussed.

Ultra-low-threshold Er:Yb sol-gel microlaser on silicon

“…The synthesis of the sol-gel for microlaser fabrication is based upon research in the Chen and Vahala groups [26,33]. However, to minimize cracking and enable high quality sol-gel silica, this previous sol-gel synthesis protocol was modified.…”

Open air plasma deposited antimicrobial SiOx/TiOx composite films for biomedical applications

“…Sol-Gel process [6][7][8] and plasmaenhanced chemical vapour deposition (PE-CVD) [9]. The Sol-Gel process is a wet chemical process and the PE-CVD is commonly performed under vacuum.…”

Low threshold Er3+/Yb3+co-doped microcavity laser

“…Figure 1 shows a series of thin films at different annealing temperatures. The related Si-O-Si absorption bands, which are near 450 cm -1 , 800 cm -1 and 1100 cm -1 , are clearly shown in figure 1 [33,34]. The corresponding Si-O-Si absorption bands become stronger at higher annealing temperature.…”

“…To synthesize the sol-gel silica thin film for microlaser fabrication, we refer to research in the Chen and Vahala groups [26,32]. However, this previous sol-gel synthesis protocol was modified to minimize cracking and enable high quality sol-gel silica.…”