Study of nitrogen ion doping of titanium dioxide films (original) (raw)
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Characterization of nitrogen-implanted TiO2 nanostructured films
Materials Science and Engineering: B, 2006
Nanostructured tanium dioxide (TiO 2 ) films were implanted with N + at 40 keV and ion dose range of 10 16 /cm 2 to 4 × 10 16 /cm 2 , and annealed at temperatures between 673 and 973 K. From XRD and TEM analyses it was found that the anatase phase of TiO 2 remained stable up to annealing temperature of 973 K. The samples showed narrower XRD peaks corresponding to larger mean-grain sizes comparing to the un-implanted TiO 2 samples. The SIMS depth profile showed a peak of nitrogen concentration at about 60 nm beneath the film surface and this was confirmed using the SRIM-2003 program for simulating ion beam interactions with matter. The absorption spectra of the films as measured using spectrophotometer were found to shift toward longer wavelengths with the increase of ion dose.
Investigation on the nitrogen doping of multilayered, porous TiO2 thin films
Thin Solid Films, 2008
N-doping is often used to improve the photocatalytic properties of TiO 2 films in order to achieve visible light response. In this work, we study the effect of annealing treatment (temperature and atmosphere) on the structural and optical properties of undoped and N-doped TiO 2 films by means of X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Rutherford backscattering (RBS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE) and UV-VIS optical transmission spectroscopy. Porous five-layer TiO 2 films were deposited by sol-gel method on quartz substrate and thermally treated in oxygen or NH 3 flow at 500 and 600°C. Significant doping effect was achieved after annealing at 600°C in NH 3 and a shift in optical bandgap value down to visible range (2.69 eV) was observed.
Characterization of Transparent and Conducting Doped Titanium Dioxide for Energy Conversion
2015
Niobium-Doped Titanium Dioxide thin films were prepared by RF magnetron sputtering at room temperature. The TiO2 thin films were deposited with thicknesses of about 400 nm, doped with different concentration of niobium and then annealed in H2 environment at 460 o C. The influence of doping and post deposition annealing in H2 environment on the structural and composition was studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The structure and composition of the prepared films were found to be affected by the Nb dopant concentration and the post deposition annealing. This study found that doping TiO2 with Nb implying improved conductivity compared to pure TiO2 which exhibits insulating properties. TiO2/p-CdTe photovoltaic devices with efficiency of about 2 % were fabricated.
Electrochemical Properties of Transparent Conducting Films of Tantalum-Doped Titanium Dioxide
Electrochimica Acta, 2017
Highly conducting, optically transparent Ta-doped TiO2 (anatase) thin films are grown on ordinary soda-lime glass substrate by pulsed-laser deposition. They exhibit quasi-reversible cyclic voltammograms of Fe(CN)6 3-/4and dimethylviologen redox couples, mimicking the electrochemical activity of F-doped SnO2 (FTO). Hence, our Ta-doped titania films can prospectively replace FTO, e.g. in homo-junction dye-sensitized and perovskite solar cells. However, these films are idle for the Ru(bpy)3 2+ oxidation, which is attributed to the spacecharge barrier. The flatband potential of our Ta-doped TiO2 is comparable to that of undoped reference film and/or the pristine anatase single-crystal electrode. Our films show photoelectrochemical activity upon irradiation with UV light at potentials positive to flatband. The photocurrents decrease proportionally to the increase of Ta-content. The Li-insertion ability analogously decreases with the increasing Ta-content. This is attributed to the positive charge of Ta 5+ cations which occupy the Ti 4+ sites in anatase lattice and thus impede the Li +-transport. Consistent with the quasi-metallic nature of our films, the Li-extraction peak in cyclic voltammograms shows no cut at larger potentials.
STRUCTURAL PROPERTIES OF NITROGEN DOPED ANATASE AND RUTILE TiO2 THIN FILMS
JOURNAL OF ADVANCES IN PHYSICS, 2015
Anatase and rutile TiO2 thin films have been doped by N ion implantation. The effect of N doping on the structural changes of TiO2 thin films and its correlation to the optical and chemical properties of the films is investigated. The depth and concentration of the implanted N atoms is found not to exhibit substantial difference for anatase and rutile phases. The energy loss of the implanted N atoms correlates well to the energy gained by O and Ti atoms in the TiO2 lattice. An increased number of O vacancies are found to be generated as compared to Ti for both anatase and rutile phases. The energy loss mechanisms of the implanted N atoms together with the O vacancy generation are found to be the major driving forces for facilitating enhanced optical and chemical properties of the TiO2 thin films.Â
X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) provide a unique opportunity to probe both the highest occupied and the lowest unoccupied states in matter with bulk sensitivity. In this work, a combination of valence-to-core XES and pre-edge XAS techniques are used to determine changes induced in the electronic structure of titanium dioxide doped with nitrogen atoms. Based on the experimental data it is shown that N-doping leads to incorporation of the p-states on the occupied electronic site. For the conduction band, a decrease in population of the lowest unoccupied d-localized orbitals with respect to the d-delocalized orbitals is observed. As confirmed by theoretical calculations, the N p-states in TiO 2 structure are characterized by higher binding energy than the O p-states which gives a smaller value of the band-gap energy for the doped material.
The Journal of Physical Chemistry C, 2014
For a systematic study of the material, samples of W/N-codoped titania with different concentrations of the dopants were prepared. The physicochemical properties and in particular their band structure were subsequently evaluated experimentally to elucidate the effect of W-doping, N-doping, and W/N-codoping on the band structure of TiO 2. For this purpose, a combined approach of optical spectroscopy and electrochemical impedance spectroscopy was chosen. The doped samples featured both a reduced band gap and a positively shifted conduction band edge. Both conduction band edge and band gap followed a linear dependence on the nitrogen content. They also demonstrate visible light absorption capability, which is associated with interstitial nitrogen doping. Tungsten doping did not influence the band structure of TiO 2 directly. It did, however, facilitate nitrogen uptake and stabilize it at higher temperatures. These higher nitrogen doping levels then in turn reduced the band gap and lowered the conduction band edge. Codoping with tungsten therefore offers an excellent way to precisely adjust the nitrogen content and correspondingly the conduction band position of titanium dioxide.
Chemical Vapor Deposition, 2013
N-doped titanium dioxide (TiO 2 ) thin films are grown on Si(100) and indium tin oxide (ITO)-coated borosilicate glass substrates by metal-organic (MO)CVD. The intrinsic doping of TiO 2 thin films is achieved using all-nitrogen-coordinated Ti precursors in the presence of oxygen. The titanium amide-guanidinate complex, [Ti(NMe 2 ) 3 (guan)] (guan ¼ N,N 0 -diisopropyl-2-dimethylamidoguanidinato) has been developed to compensate for the thermal instability of the parent alkylamide [Ti(NMe 2 ) 4 ]. Both of these amide-based compounds are tested and compared as precursors for intrinsically N-doped TiO 2 at various deposition temperatures in the absence of additional N sources. The structure and morphology of TiO 2 thin films are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Rutherford back scattering (RBS), nuclear reaction analysis (NRA), and secondary ion mass spectrometry (SIMS) analyses are performed to determine N content and distribution in the films. The optical and photoelectrochemical properties of TiO 2 thin films on ITO substrates are also examined. N-doped TiO 2 thin films, grown from [Ti(NMe 2 ) 3 (guan)] at 600 8C, exhibit the lowest optical absorption edge (3.0 eV) and the highest visible light photocurrent response. When compared to undoped TiO 2 , while in UV light photoconversion efficiency decreases significantly, the intrinsically N-doped TiO 2 shows enhanced photocurrents under visible light irradiation.
TiO2 Doped with Nitrogen: Synthesis and Characterization
Journal of Nanoscience and Nanotechnology, 2008
In this study, nitrogen-doped titanium dioxide (TiO2) powders were synthesized in two ways: by heating of titanium hydroxide with urea and by direct hydrolysis of titanium tetraisopropoxide (TTIP) with ammonium hydroxide. The samples were characterized by structural (XRD), analytical (XPS), optical (UV/Vis absorption/reflection and Raman spectroscopy) and morphological (SEM, TEM) techniques. The characterization suggested that the doped materials have anatase crystalline form without any detectable peaks that correspond to dopants. The absorption threshold of titanium dioxide was moved in the visible range of optical spectrum from 3.2 eV to 2.20 eV. Particle sizes of synthesized powders were obtained from XRD measurements and from TEM data ranging from 6–20 nm. XPS and Raman spectroscopy were used for detection of nitrogen in doped samples.