title: Microstructure and optical dispersion characterization of nanocomposite sol-gel TiO₂-SiO₂ thin films with different compositions.
abstract: Nanocomposite TiO2-SiO2 thin films with different compositions (from 0 to 100 mol% TiO2) were deposited by sol-gel dip-coating method on silicon substrate. Crystal structure, chemical bonding configuration, composition and morphology evolutions with composition were followed by Raman scattering, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy respectively. The refractive index and the extinction coefficient were derived in a broad band wavelength (250-900 nm) from spectroscopic ellipsometry data with high accuracy and correlated with composition and microstructure. Results showed an anatase structure for 100% TiO2 with a grain size in 6-10nm range. Whereas, the inclusion of SiO2 enlarges the optical band gap and suppresses the grain growth up to 4 nm in size. High TiO2 dispersion in SiO2 matrix was observed for all mixed materials. The refractive index (at λ=600 nm) increases linearly with composition from 1.48 (in 100% SiO2) to 2.22 (in 100% TiO2) leading to lower dense material, its dispersion being discussed in terms of the Wemple-DiDomenico single oscillator model. Hence, the optical parameters, such optical dispersion energies E0 and Ed, the average oscillators, strength S0 and wavelength λ0 and the ratio of the carrier concentration to the effective mass N/m(∗) have been derived. The analysis revealed a strong dependence on composition and structure. The optical response was also investigated in term of complex optical conductivity (σ) and both volume and surface energy loss functions (VELF and SELF).
authors.affiliation: CRTSE- Division DDCS 02, Bd Dr Frantz Fanon BP: 140, les 07 merveilles, 16038 Algiers, Algeria. Electronic address: kermadisalim@yahoo.fr.
authors.forename: S
authors.initials: S
authors.lastname: Kermadi
authors.affiliation: Department of Chemistry, Laboratory of Physico-Chemistry of Materials and Environment USTHB University, BO Box 32 El Alia, 16111 Algiers, Algeria.
authors.forename: N
authors.initials: N
authors.lastname: Agoudjil
authors.affiliation: CRTSE- Division DDCS 02, Bd Dr Frantz Fanon BP: 140, les 07 merveilles, 16038 Algiers, Algeria.
authors.forename: S
authors.initials: S
authors.lastname: Sali
authors.affiliation: CRTSE- Division DDCS 02, Bd Dr Frantz Fanon BP: 140, les 07 merveilles, 16038 Algiers, Algeria.
authors.forename: L
authors.initials: L
authors.lastname: Zougar
authors.affiliation: CRTSE- Division DDCS 02, Bd Dr Frantz Fanon BP: 140, les 07 merveilles, 16038 Algiers, Algeria.
authors.forename: M
authors.initials: M
authors.lastname: Boumaour
authors.affiliation: Laboratoire de Chimie Physique-Approche Multi-échelle des milieux complexes (LCP-A2MC, EA4632), Université de Lorraine, 1 Boulevard Dominique François Arago, 57070 METZ Technopôle, France.
authors.forename: L
authors.initials: L
authors.lastname: Broch
authors.affiliation: Laboratoire de Chimie Physique-Approche Multi-échelle des milieux complexes (LCP-A2MC, EA4632), Université de Lorraine, 1 Boulevard Dominique François Arago, 57070 METZ Technopôle, France.
authors.forename: A
authors.initials: A
authors.lastname: En Naciri
authors.affiliation: Thin Film Centre, University of the West of Scotland, Paisley, PA1 2BE, SUPA (Scottish Universities Physics Alliance), Scotland, United Kingdom.
authors.forename: F
authors.initials: F
authors.lastname: Placido
mesh_terms: D004560:Electricity; D008958:Models, Molecular; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D055620:Optical Phenomena; D044367:Phase Transition; D017785:Photons; D012031:Refractometry; D012822:Silicon Dioxide / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry*
chemical_list: C507641:TiO2-SiO2; D012822:Silicon Dioxide; D014025:Titanium
keywords: Dispersion parameters; Energy loss; Nanocomposite thin films; Optical conductivity; Sol–gel