Search results for "OXYGEN VACANCY"
showing 10 items of 12 documents
Ab Initio Thermodynamics of Oxygen Vacancies and Zinc Interstitials in ZnO.
2015
ZnO is an important wide band gap semiconductor with potential application in various optoelectronic devices. In the current contribution, we explore the thermodynamics of oxygen vacancies and zinc interstitials in ZnO from first-principles phonon calculations. Formation enthalpies are evaluated using hybrid DFT calculations, and phonons are addressed using the PBE and the PBE+U functionals. The phonon contribution to the entropy is most dominant for oxygen vacancies, and their Gibbs formation energy increases when including phonons. Finally, inclusion of phonons decreases the Gibbs formation energy difference of the two defects and is therefore important when predicting their equilibrium c…
Negative U‐properties of the oxygen‐vacancy in ZnO
2006
It is shown that the intensity of the oxygen vacancy (VO) related emission in ZnO at 2.45 eV correlates to the concentration of the donor level E4. E4 is located 530 meV below the conduction band and attributed to the VO0/++ recharging. Deep level transient spectroscopy (DLTS) experiments with optical excitation locate the VO2+/+ level position 140 meV below the conduction band and give evidence for the “negative- U” properties of the oxygen vacancies in ZnO. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
EPR on Radiation-Induced Defects in SiO2
2014
Continuous-wave electron paramagnetic resonance (EPR) spectroscopy has been the technique of choice for the studies of radiation-induced defects in silica (SiO2) for 60 years, and has recently been expanded to include more sophisticated techniques such as high-frequency EPR, pulse electron nuclear double resonance (ENDOR), and pulse electron spin echo envelope modulation (ESEEM) spectroscopy. Structural models of radiation-induced defects obtained from single-crystal EPR analyses of crystalline SiO2 (alfa-quartz) are often applicable to their respective analogues in amorphous silica (a-SiO2), although significant differences are common.
Sr Doping and Oxygen Vacancy Formation in La1−xSrxScO3−δ Solid Solutions: Computational Modelling
2022
The study was performed with the financial support from the Latvian Council of Science under the grant agreement LZP-2020/2-0009. Calculations were performed at the HLRS, University of Stuttgart, within the project 12939 DEFTD. The Institute of Solid State Physics, University of Latvia (Latvia), as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Frame-work Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART2.
First principles calculations on CeO2 doped with Tb3+ ions
2019
This research was funded by the Latvian Council of Science (under the grant project lzp-2018/1-0147). Authors thank W. Chueh, J. Serra, R. Merkle, A. Popov for fruitful discussions.
First principles calculations of oxygen vacancy formation and migration in mixed conducting Ba0.5Sr0.5Co1−yFeyO3−δ perovskites
2011
Abstract First-principles supercell calculations of oxygen vacancies in the Ba 0.5 Sr 0.5 Co 1− y Fe y O 3− δ (BSCF) perovskites are presented. The density of states is determined for different iron content and oxygen vacancy concentrations, and the characteristic differences for Co and Fe are discussed. We analyze the dependences of the defect (oxygen vacancy) formation and migration energies on the Fe content and compare the calculated properties with those of related LaCoO 3 and LaFeO 3 perovskites.
Adsorbate-Induced Oxygen Vacancy Mobility in Ultrathin Oxide Films
2013
Oxides at the nanometric scale show a behavior markedly different from that of their bulk counterparts. Ultrathin oxides grown on metals do not reach the full insulator regime, and they cannot decouple the electronic clouds of incoming adsorbates from that of the metal substrate. Although oxygen vacancies control the chemical and physical properties of ultrathin oxide films, the role of intrinsic defects has been overlooked so far. By means of density functional theory methods, we show that the addition of atoms with high electron affinity, such as Au, to ultrathin MgO grown either on a Ag or Mo support, completely reverses the preferential positions of oxygen vacancies, decreases their res…
Diffusion-controlled annihilation and aggregation of F-centers in thermochemically reduced MgO crystals
2002
Abstract The dynamics of F-center (an oxygen vacancy which has trapped two electrons) aggregation in thermochemically reduced MgO single crystals with an exceptionally high F-center concentration (6×1018 cm−3) is discussed. A theory of the Mg nanocavity formation process is developed based on diffusion-controlled aggregation of elastically interacting F centers and their annihilation at traps. We show that in contrast to the generally accepted viewpoint, the F centers in the bulk are not annealed out at the external sample surface but at internal defects, such as dislocations, subgrain boundaries and impurities. The mutual attraction of the F centers is a key factor controlling the aggregat…
Use of site symmetry in supercell models of defective crystals: Polarons in CeO2
2017
The authors thank R. Merkle and G. W. Watson for stimulating discussions. E. K. also acknowledges partial financial support from the Russian Science Foundation for the study of charged defects under the project 14-43-00052. A. C. also acknowledges financial support from the University of Latvia Foundation (Arnis Riekstins's "MikroTik" donation). E. K. and D. G. express their gratitude to the High Performance Computer Centre in Stuttgart (HLRS, project DEFTD 12939) for the provided computer facilities whereas R. A. E. thanks the St. Petersburg State University Computer Center for assistance in high-performance calculations.
Vacancy Defects in Ga2O3: First-Principles Calculations of Electronic Structure
2021
This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP08856540) as well as by the Latvian research council via the Latvian National Research Program under the topic ?High-Energy Physics and Accelerator Technologies?, Agreement No: VPP-IZM-CERN-2020/1-0002 for A.I. Popov. In addition, J. Purans is grateful to the ERAF project 1.1.1.1/20/A/057 while A. Platonenko was supported by Latvian Research Council No. LZP-2018/1-0214. The authors thank A. Lushchik and M. Lushchik for many useful discussions. The research was (partly) performed in the Institute of Solid State Physics, University of Latvia ISSP UL. ISSP UL as…