This letter reports on the magnetic properties of Ti1-xCoxO2 anatase phase nanopowders with different Co contents. It is shown that oxygen vacancies play a fundamental role in promoting the long-range ferromagnetic order in the material studied, in addition to the transition-metal doping. Furthermore, the results allow ruling out the premise of a strict connection between Co clustering and the ferromagnetism observed in the Co:TiO2 anatase system.
The efforts in the optimization of the physical and chemical properties related to the photocatalytic efficiency of TiO2 nanoparticles relies mainly on defect engineering strategies, been the structural and the doping the most common ones. The doping of the anatase TiO2 structure with lanthanides elements potentially can turns the TiO2 optical absorption into the visible range increasing drastically its photocatalytic efficiency. Here we show that the processing of TiO2 nanoparticles in oxygen atmosphere and the La doping stabilizes the anatase phase. The La incorporation takes place mainly in…
In this work, we demonstrate that a well-established and facile ball milling approach using mixtures of commercial anatase nanoparticles and TiH2 introduces noble-metal-free photocatalytic H2 activity to titania. We characterize this synergistic effect in view of the nature of defects, state of hydroxylation, and investigate the effect on the energetics and kinetics of electronic states and the resulting H2 evolution performance.
Oxide based diluted magnetic semiconductor (DMS) materials have been a subject of increasing interest due to reports of room temperature ferromagnetism in several systems and their potential use in the development of spintronic devices. However, concerns on the stability of the magnetic properties of different DMS systems have been raised. Their magnetic moment is often unstable, vanishing with a characteristic decay time of weeks or months, which precludes the development of real applications. This paper reports on the ferromagnetic properties of two-year-aged Ti1-xCoxO2-δ reduced anatase nan…
In the present work, a simple strategy is used to thermally oxidize TiN nanopowder (ca. 20 nm) to an anatase phase of a TiO2:Ti3+:N compound. In contrast to the rutile phase of such a compound this photocatalyst provides photocatalytic activity for hydrogen evolution under AM1.5 conditions - this without the use of any noble metal co-catalyst. Moreover the photocatalyst is active and stable over extended periods of time (tested for 4 months). Importantly, to achieve successful conversion to the active anatase polymorph, sufficiently small starting particles of TiN are needed. The key factor fo…
An accurate experimental determination of electronic structure in semi-conductors nanopowders is a challenging task. We propose here to combine UPS and UV-Vis spectroscopies in order to get the full description of electronic bands alignment of powder samples, TiO2 rutile and anatase. For UPS measurements, two preparation methods, namely dropping method and electrophoretic deposition, were used to prepare layers of titania powders on a conducting substrate, ITO or Ag. Both methods lead to comparable results, with a quantitative description of the energy levels from the valence band. Combining t…
We have explored the effects of the Li intercalation on the electronic and magnetic properties of transition-metal (TM) doped anatase TiO$_2$. By Li intercalation, Mn-doped TiO$_2$ exhibits the insulator to metal transition. On the other hand, Li-intercalated Fe-doped TiO$_2$ has the insulating ground state for low concentration of Li/Ti=0.067, but the metallic ground state for high concentration of Li/Ti=0.133. We discuss the $n$-type carrier induced ferromagnetism in Li-intercalated TM-doped anatase TiO$_2$. Based on the Li-intercalated TM-doped anatase TiO$_2$, we propose a potential spintr…
The electronic properties of pentavalent-ion (Nb$^{5+}$, Ta$^{5+}$, and I$^{5+}$) doped anatase and rutile TiO$_2$ are studied using spin-polarized GGA+\emph{U} calculations. Our calculated results indicate that these two phases of TiO$_2$ exhibit different conductive behavior upon doping. For doped anatase TiO$_2$, some up-spin-polarized Ti 3\emph{d} states lie near the conduction band bottom and cross the Fermi level, showing an \emph{n}-type half-metallic character. For doped rutile TiO$_2$, the Fermi level is pinned between two up-spin-polarized Ti 3\emph{d} gap states, showing an insulati…
TiO$_2$ anatase doped with Co has been recently reported to exhibit room-temperature ferromagnetism. $Ab$ $initio$ study on substitutional Co doping, however, yielded much larger magnetic moment for Co than experiment. Our calculations based on density-functional theory show that the substitutional Co ions incorporated into TiO$_2$ anatase tend to cluster and then the neighboring interstitial tetrahedral sites become energetically favorable for Co to reside, yielding a local environment more like Co$_3$O$_4$ than CoTiO$_3$. The interstitial Co destroys the spin-polarization of the surrounding …
The effects of $n$-type carrier doping by Li intercalation on magnetism in undoped and Co-doped anatase TiO$_2$ are investigated. We have found that doped $n$-type carriers in TiO$_2$ are localized mainly at Ti sites near the intercalated Li. With increasing the intercalation, local spins are realized at Ti. In the case of Co-doped TiO$_2$, most of the added $n$-type carriers fill the Co 3$d$ bands and the rest are localized at Ti. Therefore, Co magnetic moment vanishes by Li intercalation to have a nonmagnetic ground state.
We report a first-principles study on the geometric, electronic and magnetic properties of V-doped anatase TiO$_{2}$. The DFT+U (Hubbard coefficient) approach predicts semiconductor band structures for Ti$_{1-x}$V$_{x}$O$_{2}$ (x=6.25 and 12.5%), in good agreement with the poor conductivity of samples, while the standard calculation within generalized gradient approximation fails. Theoretical results show that V atoms tend to stay close and result in strong ferromagnetism through superexchange interactions. Oxygen vacancy induced magnetic polaron could produce long-range ferromagnetic interact…
We have investigated electronic structures of a room temperature diluted magnetic semiconductor : Co-doped anatase $\rm TiO_{2}$. We have obtained the half-metallic ground state in the local-spin-density approximation(LSDA) but the insulating ground state in the LSDA+$U$+SO incorporating the spin-orbit interaction. In the stoichiometric case, the low spin state of Co is realized with the substantially large orbital moment. However, in the presence of oxygen vacancies near Co, the spin state of Co becomes intermediate. The ferromagnetisms in the metallic and insulating phases are accounted for …
TiO$_2$ anatase has its significant importance in energy and environmental research. However, the major drawback of this immensely popular semi-conductor is its large bandgap of 3.2 eV. Several non-metals have been doped experimentally for extending the TiO$_2$ photo-absorption to the visible region. Providing in-depth theoretical guidance to the experimentalists to understand the optical properties of the doped system is therefore extremely important. We report here using state-of-the-art hybrid density functional approach and many body perturbation theory (within the frame work of GW and BSE…
Thin films of Ti1-xCoxO2 (x=0 and 0.03) have been prepared on sapphire substrates by spin-on technique starting from metalorganic precursors. When heat treated in air at 550 and 700 C respectively, these films present pure anatase and rutile structures as shown both by X-ray diffraction and Raman spectroscopy. Optical absorption indicate a high degree of transparency in the visible region. Such films show a very small magnetic moment at 300 K. However, when the anatase and the rutile films are annealed in a vacuum of 1x10-5 Torr at 500 oC and 600 oC respectively, the magnetic moment, at 300 K,…
We report first-principles microscopic calculations of the formation energy, electrical activity, and magnetic moment of Co dopants and a variety of native defects in TiO2 anatase. Using these results, we use equilibrium thermodynamics to predict the resulting carrier concentration, the average magnetic moment per Co, and the dominant oxidation state of Co. The predicted values are in good agreement with experiment under the assumption of O-poor growth conditions. In this regime, a substantial fraction of Co dopants occupy interstitial sites as donors. The incomplete compensation of these dono…
We develop a first-principles approach based on many-body perturbation theory to investigate the effects of the interaction between electrons and carrier plasmons on the electronic properties of highly-doped semiconductors and oxides. Through the evaluation of the electron self-energy, we account simultaneously for electron-plasmon and electron-phonon coupling in theoretical calculations of angle-resolved photoemission spectra, electron linewidths, and relaxation times. We apply this methodology to electron-doped anatase TiO2 as an illustrative example. The simulated spectra indicate that elec…
The Co-doped anatase TiO$_{2}$, a recently discovered room-temperature ferromagnetic insulator, has been studied by the first-principles calculations in the pseudo-potential plane-wave formalism within the local-spin-density approximation (LSDA), supplemented by the full-potential linear augmented plane wave (FP-LAPW) method. Emphasis is placed on the dependence of its electronic structures and linear optical properties on the Co-doping concentration and oxygen vacancy in the system in order to pursue the origin of its ferromagnetism. In the case of substitutional doping of Co for Ti, our calc…
In this work, electronic structure of several doped TiO$_2$ anatase systems is computed using DFT+$U$. Effective masses of charge carriers are also computed to quantify how the dopant atoms perturb the bands of the host anatase material. $U$ is computed systematically for all the dopants using the linear response method rather than using fitting procedures to physically known quantities. A combination of $d$ and $f$ block elements (Nb, Ta, V, Mo, W, Cr, La, Cu, Co and Ce) are considered as dopants. Depending upon the energies of their outer $d$ or $f$ electrons, the dopants are found to form d…
Temperature-programmed reduction and dispersive X-ray absorption spectroscopy studies of CeO2-based nanopowders for intermediate-temperature Solid-Oxide Fuel Cell anodes
CONICET / Laboratorio de Cristalografía Aplicada, Escuela de Ciencia y Tecnología, Universidad Nacional de General San Martín（阿根廷国家科学技术研究委员会/应用晶体学实验室，科学与技术学院，圣马丁国立大学）；Departamento de Física de la Materia Condensada, Gerencia de Investigación y Aplicaciones, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica（凝聚态物理系，研究与应用程序管理部，宪法原子中心，阿根廷国家原子能委员会）；Instituto de Nanociencia y Nanotecnología (INN), CNEA-CONICET（纳米科学与纳米技术研究所（INN），阿根廷国家原子能委员会-阿根廷国家科学技术研究委员会）；UNIDEF-CONICET-MINDEF, Departamento de Investigaciones en Sólidos, CITEDEF（国防大学-阿根廷国家科学技术研究委员会-国防部，固体研究系，国防工业技术中心）；Instituto de Investigación e Ingeniería Ambiental, Universidad Nacional de General San Martín（环境研究与工程学院，圣马丁国立大学）
Ab-initio density functional theory (DFT) calculations of the relative stability of anatase and rutile polymorphs of TiO2 were carried using all-electron atomic orbitals methods with local density approximation (LDA). The rutile phase exhibited a moderate margin of stability of ~ 3 meV relative to the anatase phase in pristine material. From computational analysis of the formation energies of Si, Al, Fe and F dopants of various charge states across different Fermi level energies in anatase and in rutile, it was found that the cationic dopants are most stable in Ti substitutional lattice positi…
In this work we present an X-ray Absorption Spectroscopy characterization of the local environment of the impurity in room temperature ferromagnetic anatase TiO2 thin films doped with Co, Ni, Cu, or Zn, deposited on LaAlO3 substrate by Pulsed Laser Deposition. It was found that there is a considerable amount of impurity atoms substituting Ti in TiO2 anatase, although the presence of metal transition monoxide clusters can not be discarded. From our results we infer that the observed room temperature ferromagnetism of the samples could be assigned to the metal transition atoms replacing Ti in Ti…
We studied the electronic and atomic structures of anatase TiO2 codoped with Cr and N using hybrid density functional theory calculations. Nonlocal screened Hartree-Fock exchange energy is partially mixed with traditional semilocal exchange part. This not only heals the band gap underestimation but also improves the description of anion/cation-driven impurity states and magnetization of the dopants. Cr and/or N doping modifies the valence and conduction band edges of TiO2 leading to significant band gap reduction. Hence, Cr, N and Cr-N doped TiO2 are promising for enhanced photoactivity.
Magneto-optical spectroscopy of a transparent ferromagnetic semiconductor, anatase TiO2 doped with Co, is carried out at room temperature. A large magneto-optical response with ferromagnetic field dependence is observed throughout from ultraviolet to visible range and increases with increasing Co content or carrier concentration. The magnitude of magnetic circular dichroism (MCD) per unit thickness has a peak around the absorption edge such a huge value of ~10400 degree/cm at 3.57 eV for a 10 mol% Co-doped specimen. Although the results are not sufficient to prove that the ferromagnetism is in…
We report on the optical properties of magnetic cobalt-doped anatase phase titanium dioxide Ti_{1-x}Co_{x}O_{2-d} films for low doping concentrations, 0 <= x <= 0.02, in the spectral range 0.2 to 5 eV. For well oxygenated films (d << 1) the optical conductivity is characterized by an absence of optical absorption below an onset of interband transitions at 3.6 eV and a blue shift of the optical band edge with increasing Co concentration. The absence of below band gap absorption is inconsistent with theoretical models which contain midgap magnetic impurity bands and suggests that strong on-site …
We perform first-principles calculations to investigate the band structure, density of states, optical absorption, and the imaginary part of dielectric function of Cu, Ag, and Au-doped anatase TiO2 in 72 atoms systems. The electronic structure results show that the Cu incorporation can lead to the enhancement of d states near the uppermost of valence band, while the Ag and Au doping cause some new electronic states in band gap of TiO2. Meanwhile, it is found that the visible optical absorptions of Cu, Ag, and Au-doped TiO2, are observed by analyzing the results of optical properties,.which loc…
An external electric field induced reversible modulation of room temperature magnetic moment is achieved in an epitaxial and insulating thin film of dilutely cobalt-doped anatase TiO2. This first demonstration of electric field effect in any oxide based diluted ferromagnet is realized in a high quality epitaxial heterostructure of PbZr0.2Ti0.8O3/Co:TiO2/SrRuO3 grown on (001) LaAlO3. The observed effect, which is about 15% in strength in a given heterostructure, can be modulated over several cycles. Possible mechanisms for electric field induced modulation of insulating ferromagnetism are discu…
It is shown that dilute niobium doping has significant effect on the ferromagnetism and microstructure of dilutely cobalt-doped anatase TiO2 films. Epitaxial films of anatase TiO2 with 3% Co, without and with 1% niobium doping were grown by pulsed-laser deposition at 875 C at different oxygen pressures. For growth at 10^{-5} Torr niobium doping suppresses the ferromagnetism, while it enhances the same in films grown at 10^{-4} Torr. High-resolution Z-contrast Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy show uniform surface segregation of cobalt-rich Ti_{1-x-…
We present the results of Raman and photoluminescence (PL) studies on epitaxial anatase phase Ti$_{1-x}$Co$_x$O$_2$ films for $x$ = 0-0.07, grown by pulsed laser deposition. The low doped system ($x$=0.01 and 0.02) shows a Curie temperature of ~700 K in the as-grown state. The Raman spectra from the doped and undoped films confirm their anatase phase. The photoluminescence spectrum is characterized by a broad emission from self-trapped excitons (STE) at 2.3 eV at temperatures below 120 K. This peak is characteristic of the anatase-phase TiO$_2$ and shows a small blueshift with increasing dopin…
Electronic properties and atomic structures of W, N, S, W/N, and W/S dopings of anatase TiO_2 have been systematically investigated using the density functional theory (DFT). The exchange and correlation effects have been treated with Heyd, Scuseria and Ernzerhof (HSE) hybrid functional. Mixing traditional semi-local and non-local screened Hartree-Fock (HF) exchange energies, the HSE method corrects the band gap and also improves the description of anion/cation derived gap states. Enhanced charge carrier dynamics, observed for W/N codoped titania, can partly be explained by the passivative mod…
Combining LSDA+$U$ and an analysis of superexchange interactions beyond DFT, we describe the magnetic ground states in rutile and anatase Cr-doped TiO$_2$. In parallel, we correct our LSDA+$U$ ground state through GW corrections ($GW$@LSDA+$U$) that reproduce the position of impurity states and the band gaps in satisfying agreement with experiments. Because of the different topological coordinations of Cr-Cr bonds in the ground states of rutile and anatase, superexchange interactions induce either ferromagnetic or antiferromagnetic couplings of Cr ions. In Cr-doped anatase, this interaction le…
Oxygen (O2) adsorbed on metal oxides is important in catalytic oxidation reactions, chemical sensing, and photocatalysis. Strong adsorption requires transfer of negative charge from oxygen vacancies (VOs) or dopants, for example. With scanning tunneling microscopy, we observed, transformed, and, in conjunction with theory, identified the nature of O2 molecules on the (101) surface of anatase (titanium oxide, TiO2) doped with niobium. VOs reside exclusively in the bulk, but we pull them to the surface with a strongly negatively charged scanning tunneling microscope tip. O2 adsorbed as superoxo …
Copper dopants are varyingly reported to enhance photocatalytic activity at titanium dioxide surfaces through uncertain mechanisms. In order to interpret how copper doping might alter the performance of titanium dioxide photocatalysts in aqueous media we applied density functional theory methods to simulate surface units of doped anatase (101) planes. By including van der Waals interactions, we consider the energetics of adsorbed water at anatase surfaces in pristine and copper doped systems. Simulation results indicate that copper dopant at anatase (101) surfaces is most stable in a 2+ oxidat…
In this paper, I demonstrate a density functional theory plus dynamical mean field theory study on the electronic properties of doped $TiO_2$ rutile as well as another tetragonal phase anatase with oxygen vacancy. The density of states and optical properties have been obtained from the electronic structure applying screened hybrid exchange correlation density functionals. All the single-particle excitations are treated within the dynamical mean field theory for independent quasiparticles. For optical properties, excitations are considered by solving the Bethe-Salpeter equation for Coulomb corr…
Anatase TiO$_2$ is among the most studied materials for light-energy conversion applications, but the nature of its fundamental charge excitations is still unknown. Yet it is crucial to establish whether light absorption creates uncorrelated electron-hole pairs or bound excitons and, in the latter case, to determine their character. Here, by combining steady-state angle-resolved photoemission spectroscopy and spectroscopic ellipsometry with state-of-the-art ab initio calculations, we demonstrate that the direct optical gap of single crystals is dominated by a strongly bound exciton rising over…
We carried out density functional theory calculations to model the electronic structure and the magnetic interactions in copper doped anatase and rutile titanium dioxide in order to shed light on the potential of these systems as magnetic oxides using different density functional schemes. In both polymorphs copper dopant was found to be most stable in substitutional lattice positions. Ferromagnetism is predicted to be stable well above room temperature with long range interactions prevailing in the anatase phase while the rutile phase exhibits only short range superexchange interaction among n…
We present a synthesis/processing method for fabricating ferrimagnetic insulator (Bi-doped yttrium iron garnet) thin films with tunable magnetic anisotropy. Since the desired magnetic properties rely on controllable thickness and successful doping, we pay attention to the entire synthesis/processing procedure (nanopowder synthesis, nanocrystalline target preparation and pulsed laser deposition (PLD)). Atomically flat films were deposited by PLD on (111)-orientated yttrium aluminum garnet. We show a significant enhancement of perpendicular anisotropy in the films, caused by strain-induced aniso…
We synthesized pure and Co-doped (6.25 12.5 at.) ZrO$_2$ nanopowders in order to study their magnetic properties.We analyzed magnetic behavior as a function of the amount of Co and the oxygenation, which was controlled by low pressure thermal treatments. As prepared pure and Co-doped samples are diamagnetic and paramagnetic respectively. Ferromagnetism can be induced by performing low pressure thermal treatments, which becomes stronger as the dwell time of the thermal treatment is increased. This behavior can be reversed, recovering the initial diamagnetic or paramagnetic behavior, by performi…
Thin TiO2 films on quartz substrates were prepared by spin coating of undoped and metal-ion-doped Sol Gel precursors. These films were characterised by Scanning Electron Microscopy, Laser Raman Microspectroscopy, Xray Diffraction and UV Vis Transmission. The photocatalytic performances of the films were assessed by the photo-degradation of methylene-blue in aqueous solution under UV irradiation. Films exhibited a high degree of orientation and a thermal stabilization of the anatase phase as a result of substrate effects. In the absence of dopants, the rutile phase formed as parallel bands in t…
A swift chemical route to synthesize Co-doped SnO$_2$ nanopowders is described. Pure and highly stable Sn$_{1-x}$Co$_x$O$_{2-δ}$ (0 $\le$ x $\le$ 0.15) crystalline nanoparticles were synthesized, with mean grain sizes < 5 nm and the dopant element homogeneously distributed in substitutional sites of the SnO$_2$ matrix. The UV-visible diffuse reflectance spectra of the Sn$_{1-x}$Co$_x$O$_{2-δ}$ samples reveal red shifts, the optical bandgap energies decreasing with increasing Co concentration. The Urbach energies of the samples were calculated and correlated with their bandgap energies. The pho…
Colloidal cobalt-doped TiO2 (anatase) nanocrystals were synthesized and studied by electronic absorption, magnetic circular dichroism, transmission electron microscopy, magnetic susceptibility, cobalt K-shell X-ray absorption spectroscopy, and extended X-ray absorption fine structure measurements. The nanocrystals were paramagnetic when isolated by surface-passivating ligands, weakly ferromagnetic (Ms = 1.5 x 10-3 mB/Co2+ at 300 K) when aggregated, and strongly ferromagnetic (up to Ms = 1.9 mB/Co2+ at 300 K) when spin-coated into nanocrystalline films. X-ray absorption data reveal that cobalt …
Defined substoichiometric titanium oxides (Ti$_x$O$_{2x-1}$ with $3 < x < 10$) called Magneli phases have been investigated mostly for their unusual high conductivity and metal-like behavior. In photocatalysis, Magneli phase containing titania particles have been reported to provide favorable charge separation resulting in enhanced reaction efficiency. In the current work we describe a one-step synthesis of Magneli-containing mixed phase nanoparticles that carry directly integrated minute amounts of Pt. Phase optimized nanoparticles that contain only a few hundred ppm Pt are very effective pho…
Among the wide bandgap semiconductors, TiO$_{2}$ is the highly stable and cost-efficient semiconductor used for the different photocatalysis processes like water splitting, chemical waste degradation, anti-micro bacterial activities, and more. Materials showing high hydrophilicity (surface phenomenon) with low bandgap are required to improve photocatalysis efficiency. We report the synthesis of Zn (4 wt.%) and N (4 wt.%) doped TiO$_{2}$ thin films using the spin coating technique to improve surface wettability. The XRD pattern shows the growth of the pure anatase phase of TiO$_{2}$. UV absorpt…
Samples of nitrogen-doped titanium dioxide (anatase, $0.2 \leq N \leq 1.0~wt\%$) prepared by the sol-gel method were investigated using X-band EPR spectroscopy, photoconductivity and photocatalysis measurements. $N\bullet$ and $NO\bullet$ paramagnetic defects in N-TiO2 have been observed; their concentrations and spin-Hamiltonian parameters were calculated. An increase both in the rate of the generation of free charge carriers and in the rate of photocatalysis was found in N-TiO2 in contrast with non-doped titania under visible light. The correlation of the density of the observed radicals wit…
Electronic structures and optical properties of C-N-codoped anatase TiO2 were calculated by using GGA+U method based on the density functional theory. The calculated results showed that the N-doped, C-doped, and C-N-codoped TiO2 produced 2p states in band gap, and the band gaps of the three doped systems decreased compared with the pure TiO2. According to the optical results, the band edges of the three doped systems shifted to the long wavelength region, and the visible optical absorption from 450 to 800 nm was observed. Moreover, the visible light response of C-N-codoped TiO2 was better than…
Thin films of Co-TiO2 are deposited on silicon and quartz substrates using Pulse Laser Deposition (PLD) process at various oxygen partial pressures ranging from 6.6 x 10-3 Pascals (Pa) to 53 Pa. Crystal structure, transport and magnetic properties of reduced CoxTi(1-x)O2 (0 <x< 0.03) thin films are investigated and are found to have a strong dependence on the oxygen partial pressure. X-ray diffraction (XRD) data reveals the presence of mixed phase material containing both anatase and rutile. However, these phases intertransform with the change in the oxygen partial pressure in the chamber duri…
This paper reports on the structural and optical properties of Co-doped TiO2 thin films grown onto (0001) Al2O3 substrates by non-reactive pulsed laser deposition (PLD) using argon as buffer gas. It is shown that by keeping constant the substrate temperature at as low as 310 C and varying only the background gas pressure between 7 Pa and 70 Pa, it is possible to grow either epitaxial rutile or pure anatase thin films, as well as films with a mixture of both polymorphs. The optical band gaps of the films are red shifted in comparison to the values usually reported for undoped TiO2, which is con…
The transition metal ions doped with TiO2 films are of magnetic properties at room temperatures and have stimulated many scientists to study other properties. The Co-TiO2 sandwich composite films have been recently grown on glass and silicon substrates by using alternately radio frequency reactive and direct current magnetron sputtering. The microstructural properties of these films were characterized with Raman spectra and X-ray photoemission spectra (XPS). It shows an anatase TiO2 containing Co nano-layer. Optical absorption spectra have red shift with Co nano-layer increasing, which origina…
Titanium-based oxides are abundant, chemically stable, non-toxic, and highly versatile materials, with applications ranging from photovoltaics to catalysis. For rutile and anatase phases of Titanium dioxide (TiO2), the bandgap ranges from 3.0-3.2 eV, which are too large to absorb in the visible range (400 nm - 700 nm), resulting in poor photo-catalytic efficiency. Nitrogen doping into TiO2 has been able to narrow its bandgap, forming an absorption tail in the visible-light region. However, TiO2 has limits to which it can be doped, suggesting investigations of the oxygen-deficient Ti203. Using …
