First-principles study of Oxygen deficiency in rutile Titanium Dioxide

2011 ◽  
Vol 1352 ◽  
Author(s):  
Hsin-Yi Lee ◽  
Stewart J. Clark ◽  
John Robertson
Keyword(s):  
Oxygen Vacancy ◽  
Band Gap ◽  
Defect Formation ◽  
Chemical Potential ◽  
Oxygen Deficiency ◽  
Energy Levels ◽  
Hybrid Functional ◽  
Charge Densities ◽  
Screened Exchange ◽  
Rutile Titanium Dioxide

ABSTRACTThe energy levels of the different charge states of an oxygen vacancy and titanium interstitial in rutile TiO2 were calculated using the screened exchange (sX) hybrid functional [1]. The sX method gives 3.1 eV for the band gap of rutile TiO2, which is close to the experimental value. We report the defect formation energy of the oxygen deficient structure. It is found that the defect formation energies, for the neutral charge state, of oxygen vacancy and titanium interstitial are quite similar, 2.40 eV and 2.45 eV respectively, for an oxygen chemical potential of the O-poor condition. The similar size of these two calculated energies indicates that both are a cause of oxygen deficiency, as observed experimentally [2]. The transition energy level of oxygen vacancy lies within the band gap, corresponding to the electrons located at adjacent titanium sites. The sX method gives a correct description of the localization of defect charge densities, which is not the case for GGA [3-6].

Study on the optical spectra of the oxygen vacancy in ZnWO4 crystal

2021 ◽  
pp. 2150471
Author(s):  
Gaiping Lian ◽  
Tingyu Liu ◽  
Le Yu
Keyword(s):  
Oxygen Vacancy ◽  
Density Functional ◽  
Defect Formation ◽  
Finite Size ◽  
Optical Spectra ◽  
Functional Method ◽  
Hybrid Functional ◽  
Electron Phonon Coupling ◽  
Correction Scheme ◽  
The Density Functional Theory

ZnWO4 is easy to color, which will reduce the luminous efficiency of the crystal and limit the application of the crystal. In order to study the origin of the color in the crystal, in this paper, the effects of the oxygen vacancy on the optical properties for the ZnWO4 crystal have been studied based on the density functional theory (DFT). The hybrid functional method (HSE) and the finite-size correction scheme (FNV) are used to correct the band edge problem and eliminate the artificial interaction of the charged defects, respectively. On the basis of the corrected defect formation energy, we obtain the optical spectra of the [Formula: see text] and [Formula: see text] centers containing electron-phonon coupling. The calculated absorption and luminescence peaks are at 2.54 eV and 0.79 eV for the [Formula: see text] center and at 2.98 eV and 1.09 eV for the [Formula: see text] center, respectively. The calculated absorption band of the [Formula: see text] center is close to the experimental value of 2.48 eV (500 nm), so we speculate that the coloring of the ZnWO4 crystal is related to the [Formula: see text] center. Meanwhile, the existence of oxygen vacancy makes ZnWO4 crystal to have self-absorption and to increase decay time, which greatly affects the scintillation properties of the crystal.

Defect Energy Levels in HfO2, ZrO2, La2O3 and SrTiO3

2004 ◽  
Vol 811 ◽  
Author(s):  
K Xiong ◽  
P W Peacock ◽  
J Robertson
Keyword(s):  
Band Gap ◽  
Oxygen Vacancies ◽  
Energy Levels ◽  
Density Approximation ◽  
Weighted Density ◽  
Defect Energy ◽  
High K ◽  
Screened Exchange ◽  
Weighted Density Approximation

AbstractDefect energy levels of oxygen vacancies in various high K oxides HfO2, ZrO2, La2O3 and SrTiO3 have been calculated using methods which give the correct band gap, such as the screened exchange and weighted density approximation.

scholarly journals The Effect of Defect Disorder on the Electronic Structure of Rutile TiO2-x

2006 ◽  
Vol 251-252 ◽  
pp. 1-12 ◽  
Author(s):  
Faruque M. Hossain ◽  
Graeme E. Murch ◽  
L. Sheppard ◽  
Janusz Nowotny
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Point Defects ◽  
Density Functional ◽  
Defect Formation ◽  
Energy Levels ◽  
Defect Energy ◽  
Defect Disorder ◽  
Effect Of Oxygen ◽  
Formation Energies

The purpose of this work is to study the effect of bulk point defects on the electronic structure of rutile TiO2. The paper is focused on the effect of oxygen nonstoichiometry in the form of oxygen vacancies, Ti interstitials and Ti vacancies and related defect disorder on the band gap width and on the local energy levels inside the band gap. Ab initio density functional theory is used to calculate the formation energies of such intrinsic defects and to detect the positions of these defect induced energy levels in order to visualize the tendency of forming local mid-gap bands. Apart from the formation energy of the Ti vacancies (where experimental data do not exist) our calculated results of the defect formation energies are in fair agreement with the experimental results and the defect energy levels consistently support the experimental observations. The calculated results indicate that the exact position of defect energy levels depends on the estimated band gap and also the charge state of the point defects of TiO2.

Electronic structures and optical properties of cuprous oxide and hydroxide

2014 ◽  
Vol 1675 ◽  
pp. 185-190
Author(s):  
Yunguo Li ◽  
Cláudio M. Lousada ◽  
Pavel A. Korzhavyi
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Cuprous Oxide ◽  
Density Functional ◽  
Spent Nuclear Fuel ◽  
Energy Levels ◽  
Chemical Properties ◽  
Density Functional Theory Calculations ◽  
Hybrid Functional ◽  
Indirect Band Gap

ABSTRACTThe broad range of applications of copper, including areas such as electronics, fuel cells, and spent nuclear fuel disposal, require accurate description of the physical and chemical properties of copper compounds. Within some of these applications, cuprous hydroxide is a compound whose relevance has been recently discovered. Its existence in the solid-state form was recently reported. Experimental determination of its physical-chemical properties is challenging due to its instability and poop crystallinity. Within the framework of density functional theory calculations (DFT), we investigated the nature of bonding, electronic spectra, and optical properties of the cuprous oxide and cuprous hydroxide. It is found that the hybrid functional PBE0 can accurately describe the electronic structure and optical properties of these two copper(I) compounds. The calculated properties of cuprous oxide are in good agreement with the experimental data and other theoretical results. The structure of cuprous hydroxide can be deduced from that of cuprous oxide by substituting half Cu+ in Cu2O lattice with protons. Compared to Cu2O, the presence of hydrogen in CuOH has little effect on the ionic nature of Cu–O bonding, but lowers the energy levels of the occupied states. Thus, CuOH is calculated to have a wider indirect band gap of 2.73 eV compared with the Cu2O band gap of 2.17 eV.

Tuning the electronic and structural properties of WO3 nanocrystals by varying transition metal tungstate precursors

RSC Advances ◽  
2014 ◽  
Vol 4 (107) ◽  
pp. 62423-62429 ◽  
Author(s):  
Sara Rahimnejad ◽  
Jing Hui He ◽  
Wei Chen ◽  
Kai Wu ◽  
Guo Qin Xu
Keyword(s):  
Methylene Blue ◽  
Transition Metal ◽  
Oxygen Vacancy ◽  
Band Gap ◽  
Azo Dye ◽  
Electron Hole ◽  
Recombination Time ◽  
Metal Tungstate ◽  
Electronic And Structural Properties ◽  
Hole Recombination

WO3 nanoplates derived from NiWO4 were found to have the highest concentration of oxygen vacancy, narrowest band gap, longest electron–hole recombination time, and in turn the highest rate of photodegradation of azo dye methylene blue.

High photovoltage achieved in low band gap polymer solar cells by adjusting energy levels of a polymer with the LUMOs of fullerene derivatives

2008 ◽  
Vol 18 (45) ◽  
pp. 5468 ◽  
Author(s):  
Fengling Zhang ◽  
Johan Bijleveld ◽  
Erik Perzon ◽  
Kristofer Tvingstedt ◽  
Sophie Barrau ◽  
...  
Keyword(s):  
Solar Cells ◽  
Band Gap ◽  
Polymer Solar Cells ◽  
Energy Levels ◽  
Low Band Gap ◽  
Fullerene Derivatives ◽  
Low Band Gap Polymer

Defect Formation by Ion Implantation in Cz-Si Studied by a Monoenergetic Positron Beam

1992 ◽  
Vol 262 ◽  
Author(s):  
A. Uedono ◽  
Y. Ujihira ◽  
L. Wei ◽  
Y. Tabuki ◽  
S. Tanigawa ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Ion Implantation ◽  
Defect Formation ◽  
Positron Beam ◽  
Low Energy ◽  
Doppler Broadening ◽  
Positron Energy ◽  
Annealing Experiments ◽  
Incident Positron ◽  
Ion Implanted

ABSTRACTVacancy-type defects in ion implanted Si were studied by a monoenergetic positron beam. The depth-distributions of the defects were obtained from measurements of Doppler broadening profiles of the positron annihilation as a function of incident positron energy. The results showed that a size of vacany-clusters introduced by 150-keV P+-ion implantation was found to be smaller than that introduced by 2-MeV P+-ion implantation. This was attributed to an overlap of collision cascades in low-energy (150 keV) ion implanted specimens. From isochronal annealing experiments for 80-keV B+- and 150-keV P+-ion implanted specimens, the defected region was removed by 1200 °C annealing, however, for 2-MeV P+-implanted specimen, two-types of oxygen-vacancy complexes were found to coexist even after 1200 °C annealing.

Structural and Electronic Properties of Oxygen Vacancies in Monoclinic HfO2

2007 ◽  
Vol 996 ◽  
Author(s):  
Peter Broqvist ◽  
Alfredo Pasquarello
Keyword(s):  
Oxygen Vacancy ◽  
Optical Absorption ◽  
Total Energy ◽  
Band Gap ◽  
Electronic Properties ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Structural And Electronic Properties ◽  
Defect Levels ◽  
Hybrid Density Functional

AbstractWe study structural and electronic properties of the oxygen vacancy in monoclinic HfO2 for five different charge states. We use a hybrid density functional to accurately reproduce the experimental band gap. To compare with measured defect levels, we determine total-energy differences appropriate to the considered experiments. Our results show that the oxygen vacancy can consistently account for the defect levels observed in optical absorption, direct electron injection, and trap-assisted conduction experiments.

Nonspectroscopic approach to the determination of the chemical potential and band-gap renormalization in quantum wells

1992 ◽  
Vol 45 (15) ◽  
pp. 8535-8541 ◽  
Author(s):  
E. H. Böttcher ◽  
N. Kirstaedter ◽  
M. Grundmann ◽  
D. Bimberg ◽  
R. Zimmermann ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Band Gap ◽  
Chemical Potential
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