TiO 2 thin films were synthesized by sol-gel process: titanium tetraisopropoxide (TTIP) was dissolved in isopropanol, and then hydrolyzed by adding a water/isopropanol mixture with a controlled hydrolysis ratio. The as prepared sol was deposited by “dip-coating” on a glass substrate with a controlled withdrawal speed. The obtained films were annealed at 350 and 500 °C (2 h). The morphological properties of the prepared films were analyzed by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The optical waveguiding properties of TiO 2 films were investigated for both annealing temperature using m-lines spectroscopy. The refractive indices and the film thickness were determined from the measured effective indices. The results show that the synthesized planar waveguides are multimodes and demonstrate low propagation losses of 0.5 and 0.8 dB/cm for annealing temperature 350 and 500 °C, respectively.
References
[1]
Yamasaki, S.; Hata, N.; Yoshida, T.; Oheda, H.; Matsuda, A.; Okushi, H.; Tanaka, K. Annealing studies on low optical absorption of GD a-Si:H using photoacoustic spectroscopy. J. Phys. Colloq. 1981, 42, C4-297–C4-300.
[2]
Brudnik, A.; Czternastek, H.; Zakrzewska, K.; Jachimowski, M. Plasma-emission-controlled d.c. magnetron sputtering of TiO2？x thin films. Thin Solid Films 1991, 199, 45–58.
[3]
Garzella, C.; Comini, E.; Tempesti, E.; Frigeri, C.; Sberveglieri, G. TiO2 thin films by a novel sol-gel processing for gas sensor applications. Sens. Actuators B 2000, 68, 189–196, doi:10.1016/S0925-4005(00)00428-7.
[4]
San Vicente, G.; Morales, A.; Gutiérrez, M.T. Sol-gel TiO2 antireflective films for textured monocrystalline silicon solar cells. Thin Solid Films 2002, 403–404, 335–338.
[5]
Wongcharee, K.; Brungs, M.; Chaplin, R.; Hong, Y.J.; Pillar, R. Sol-gel processing by aging and pore creator addition for porous silica antireflective coatings. J. Sol-Gel Sci. Technol. 2002, 25, 215–221.
[6]
Yang, L.; Scott Saavedra, S.; Armstrong, N.R.; Hayes, J. Fabrication and characterization of low-loss, sol-gel planar waveguides. Anal. Chem. 1994, 66, 1254–1263, doi:10.1021/ac00080a010.
[7]
Znaidi, L.; Seraphimova, R.; Bocquet, J.F.; Colbeau-Justin, C.; Pommier, C. A semi-continuous process for the synthesis of nanosize TiO2 powders and their use as photocatalysts. Mat. Res. Bull. 2001, 36, 811–825, doi:10.1016/S0025-5408(00)00482-7.
[8]
Montagna, M.; Moser, E.; Visintainer, F.; Ferrari, M.; Zampedri, L.; Martucci, A.; Guglielmi, M.; Ivanda, M. Nucleation of titania nanocrystals in silica titania waveguides. J. Sol-Gel Sci. Technol. 2003, 26, 241–244.
[9]
Bernard, C.; Chaussedent, S.; Monteil, A.; Ferrari, M. Molecular dynamics simulation of an Er-activated silica-titania glass: Composition influence on the structural properties. Philos. Mag. B 2002, 82, 681–693.
[10]
Yanagida, S.; Senadeera, G.K.R.; Nakamura, K.; Kitamura, T.; Wada, Y. Polythiophene-sensitized TiO2 solar cells. J. Photochem. Photobiol. A 2004, 166, 75–80, doi:10.1016/j.jphotochem.2004.04.039.
[11]
Shen, J.; Yang, T.; Zhang, Q.; Wang, J. Nanoporous TiO2 coatings for infrared detectors. J. Sol-Gel Sci. Technol. 2003, 26, 1029–1032.
[12]
Wang, Z.; Helmersson, U.; K？ll, P.O. Optical properties of anatase TiO2 thin films prepared by aqueous sol-gel process at low temperature. Thin Solid Films 2002, 405, 50–54, doi:10.1016/S0040-6090(01)01767-9.
[13]
Pandiyan, R.; Micheli, V.; Ristic, D.; Bartali, R.; Pepponi, G.; Barozzi, M.; Gottardi, G.; Ferrari, M.; Laidani, N. Structural and near-infra red luminescence properties of Nd-doped TiO2 films deposited by RF sputtering. J. Mater. Chem. 2012, 22, 22424–22432, doi:10.1039/c2jm34708c.
[14]
Conde-Gallardo, A.; García-Rocha, M.; Palomino-Merino, R.; Velásquez-Quesada, M.P.; Hernández-Calderón, I. Photoluminescence properties of Tb3+ and Eu3+ ions hosted in TiO2 matrix. Appl. Surf. Sci. 2003, 212–213, 583–588.
[15]
Wang, X.; Fujimaki, M.; Awazu, K. Photonic crystal structures in titanium dioxide (TiO2) and their optimal design. Opt. Express 2005, 13, 1486–1497, doi:10.1364/OPEX.13.001486.
[16]
Uhlmann, D.R.; Teowee, G. Sol-gel science and technology: Current state and future prospects. J. Sol-Gel Sci. Technol. 1998, 13, 153–162.
Znaidi, L. Sol-gel-deposited ZnO thin films: A review. Mater. Sci. Eng. B 2010, 174, 18–30, doi:10.1016/j.mseb.2010.07.001.
[19]
Nishide, T.; Sato, M.; Hara, H. Crystal structure and optical property of TiO2 gels and films prepared from Ti-edta complexes as titania precursors. J. Mater. Sci. 2000, 35, 465–469, doi:10.1023/A:1004731804075.
[20]
Oh, S.H.; Kim, D.J.; Hahn, S.H.; Kim, E.J. Comparison of optical and photocatalytic properties of TiO2 thin films prepared by electron-beam evaporation and sol-gel dip-coating. Mater. Lett. 2003, 57, 4151–4155, doi:10.1016/S0167-577X(03)00281-7.
[21]
Znaidi, L.; Bocquet, J.F.; Pommier, C. Elaboration of TiO2 nanometric powders and thin films aerogels. AIDIC conf. Ser. 2000, 4, 109–114.
[22]
Znaidi, L.; Touam, T.; Vrel, D.; Kuznetsova, I.N.; Fischer, A.; Boudrioua, A. Waveguiding properties of nanostructured TiO2 thin films synthesized by sol-gel process. AIP Conf. Proc. 2011, 1400, 268–273.
[23]
Ulrich, R. Theory of the prism-film coupler by plane-wave analysis. J. Opt. Soc. Am. 1970, 60, 1337–1350, doi:10.1364/JOSA.60.001337.
[24]
Mechiakh, R.; Ben Sedrine, N.; Ben Naceur, J.; Chtourou, R. Elaboration and characterization of nanocrystalline TiO2 thin films prepared by sol-gel dip-coating. Surf. Coat. Technol. 2011, 206, 243–249, doi:10.1016/j.surfcoat.2011.06.053.
[25]
Urlacher, C.; Dumas, J.; Serughetti, J.; Mugnier, J.; Munoz, M. Planar ZrO2 waveguides prepared by the sol-gel process: Structural and optical properties. J. Sol-Gel Sci. Technol. 1997, 8, 999–1005.
[26]
Tien, P.K.; Ulrich, R. Theory of prism-film coupler and thin-film light guides. J. Opt. Soc. Am. 1970, 60, 1325–1337, doi:10.1364/JOSA.60.001325.
[27]
Kersten, R.Th. Numerical solution of the mode-equation of planar dielectric waveguides to determine their refractive index and thickness by means of a prism-film coupler. Opt. Commun. 1973, 9, 427–431, doi:10.1016/0030-4018(73)90288-5.
[28]
Wang, B.; Hu, L. Optical and surface properties of hybrid TiO2/ormosil planar waveguide prepared by the sol-gel process. Ceram. Int. 2006, 32, 7–12, doi:10.1016/j.ceramint.2004.11.013.
[29]
Strohkendl, F.P.; Fluck, D.; Günter, P.; Irmscher, R.; Buchal, Ch. Nonleaky optical waveguides in KNbO3 by ultralow dose MeV He ion implantation. Appl. Phys. Lett. 1991, 59, 3354–3356, doi:10.1063/1.105724.
[30]
Weber, H.P.; Dunn, F.A.; Leibolt, W.N. Loss measurements in thin-film optical waveguides. Appl. Opt. 1973, 12, 755–757, doi:10.1364/AO.12.000755.
[31]
Boudrioua, A.; Loulergue, J.C. New approach for loss measurements in optical planar waveguides. Opt. Commun. 1997, 137, 37–40, doi:10.1016/S0030-4018(96)00764-X.
[32]
Ehrhart, G.; Capoen, B.; Robbe, O.; Boy, Ph.; Turrell, S.; Bouazaoui, M. Structural and optical properties of n-propoxide sol-gel derived ZrO2 thin films. Thin Solid Films 2006, 496, 227–233, doi:10.1016/j.tsf.2005.08.309.
[33]
Bahtat, M.; Mugnier, J.; Lou, L.; Serughetti, J. Planar TiO2 waveguides by the sol-gel process: The relationship of structure to properties. SPIEProc. 1992, 1758, 173.
