We investigate the effect of TiCl 4 treatment on the refractive index of a nanoporous TiO 2 film. A nanoparticulate TiO 2 film prepared on a glass substrate was immersed in a TiCl 4 aqueous solution. The subsequent reaction of TiCl 4 with H 2 O produces TiO 2 and thus modifies the density and the refractive index of the film. With increasing TiCl 4 concentration, the refractive index initially increased and then declined after being maximized (n = 2.02 at 633 nm) at 0.08 M concentration. A refractive index change as large as 0.45 could be obtained with the TiCl 4 treatment, making it possible to achieve diffraction efficiency exceeding 80% in a diffraction grating-embedded TiO 2 film. For high TiCl 4 concentrations of 0.32 M and 0.64 M, the refractive index remained nearly unchanged. This was attributed to the limited permeability of high-viscosity TiCl 4 solutions into the nanoporous films. The measured pore size distributions were in good agreement with the results of a diffraction analysis and refractive index measurement.
Bibliographical noteFunding Information:
This work was supported by the Basic Science Research Program through the National Research Foundation (NRF) funded by the Ministry of Education, Science and Technology of Korea ( NRF 2012R1A1A2044557 ).
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Physics and Astronomy(all)
- Surfaces and Interfaces
- Surfaces, Coatings and Films