Optical characterization of PLD grown nitrogen-doped TiO2 thin films (original) (raw)
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Applied Surface Science, 2017
N-doped TiO 2 thin films were prepared using pulsed laser deposition by ablating metallic Ti target with pulses of 248 nm wavelength, at 330 ºC substrate temperature in reactive atmospheres of N 2 /O 2 gas mixtures. These films were characterized by spectroscopic ellipsometry, X-ray photoelectron spectroscopy and X-ray diffraction. Optical properties are presented as a function of the N 2 content in the processing gas mixture and correlated to nitrogen incorporation into the deposited layers. In case of extinction coefficient, refractive index and optical band gap values a monotonically increasing tendency, a maximum and a linearly decreasing slope can be observed with increasing N concentration, respectively. It is also shown that the amount of substitutional N can be increased up to 7.7 at.%, but the high dopant concentration inhibits the crystallization of the samples. No peaks of crystalline titanium-nitride were detected despite the large amount of substitutionally incorporated nitrogen.
Optical and morphological properties of N-doped TiO2 thin films
Surface Science, 2011
Nitrogen doped titanium dioxide (TiO 2 ) thin films were deposited by RF magnetron sputtering onto various substrates. The films were prepared in plasma of argon, oxygen, and nitrogen, with varying the nitrogen content, from 0% up to 70%. The resulting TiOx-Ny films were found to consist of cubic TiN osbornite and tetragonal TiO 2 rutile phases. Using optical spectroscopy with large spectral range from 350 to 1000 nm, the band gap width was determined and a narrowing of the optical gap from 2.76 to 2.32 eV was observed as a function of the N-content. It was found that the optical properties of the TiOx-Ny layers are influenced by the surface morphology, roughness, surface energy and phase content. The chemical composition, the crystalline structure, the surface morphology and the surface energy were thoroughly studied by the Rutherford backscattering spectrometry (RBS), grazing-angle XRD, atomic force microscopy (AFM) and contact angle measurements (wettability), respectively.
Surface and Coatings Technology, 2014
TiO 2 absorbs mostly the UV part of the solar spectrum, which results in low efficiency of absorption for visible light applications. Using pulsed laser deposition technique, we introduce defect states in the band gap of TiO 2 by co-doping with N and C under different oxygen pressures (4, 50 and 100 mTorr) to tune the band gap towards visible region. This process yields anatase-rutile mixed phase films. As control samples, we deposit undoped TiO 2 films with the above mentioned oxygen pressures. Several characterization techniques are used to examine thin film properties such as X-ray diffraction for crystal structure, Raman spectroscopy for phase analysis, X-ray photoelectron spectroscopy for electronic structure, scanning electron microscopy for planar and columnar morphology and ultraviolet-visible diffuse reflectance spectroscopy for photo absorption. While undoped TiO 2 samples show only anatase phase, N and C co-doped TiO 2 samples exhibit transition from rutile to anatase with increasing oxygen pressure. Oxygen pressure also affects the surface morphology and columnar structure of the films such that columnar structure is favored under oxygen-rich conditions. Finally, visible absorption around 550 nm was obtained.
International journal of energy engineering, 2012
Undoped and nitrogen-doped titanium dioxide (TiO2) thin films of 400 nm thick deposited by spray pyrolysis were structurally and optically characterized. The effect of substrate temperature on the optical properties of the films was also investigated. Structural studies of the films were undertaken by X-ray diffraction (XRD). Energy dispersive X-ray (EDX) spectrum analysis was used to confirm the presence of nitrogen atoms in the film after doping. The optical properties such as refractive index (n), energy band gap (Eg) and Urbach energy (Eu) were determined from spectrophotometric measurements of reflectance and transmittance for both undoped and doped films. The Undoped films had an energy band gap of 3.25 eV while the doped films had band gap of 2.90 eV. The Urbach energy increased from 1.00 eV for undoped films to 1.04 eV for the nitrogen-doped films. The reduction in energy band gap and increase in Urbach energy was attributed to the introduction of nitrogen impurity tail states on either the conduction band or the valence band of the titanium dioxide.
Optical and morphological properties of N-doped TiO< sub> 2 thin films
2011
N-doped TiO 2 thin films Band gap width Optical transmittance Wettability Titanium oxynitride Reactive gas sputtering Nitrogen doped titanium dioxide (TiO 2) thin films were deposited by RF magnetron sputtering onto various substrates. The films were prepared in plasma of argon, oxygen, and nitrogen, with varying the nitrogen content, from 0% up to 70%. The resulting TiOx-Ny films were found to consist of cubic TiN osbornite and tetragonal TiO 2 rutile phases. Using optical spectroscopy with large spectral range from 350 to 1000 nm, the band gap width was determined and a narrowing of the optical gap from 2.76 to 2.32 eV was observed as a function of the N-content. It was found that the optical properties of the TiOx-Ny layers are influenced by the surface morphology, roughness, surface energy and phase content. The chemical composition, the crystalline structure, the surface morphology and the surface energy were thoroughly studied by the Rutherford backscattering spectrometry (RBS), grazing-angle XRD, atomic force microscopy (AFM) and contact angle measurements (wettability), respectively.
Catalysis Communications, 2008
N-doped TiO 2 thin films were prepared by the laser ablation method under an N 2 gas atmosphere. Properties of the films such as color, the relative amount of N doped and the crystal structure strongly depended on substrate temperature and N 2 gas pressure. XPS data indicated that the amount of doped N unexpectedly increases with decreasing N 2 gas pressure in the range of ca. 40-270 Pa. We proposed that the N-doping occurred when N species and TiO 2 particles collide on the substrate. The decomposition of methylene blue using the N-doped TiO 2 thin film was also performed under visible light irradiation.
Coatings
Nitrogen-doped TiO2 films exhibit good photocatalytic ability in the visible (VIS) light region. This study reports the fabrication of these films using arc ion plating (AIP) in different ratios of nitrogen partial pressure (PN2) to oxygen partial pressure (PO2) without substrate heating and/or applied bias. This approach allows a significant broadening of the range of possible substrates to be used. X-ray diffraction (XRD) patterns indicate that these films deposited at room temperature are amorphous, and surface electron microscope (SEM) and atomic force microscope (AFM) images show that they have rough surfaces. Their transmittance and optical properties are measured with a spectrometer and ellipsometer, respectively. In addition, the bandgap energies of these amorphous films are derived by the ellipsometer from the Tauc–Lorentz (TL) model. The results indicate that the N-doped TiO2 film with a PN2/PO2 ratio of 1/4 attains the narrowest bandgap and the highest absorbance in the v...
Opt and morph prop of N-doped TiO2 thin films
Nitrogen doped titanium dioxide (TiO 2 ) thin films were deposited by RF magnetron sputtering onto various substrates. The films were prepared in plasma of argon, oxygen, and nitrogen, with varying the nitrogen content, from 0% up to 70%. The resulting TiOx-Ny films were found to consist of cubic TiN osbornite and tetragonal TiO 2 rutile phases. Using optical spectroscopy with large spectral range from 350 to 1000 nm, the band gap width was determined and a narrowing of the optical gap from 2.76 to 2.32 eV was observed as a function of the N-content. It was found that the optical properties of the TiOx-Ny layers are influenced by the surface morphology, roughness, surface energy and phase content. The chemical composition, the crystalline structure, the surface morphology and the surface energy were thoroughly studied by the Rutherford backscattering spectrometry (RBS), grazing-angle XRD, atomic force microscopy (AFM) and contact angle measurements (wettability), respectively.