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1.
Using the first-principles methods,we study the formation energetics properties of intrinsic defects,and the charge doping properties of extrinsic defects in transparent conducting oxides CuCrO2.Intrinsic defects,some typical acceptortype,and donor-type extrinsic defects in their relevant charge state are considered.By systematically calculating the formation energies and transition energy,the results of calculation show that,V Cu,O i,and O Cu are the relevant intrinsic defects in CuCrO2 ;among these intrinsic defects,V Cu is the most efficient acceptor in CuCrO2.It is found that all the donor-type extrinsic defects have difficulty in inducing n-conductivity in CuCrO2 because of their deep transition energy level.For all the acceptor-type extrinsic defects,substituting Mg for Cr is the most prominent doping acceptor with relative shallow transition energy levels in CuCrO2.Our calculation results are expected to be a guide for preparing promising n-type and p-type materials in CuCrO2.  相似文献   

2.
Using the first-principles methods, we study the electronic structure, intrinsic and extrinsic defects doping in transparent conducting oxides CuGaO2. Intrinsic defects, acceptor-type and donor-type extrinsic defects in their relevant charge state are considered. The calculation result show that copper vacancy and oxygen interstitial are the relevant defects in CuGaO2. In addition, copper vacancy is the most efficient acceptor. Substituting Be for Ga is the prominent acceptor, and substituting Ca for Cu is the prominent donors in CuGaO2. Our calculation results are expected to be a guide for preparing n-type and p-type materials in CuGaO2.  相似文献   

3.
Using first-principles methods, we studied the extrinsic defects doping in transparent conducting oxides CuMO2 (MSc, Y). We chose Be, Mg, Ca, Si, Ge, Sn as extrinsic defects to substitute for M and Cu atoms. By systematically calculating the impurity formation energy and transition energy level, we find that BeCu is the most prominent extrinsic donor and CaM is the prominent extrinsic acceptor. In addition, we find that Mg atom substituting for Sc is the most prominent extrinsic acceptor in CuScO2. Our calculation results are expected to be a guide for preparing n-type and p-type materials through extrinsic doping in CuMO2 (MSc,Y).  相似文献   

4.
莫曼  曾纪术  何浩  张喨  杜龙  方志杰 《物理学报》2019,68(10):106102-106102
研制开发新型的光电材料对促进社会经济发展具有重要的科学意义和实用价值.利用宽禁带CuInO_2铟基材料实现全透明光电材料是目前深入研究的热点.通过基于密度泛函的第一性原理计算方法,本文计算出掺杂元素Mg, Be, Mn在CuInO_2的形成能.计算结果表明,施主类缺陷(如掺杂元素替代Cu原子或进入间隙位置)由于较高的形成能和较深的跃迁能级,很难在CuInO_2材料中出现N型导电;而受主缺陷中,在氧原子化学势极大的情况下, Mg原子替代In能成为CuInO_2理想的受主缺陷.计算结果可为制备性能优异的CuInO_2材料提供指导.  相似文献   

5.
The molecular statics method is used to study the formation of defects and water incorporation in Y2O3. The crystal structure, the isothermal compressibility, and the formation enthalpy of Y2O3 calculated with the chosen interaction potentials are in good agreement with the experimental data. The formation energies of intrinsic and impurity defects are evaluated. The binding energy of protons and oxygen vacancies with an acceptor impurity at different distances is calculated. Various water incorporation reactions in the oxide are examined, including the mechanisms involving oxygen interstitial sites and oxygen vacancies produced by the acceptor doping. It is shown that the water incorporation in pure Y2O3 is energetically less favorable than in the acceptor doped oxide.  相似文献   

6.
Comparative measurements have been made of optical absorption and photoluminescence of refined undoped and Cu in-diffused ZnTe single crystals. Strong increases in a bound exciton BE line near 2.375 eV previously identified with the electrically dominant point defect acceptor ‘a’, with binding energy EA ? 149 meV, suggests that this acceptor is substitutional CuZn. Similarly strong increases in a relatively broad band at slightly higher energy suggests the simultaneous incorporation of shallow donors, possibly interstital CuI. These findings indicate that intrinsic defects such as VZn neither control the Fermi level in refined ZnTe nor produce shallow acceptors with EA ? 250 meV, contrary to much previous speculation.  相似文献   

7.
Preliminary ab initio calculation of different point defects energy and electronic density of states have been performed on the prototype chalcopyrite semiconductor CuInSe2. The simulation method used is based on the density functional theory within the framework of pseudo-potentials and plane waves basis. The isolated neutral defects considered are: VCu, VIn, VSe, Cui, Ini, InCu, CuIn and the complex defects are 2Cui+CuIn, InCu+CuIn and 2VCu+InCu, some of which being computed for the first time by advanced ab initio techniques. In agreement with previous results, we show that some point defects (such as VCu) and pair defects (2VCu+InCu) have very low formation energies. Some energies of formation were found significantly lower than previous estimations. The comparison of the formation energies with the exchange correlation (LDA or GGA) is discussed. The perturbation induced by the presence of some of these ideal defects on the density of states is also presented.  相似文献   

8.
The emission of CuInS2 is studied as a function of the exact composition in terms of deviations from molecularity and stoichiometry. By means of temperature-dependent (4.2–220 K) and excitation-intensity-dependent measurements, the two broad emission bands usually present are correlated with donor-acceptor transitions. In In-rich material the acceptor is located at 0.10 eV above the valence band. This acceptor is ascribed to VCu. In Cu-rich CuInS2 the acceptor level is located at 0.15 eV above the valence band, which is attributed to either VIn or CuIn. Two donor levels are identified, their ionization energies being about 35 and 72 meV. These donors are present in both In and Cu-rich samples and may originate from either intrinsic defects or impurities (Fe). Also, the influence of quenching of the crystals as well as the effect of different crystal growth methods (melt-growth and vapour-growth) on the emission is studied.  相似文献   

9.
彭丽萍  夏正才  尹建武 《物理学报》2012,61(3):37103-037103
采用第一性原理的计算方法, 分别研究了金红石相和锐钛矿相TiO2各种缺陷态形成的类型, 以及几何结构、生长气氛和Fermi能级位置对缺陷形成能的影响, 从理论上预测产生点缺陷的实验条件. 重点是讨论带电点缺陷的形成能, 并对结果进行适当修正. 研究发现, 本征缺陷的类型和浓度对 TiO2的性能有一定的影响: 在富O条件下, TiO2容易形成VTi(Ti空位)缺陷; 在富Ti条件下, TiO2的Tii4+VO(O空位)缺陷将大量出现, 形成Schottky缺陷.  相似文献   

10.
Using the first-principles methods, we study the formation energeties and charge doping properties of the extrinsic substitutional defects in kaolinite. Especially, we choose Be, Mg, Ca, Fe, Cr, Mn, Cu, Zn as extrinsic defects to substitute for Al atoms. By systematically calculating the impurity formation energies and transition energy levels, we find that all group-Ⅱ defects introduce the relative shallow transition energy levels in kaolinite. Among them, MgAl has the shallowest transition energy level at 0.08 eV above the valence band maximum. The transition- elemental defects FeAl, CrAl, and MnAl are found to have relative low formation energies, suggesting their easy formation in kaolinite under natural surrounding conditions. Our calculations show that the defects CuAl and ZnAl have the high formation energies and deep transition energy levels, which exclude the possibility of their formation in natural kaolinite.  相似文献   

11.
Using first-principles electronic structure theory, we have calculated defect formation energies and defect transition levels in CuInSe2 and CuGaSe2. We show that (i) it is easy to form Cu vacancies in CuInSe2, and (ii) it is also relatively easy to form cation antisite defects (e.g. InCu) for this ternary compound. Consequently, defect pairs such as (2VCu+InCu) have a remarkably low formation enthalpy. As a result, the formation of a series of Cu-poor compounds (CPCs) such as CuIn5Se8 and CuIn3Se5, is explained as a repeat of (2VCu+InCu) pairs in CuInSe2. The very efficient p-type self-doping ability of CuInSe2 is explained by the easy formation of the shallow Cu vacancies. The electrically benign character of the natural defect in CuInSe2 is explained in terms of an electronic passivation of the by . For CuGaSe2, we find that (i) the native acceptor formation energies and transition energy levels are similar to that in CuInSe2, but the donor formation energy is larger in CuGaSe2. (ii) The GaCu donor level in CuGaSe2 is deeper than InCu donor level in CuInSe2, therefore, GaCu behaves as an electron trap in CuGaSe2, even when it is passivated by VCu. We have also calculated the band alignment between the CPCs and CuInSe2, showing that it could have significant effect on the solar cell performance.  相似文献   

12.
High quality Mn doped ZnO thin films were grown on c-plane Al2O3 by oxygen plasma assisted molecular beam epitaxy. Photoluminescence spectra were investigated on the ferromagnetic ZnMnO films. An additional emission located at ∼3.32 eV was observed on these ferromagnetic films for both as-grown and oxygen-annealed samples. It is assigned to the recombination of neutral acceptor bound excitons. The ionization energy of the acceptor was estimated to be 53–80 meV. The observed ferromagnetism was explained to relate with acceptor-type defects.  相似文献   

13.
Vanadium pentoxide (V2O5) is a promising cathode material for high‐performance lithium‐ion batteries (LIBs) because of its high specific capacity, low cost, and abundant source. However, the practical application of V2O5 in commercial LIBs is still hindered by its intrinsic low ionic diffusion coefficient and moderate electrical conductivity. In the past decades, progressive accomplishments have been achieved that rely on the synthesis of nanostructured materials, carbon hybridization, and cation doping. Generally, fabrication of nanostructured electrode materials can effectively decrease the ion and electron transport distances while carbon hybridization and cation doping are able to significantly increase the electrical conductivity and diffusion coefficient of Li+. Implementation of these strategies addresses the problems that are related to the ionic and electronic conductivity of V2O5. Accordingly, the electrochemical performances of V2O5‐based cathodes are significantly improved in terms of discharge capacity, cycling stability, and rate capability. In this review, the recent advances in the synthesis of V2O5‐based cathode materials are highlighted that focus on the fabrication of nanostructured materials, carbon hybridization, and cation doping.  相似文献   

14.
Neutron scattering has been used to measure the charge and spin structure in the YBa2Cu3O6+x superconductors. Incommensurate static charge ordering is found at low doping levels while only charge fluctuations are found at higher doping. The spin structure is complex with both a commensurate resonance and incommensurate structure observed at low temperatures. The scattering results are used to construct a phase diagram for stripes in the YBa2Cu3O6+x system.  相似文献   

15.
By means of thermogravimetric measurements, it has been possible to obtain information on the nature of the intrinsic and extrinsic defects of TiO2, NbO2 and solid solutions NbyTi1?yOx Pure TiO2 is an oxygen-deficient oxide The main defects are oxygen vacancies, doubly ionized V..o or singly ionized V.o, and interstitial titanium Ti3i NbO2 is a metal-deficient oxide The main defects are neutral niobium vacancies. The solid solutions NbyTi1?yOx may be divided into two groups If y > 0 04, the behavior is analogous to that of NbO2; with the same defects, but the width of the homogeneity range decreases with the titanium content and Nb0 04Ti0 96O2 is a stoichiometnc oxide If y < 004, the oxides are both metal deficient and oxygen deficient according to the oxygen partial pressure. We have particularly studied the solution Ti0 995Nb0 005O2 In the oxygen-deficient domain, the main defects are assumed to be neutral or singly ionized oxygen vacancies In the metal-deficient domain, the main defects are metal vacancies V4Ti From these results we have deduced the nature of intrinsic defects in TiO2 to be Schottky defects: 2V..O + V4T1.  相似文献   

16.
High resolution photoelectron spectra from transition metal ions in TiO2, V2O5, VO2, V2O3, MnO, Mn2O3, MnO2, Cr2O3, FeO, CoO, NiO, CuO, Cu2O, FeSrO3, and Cu doped CaTiO3 were re-examined using a constrained curve fitting approach. Effective fits of the multiplet splitting present could be attained for the oxides with unfilled 3d bands if multiple final states were assumed. The type of transitions implied, also suggest the classification of these oxides during core level photoelectron emission as either; Mott–Hubbard (V2O5, VO2, V2O3, Cr2O3, and FeO), intermediate (MnO, Mn2O3, and MnO2) or charge transfer type compounds (FeSrO3, CoO, NiO, CuO and Cu doped CaTiO3). These transitions along with relationships defining the splitting energy with respect to the total spin and binding energy are discussed.  相似文献   

17.
Work function (WF) of undoped and Gd-doped PbZrO3 (PZG) was determined during isothermal oxidation and reduction experiments at 400 and 500 °C in the P(O2) range between 10 and 2.1×104 Pa. The obtained results are discussed in terms of two competitive effects, such as (i) an acceptor-type effect due to oxygen chemisorption and its subsequent incorporation into the oxide lattice and (ii) donor-type effect due to p(O2)-induced structural transitions, such as decomposition of PbZrO3 resulting in the formation of a surface layer composed of PbO and ZrO2. Both effects have different rates of appearence and the effect on electrical potential. It was found that oxidation results in irreproducible changes of surface properties involving the formation of a low-dimensional surface layer.  相似文献   

18.
《Current Applied Physics》2015,15(11):1556-1561
In this paper, first-principles calculations have been implemented to study the structural relaxation, formation energies and electronic structure of Al doped α-MnO2. Both Al insertion and Al substitution reactions in the α-MnO2 were considered. Calculated formation energies indicate that Mn atom is easier to be displaced by Al atom under the O-rich growth condition compared with Al insertion reaction. Besides, it can be found that Al doping can afford acceptor impurity level which can accommodate electrons, thus contributing to the improvement of conductivity of α-MnO2. The conductivity of α-MnO2 is gradually improved with the increasing doping concentration of Al, and Al0.0417Mn0.9583O2 exhibits the best conductivity. Lastly, the electronic structure of Al0.0417Mn0.9583O2 was further investigated by analysis of total charge density and Bader charge. It is clear that Al doping can afford more electrons for α-MnO2, which also contributes to improvement of its conductivity.  相似文献   

19.
The electrical ionic conductivity of unirradiated and irradiated CaF2: Nd crystals in the range of 60 to 800°C has been measured. The conductivity plot is basically divided into four parts, i.e., intrinsic and extrinsic unassociated, extrinsic associated, and extrinsic segregated regions. Activation energy (for unirradiated samples) in the extrinsic unassociated region is in the range of 0.69 to 1.20 eV depending on the doping concentration while for the intrinsic region, it is of the order of 1.89 eV. The conductivity in the extrinsic unassociated region increases with increase of Nd content in the sample. Also, the conductivity in the extrinsic region forγ-irradiated sample is higher than that for unirradiated one. In the intrinsic region, however, the conductivity is independent of dopant concentration orγ-irradiation. From these results it is surmised thatF interstitials are the charge carriers in this region for CaF2: Nd3+ system.  相似文献   

20.
Through first-principles calculation using the screened hybrid functional, we investigate the energetics and electronic structure of substitutional hydrogen (HO) in which one hydrogen replaces an oxygen atom in LaAlO3. The calculated binding energy between the hydrogen and the oxygen vacancy (VO) indicates that HO is energetically likely to form in the oxide. HO releases one electron to the conduction band, so it is a shallow donor. Most importantly, HO completely eliminates the in-gap defect states associated with VO, suggesting that hydrogen can be used as passivating agent for VO acting as a carrier trap or fixed charge in the oxide and near the oxide/semiconductor interface in LaAlO3-based devices.  相似文献   

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