Characterization of Birefringent Titanium-Oxide Thin Films Deposited by DC Sputtering
Keywords:Birefringence, DC Sputtering, Titania, Titanium Oxide, TiO2, Refractive Index
This work presents the characterization of birefringent properties of titanium-oxide thin films using spectrophotometry and double-cavity Fabry-Perot structures. All films were deposited by DC sputtering over tilted substrates and the birefringence was characterized as a function of the deposition angle by the numerical difference between the refractive indexes for s- and p-polarized light beams. As a result, the highest value of birefringence (0.03) was obtained for samples tilted at 21º (having the normal axis as reference). A polarizing narrow-band Fabry-Perot filter centered at 400 and 700nm was designed by means of numerical simulations of the multilayer structures using a MATLAB© toolbox to solve the classical optical equations. Using this designed double-cavity Fabry-Perot structure [Ag(40nm) / TiO2(160nm) / Ag(40nm) / TiO2(164nm) / Ag(40nm)], transmittance ratios (Tp/Ts) for p- and s-polarized light beams resulted 1.70 at a wavelength of 699nm and 1.36 at another wavelength of 393nm (centers of the two narrow-band peaks), which corroborated the birefringent characteristics of the nearly-stoichiometric titania (TiO2) thin films.