Theoretical investigation of Er-O co-doping in hexagonal GaN

2011 ◽  
Vol 1342 ◽  
Author(s):  
Simone Sanna ◽  
Uwe Gerstmann ◽  
Wolf Gero Schmidt
Keyword(s):  
Binding Energy ◽  
Density Functional ◽  
Electronic Charge ◽  
High Binding Energy ◽  
Oxygen Ions ◽  
Co Doping ◽  
Geometric Configurations ◽  
Similar Formation ◽  
Formation Energies ◽  
Co Doped

ABSTRACTThe co-doping of hexagonal GaN with Er and O is investigated by means of density functional calculations. Predominantly Er-O defect-pairs characterized by a binding energy around 0.5 eV are formed. Different geometric configurations with various orientations (i.e. axial and basal pairs with C3v or C1h symmetry) are expected with similar formation energies. Independent of the particular configuration, the presence of oxygen does not deeply affect the atomic structure and the electronic charge distribution around the Er centers. The relatively high binding energy suggests that Er-O pairs should survive thermal treatment. An investigation of the binding energy per bond indicates that on the other hand Er-Ox complexes (x=2,3,4) are not likely to be formed (differently from Er-O co-doped Si). Rather, as long as the oxygen fluence does not overtake the Er fluence, different oxygen ions will be bound to different Er-centers.

Bandgap control and optical properties of β-Si3N4 by single- and co-doping from a first-principles simulation

2018 ◽  
Vol 32 (14) ◽  
pp. 1850178 ◽  
Author(s):  
Xuefeng Lu ◽  
Xu Gao ◽  
Junqiang Ren ◽  
Cuixia Li ◽  
Xin Guo ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
First Principles ◽  
Density Functional ◽  
Formation Energy ◽  
Blue Shift ◽  
Functional Theory ◽  
Co Doping ◽  
Charge Density Difference ◽  
Co Doped

Bandgap tailoring of [Formula: see text]-Si3N4 is performed by single and co-doping by using density functional theory (DFT) of PBE functional and plane-wave pseudopotential method. The results reveal that a direct bandgap transfers into an indirect one when single-doped with As element. Also, a considerate decrease of bandgap to 0.221 eV and 0.315 eV is present for Al–P and As–P co-doped systems, respectively, exhibiting a representative semiconductor property that is characteristic for a narrower bandgap. Compared with other doped systems, Al-doped system with formation energy of 2.67 eV is present for a more stable structure. From charge density difference (CDD) maps, it is found that the blue area between co-doped atoms increases, illustrating an enhancement of covalent property for Al–P and Al–As bonds. Moreover, a slightly obvious “Blue shift” phenomenon can be obtained in Al, Al–P and Al–As doped systems, indicating an enhanced capacity of responses to light, which contributes to the insight for broader applications with regard to photoelectric devices.

scholarly journals First-Principles Study of Molecular Adsorption of Hydrogen/s on Co-Adatom Graphene

2020 ◽  
Vol 25 (1) ◽  
pp. 15-23
Author(s):  
Nurapati Pantha ◽  
Saroj Thapa ◽  
Narayan Prasad Adhikari
Keyword(s):  
Magnetic Properties ◽  
Binding Energy ◽  
First Principles ◽  
Molecular Hydrogen ◽  
Density Functional ◽  
Hydrogen Molecule ◽  
Cobalt Atom ◽  
Electronic Charge ◽  
Practical Applications ◽  
Electronic And Magnetic Properties

The study of graphene and its allotropes help to understand fundamental science and their role in the industry. The adsorption of transition metal adatom on mono-layer graphene can tune the geometrical, electronic, and magnetic properties of the material according to the requirement for the practical applications. In the present work, the geometrical stability, electronic and magnetic properties, and also the redistribution of electronic charge of single cobalt atom (Co) adsorbed graphene with reference to pure graphene have been investigated to develop a model system for the effective storage of hydrogen. The density functional theory (DFT) based first-principles calculations by incorporating van der Waals (VDW) interactions within DFT-D2 levels of approximation implemented in the quantum ESPRESSO package was used. The band structure and density of states of cobalt-adatom graphene show that the material is metallic and magnetic with a total magnetic moment of 1.55 μB. The change in the electronic distribution of Co-adatom graphene has been found favorable for adsorbing molecular hydrogen/s with greater strength. The increasing number of adsorbed molecular hydrogen/s (n=1 to 7) onto the substrate shows varying binding energy per hydrogen molecule, high enough at low concentration (n=1, 2, and 3), and then decreases slowly on increasing the value of n. The nature of adsorption and binding energy per hydrogen molecule (with a range of 0.116 - 0.731 eV/ H2) are found useful to meet a standard target for hydrogen storage in such materials.

Study on the effects of Ga-2N high co-doping and preferred orientation on the stability, bandgap and absorption spectrum of ZnO

2017 ◽  
Vol 31 (14) ◽  
pp. 1750107
Author(s):  
Qing-Yu Hou ◽  
Wen-Cai Li ◽  
Ling-Feng Qu ◽  
Chun-Wang Zhao
Keyword(s):  
Absorption Spectrum ◽  
Absorption Spectra ◽  
Theoretical Calculations ◽  
Co Doping ◽  
Unit Cells ◽  
Neighboring Site ◽  
Doped Zno ◽  
The Stability ◽  
Formation Energies ◽  
Co Doped

Currently, the stability and visible light properties of Ga-2N co-doped ZnO systems have been studied extensively by experimental analysis and theoretical calculations. However, previous theoretical calculations arbitrarily assigned Ga- and 2N-doped sites in ZnO. In addition, the most stable and possible doping orientations of doped systems have not been fully and systematically considered. Therefore, in this paper, the electron structure and absorption spectra of the unit cells of doped and pure systems were calculated by first-principles plane-wave ultrasoft pseudopotential with the GGA[Formula: see text]U method. Calculations were performed for pure ZnO, Ga-2N supercells heavily co-doped with Zn[Formula: see text]Ga[Formula: see text]O[Formula: see text]N[Formula: see text] ([Formula: see text], [Formula: see text]) under different co-doping orientations and conditions, and the Zn[Formula: see text]GaN2O[Formula: see text] interstitial model. The results indicated that under different orientations and constant Ga-2N co-doping concentrations, the systems co-doped with Ga-N atoms vertically oriented to the [Formula: see text]-axis and with another N atom located in the nearest-neighboring site exhibited higher stability over the others, thus lowering formation energy and facilitating doping. Moreover, Ga-interstitial- and 2N-co-doped ZnO systems easily formed chemical compounds. Increasing co-doping concentration while the co-doping method remained constant decreased doped system volume and lowered formation energies. Meantime, co-doped systems were more stable and doping was facilitated. The bandgap was also narrower and red shifting of the absorption spectrum was more significant. These results agreed with previously reported experimental results. In addition, the absorption spectra of Ga-interstitial- and 2N-co-doped ZnO both blue shifted in the UV region compared with that of the pure ZnO system.

DEFECT FORMATION AND MAGNETIC PROPERTIES OF Co-DOPED ZnO NANOWIRES

NANO ◽  
2013 ◽  
Vol 08 (02) ◽  
pp. 1350021 ◽  
Author(s):  
LI BIN SHI ◽  
GUO QUAN QI ◽  
YING FEI
Keyword(s):  
Magnetic Properties ◽  
Density Functional ◽  
Defect Formation ◽  
Density Functional Method ◽  
Zno Nanowires ◽  
Generalized Gradient ◽  
Surface Sites ◽  
Doped Zno ◽  
Formation Energies ◽  
Co Doped

The defect formation energies and magnetic properties in Co -doped ZnO nanowires (NWs) are studied using the first-principle density functional method within the generalized gradient approximation (GGA) and GGA + U schemes. It is found that Co impurity has lower formation energies in the surface sites, indicating that Co impurity occupies preferably surface sites of NWs. Ferromagnetic (FM) and antiferromagnetic (AFM) coupling are investigated by GGA and GGA + U methods. The results show that the AFM coupling in energy is lower than the FM coupling, which indicates that AFM coupling is more stable. The magnetic properties can be mediated by the vacancies [ VO(B) and VZn(B) ] and interstitials [ IZn(oct) ]. The stability of the FM and AFM can be explained by the Co 3d energy level coupling.

Effect of Co-Doping on Electronic and Magnetic Properties in Ti2NiAl Heusler Alloy

2012 ◽  
Vol 602-604 ◽  
pp. 575-578
Author(s):  
Bo Wu ◽  
Xiu De Yang ◽  
Song Zhang
Keyword(s):  
Heusler Alloy ◽  
Density Functional ◽  
Magnetic Moments ◽  
High Energy ◽  
Type Structure ◽  
Local Spin Density Approximation ◽  
Lattice Constants ◽  
Co Doping ◽  
The Density Functional Theory ◽  
Co Doped

By using local spin density approximation (LSDA) scheme within the density functional theory (DFT), the structure, magnetism and electronic properties of Co-doped Heusler alloy Ti2NiAl with Hg2CuTi- and Cu2MnAl-type structure are comprehensively investigated. The results revealed that whole of the doped alloys with Hg2CuTi-type structure are ground configurations and half-metallic. With the increase of Co-doped concentration, the lattice constants and total magnetic moments in per unit are changed linearly, and the discrepancies of total energy between Hg2CuTi- and Cu2MnAl structure are also enhanced. Analysis on density of states (DOS) revealed that the Fermi level should gradually move to high-energy orientation with increasing Co content due to stronger hybridization of d-electronic atoms.

scholarly journals Large Piezoelectric Response and Ferroelectricity in Li and V/Nb/Ta co-doped w-AlN

2020 ◽  
Author(s):  
Mohammad Noor-A-Alam ◽  
Oskar Olszewski ◽  
Humberto Campanella ◽  
Michael Nolan
Keyword(s):  
Acoustic Wave ◽  
Density Functional ◽  
Electromechanical Coupling ◽  
Piezoelectric Materials ◽  
Electric Polarization ◽  
Piezoelectric Response ◽  
Co Doping ◽  
Piezoelectric Strain ◽  
Co Doped ◽  
Piezoelectric Strain Constant

<div>Based on density functional theory, we show that Li and</div><div>X (X=V, Nb and Ta) co-doping in 1Li:1X ratio broadens the</div><div>compositional freedom for significant piezoelectric enhancement in w-AlN, promising them to be good alternatives of expensive Sc. Interestingly, these co-doped w-AlN also show quite large spontaneous electric polarization about 0.80 C/m2 with the possibility of ferroelectric polarization switching, opening new possibilities in wurtzite nitrides. Increase in piezoelectric stress constant (e33) with decrease in elastic constant ( C33 ) results enhancement in piezoelectric strain constant ( d33 ), which is desired for improving the performance of resonators for high frequency RF signals. Also, these co-doped w-AlN are potential lead-free piezoelectric materials for energy harvesting and sensors as they improve the longitudinal electromechanical coupling constant (K^2 33), transverse piezoelectric strain constant (d31), and figure of merit for power generation. However, the enhancement in K^2 33 is not as pronounced as that in d33, because co-doping increases the dielectric constant. The longitudinal acoustic wave velocity (7.09 km/s) of Li0.1875Ta0.1875Al0.625N is quite comparable with that of commercially used piezoelectric LiNbO3 or LiTaO3 in special cuts (about 5~7 km/s) despite the fact that the acoustic wave velocities drop with co-doping or Sc concentration.</div>

First-principle study of SO2 adsorption on Fe/Co-doped vacancy defected single-walled (8, 0) carbon nanotubes in sensor applications

2019 ◽  
Vol 18 (05) ◽  
pp. 1950025 ◽  
Author(s):  
Meng Zhang ◽  
Guoqing Li ◽  
Xiaomin Lu ◽  
Qianru Zhang ◽  
Wei Li
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional ◽  
Energy Gap ◽  
Single Vacancy ◽  
Functional Theory ◽  
Sensor Applications ◽  
Co Doping ◽  
So2 Adsorption ◽  
Before And After ◽  
Co Doped

To explore the excellent sensor for detecting the pollution gas [Formula: see text], the adsorptions of [Formula: see text] molecule on the surfaces of Fe/Co-doped carbon nanotubes (CNTs) and single vacancy defected (8, 0) CNTs were investigated by using density functional theory (DFT). In addition, the adsorption energies, geometries, energy gaps and electronic structures were analyzed. The results showed that Fe/Co-doping and single-vacancy-defected can improve the adsorption and sensitiveness of CNTs toward [Formula: see text]. Considering the changes of energy gap before and after the [Formula: see text] molecule adsorbed on each modified CNTs and its adsorption strength, Fe-doped CNTs (Fe-CNTs) and Co-doped site-2 single-vacancy-defected CNTs performed better for detecting [Formula: see text] molecule. With the decreasing number of electrons of the doped atom (Fe, Co, Ni), the adsorption became more stable. The results of this paper are profound and meaningful for designing [Formula: see text] sensing devices.

Band-gap tuning of graphene by Be doping and Be, B co-doping: a DFT study

RSC Advances ◽  
2015 ◽  
Vol 5 (69) ◽  
pp. 55762-55773 ◽  
Author(s):  
Saif Ullah ◽  
Akhtar Hussain ◽  
WaqarAdil Syed ◽  
Muhammad Adnan Saqlain ◽  
Idrees Ahmad ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Co Doping ◽  
Structural And Electronic Properties ◽  
Doped Graphene ◽  
Band Gap Tuning ◽  
Co Doped

First-principles density functional theory (DFT) calculations were carried out to investigate the structural and electronic properties of beryllium (Be) doped and, Be with boron (B) co-doped graphene systems.

Effect of Co-Doping Cation on Phase Stability of Zirconia Bioceramics in Hot Water

2007 ◽  
Vol 26-28 ◽  
pp. 773-776
Author(s):  
S. Yuhara ◽  
Yorinobu Takigawa ◽  
Tokuteru Uesugi ◽  
Kenji Higashi
Keyword(s):  
Binding Energy ◽  
Oxygen Vacancy ◽  
Phase Stability ◽  
Vacancy Concentration ◽  
Hot Water ◽  
Oxygen Vacancy Concentration ◽  
Zirconia Ceramics ◽  
Axis Ratio ◽  
Co Doping ◽  
Co Doped

Phase stability of cation co-doped zirconia ceramics is examined. As the result, in contrast to the result in small amount of single cation doped zirconia, phase stability of co-doped zirconia ceramics can not be simply explained from ionic radius and valency of dopant or from the change in axis ratio. We focus on oxygen vacancy concentration and binding energy between oxygen vacancy and doped cation. By estimating phase stability from these factors, it is found that concentration of oxygen vacancy and the binding energy between the dopant and the oxygen vacancy are important factors for understanding the phase stability of zirconia ceramics.

scholarly journals Strong Valence Electrons Dependent and Logical Relations of Elemental Impurities in 2D Binary Semiconductor: a Case of GeP3 Monolayer from Ab Initio Studies

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Suihao Zhang ◽  
Rui Li ◽  
Xiaonan Fu ◽  
Yu Zhao ◽  
Chunyao Niu ◽  
...  
Keyword(s):  
Density Functional ◽  
Logical Relation ◽  
Comprehensive Understanding ◽  
Electron Hole ◽  
Functional Theory ◽  
Group Iii ◽  
Co Doping ◽  
Elemental Impurities ◽  
Valence Electrons ◽  
Co Doped

Abstract Using first-principle calculations within density functional theory, we investigate the electronic property and stability of substitutionally doped 2D GeP3 monolayer with dopants from group III to VI. The conducting properties are found to be dramatically modified by both the doping sites and the number of valence electrons of dopants. Specifically, substitution on Ge site exhibits metal-semiconductor oscillations as a function of the number of valence electrons of dopants, while such oscillations are totally reversed when substitution on P site. Moreover, we also study the case of co-doping in GeP3, showing that co-doping can produce a logical “AND” phenomenon, that is, the conducting properties of co-doped GeP3 can be deduced via a simple logical relation according to the results of single doping. Finally, we investigate the formation energy of dopants and find that the electron-hole and hole-hole co-doped systems are much more energetically favorable due to the Coulomb attraction. Our findings not only present a comprehensive understanding of 2D doping phenomenon, but also propose an intriguing route to tune the electronic properties of 2D binary semiconductors.

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