| 1. |
- Cao, H. W., et al.
(författare)
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Electronic and magnetic properties of vanadium doped AlN nanosheet under in-plane biaxial strains
- 2014
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 73, s. 113-120
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations have been performed to investigate the electronic and magnetic properties of V-doped AlN nanosheet under in-plane biaxial strains. It is found that V atom favors to substitute for Al site with the lowest formation energy. The magnetic coupling of three different configurations are studied and configuration I is demonstrated to possess room temperature ferromagnetism. The stable ferromagnetic coupling is mediated by double exchange mechanism. In addition, the in-plane biaxial strains corresponding to tensile and compressive strains can affect and manipulate the magnetic interaction of V-doped AlN nanosheet in different ways. These results are conductive to design AlN based two dimensional diluted magnetic semiconductors.
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| 2. |
- Cao, H. W., et al.
(författare)
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First-principles study on electronic and magnetic properties of (Mn,Fe)-codoped ZnO
- 2014
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 352:1, s. 66-71
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Tidskriftsartikel (refereegranskat)abstract
- First-principle calculations have been performed to investigate the electronic and magnetic properties of (Mn,Fe)-codoped ZnO within the generalized gradient approximation (GGA) and GGA+U schemes. The formation energy of five different configurations is investigated and the ground state is demonstrated to be ferromagnetic ordering. By applying the U correction, the band gap energy of pure ZnO is close to the experimental values, while the ferromagnetic ordering of the ground state remains unchanged. The ferromagnetic stabilization is mediated by double exchange mechanism. In addition, defects corresponding to Zn-vacancy and O-vacancy cannot enhance the ferromagnetism obviously. These results indicate that (Mn,Fe)-codoped ZnO are promising magneto-electronic and spintronic materials. (C) 2013 Elsevier B.V. All rights reserved
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| 3. |
- Cao, H. W., et al.
(författare)
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Hybrid functional investigations of the crystal structure, band gap energy, and elastic coefficients of GaAs1-xBix solid solutions
- 2015
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Ingår i: Computational Materials Science. - : Elsevier BV. - 0927-0256. ; 105, s. 6-10
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Tidskriftsartikel (refereegranskat)abstract
- First-principles hybrid functional calculations have been performed to study the crystal structure, band gap energy, and elastic coefficients of GaAs1-xBix solid solutions. Three different structures in prototype wurtzite and orthorhombic symmetries are considered. Compared to O-16 and O-32 supercells, GaAs1-xBix alloys in W-16 structure are more stable with the lower formation energy for a given Bi concentration. The lattice constants of GaAs1-xBix solid solutions follow the Vegard's Law regardless of the three different structures. Although the band gap decreases with the increase of Bi concentration, the trends of the band gap energy in the W-16, O-16 and O-32 structures are nearly identical. The calculated elastic coefficients and bulk modulus display a discernible downward bowing and there exists a direct correlation between the elastic stiffness coefficients and strains. These results give a good understanding of the properties of GaAs1-xBix solid solutions.
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| 4. |
- Cao, H. W., et al.
(författare)
-
Magnetic properties in (Mn,Fe)-codoped ZnO nanowire
- 2013
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090. ; 548, s. 480-484
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Tidskriftsartikel (refereegranskat)abstract
- Using the first-principles density functional theory, we have studied the electronic structures and magnetic properties of Mn/Fe codoped ZnO nanowires systematically. The calculated results of formation energy indicate that the configuration of the lowest energy where Mn and Fe atoms form nearest neighbors on the outer cylindrical surface layer along the [0001] direction, will be determined. The magnetic coupling of 8 types of Mn/Fe codoped ZnO nanowires was investigated and ferromagnetic state was found in certain configurations. The mechanism is from the fierce hybridization between 3d of Mn and Fe with O 2p near the Fermi level. The relative energy difference for configuration VIII is 0.221 eV, which indicates that room temperature ferromagnetism could be obtained in such a system and Mn/Fe codoped ZnO nanowires are a promising nanoscale spintronic material. (C) 2013 Elsevier B. V. All rights reserved.
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| 5. |
- Cao, H. W., et al.
(författare)
-
Structural and electronic properties of wurtzite GaX (X = N, P, As, Sb, Bi) under in-plain biaxial strains
- 2014
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 67, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- Using first-principles density functional theory, we have investigated the structural and electronic properties of GaX (X N, P, As, Sb, Bi) systems under in-plain biaxial strains. All GaX systems transfer from the typical wurtzite to pseudographitic phases when the in-plane tensile strains are large enough. Our findings indicate that the elastic stiffness coefficients have a direct correlation with the strains. The variations of the band gap energy are diverse with respect to the compressive and tensile biaxial strains. For tensile biaxial strains, the band gap decreases substantially as the increasing of the strains. Upon compressive biaxial strains, the band gap initially increases, and then undergoes a decline. In addition, we find that there exists an indirect to direct band gap transition of GaP at certain in-plane biaxial strains. These results give a good understanding of strain-based GaX series heteroepitaxy thin films. (C) 2014 Elsevier Ltd. All rights reserved.
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| 6. |
- Ding, L., et al.
(författare)
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Bismuth alloying properties in GaAs nanowires
- 2013
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 205, s. 44-48
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations have been performed to investigate the structural, electronic and optical properties of bismuth alloying in GaAs nanowires. A typical model of Ga31As31 nanowires is introduced for its reasonable band gap. The band gap of GaAs1-xBix shrinks clearly with the increasing Bi concentration and the band edge shifts when spin-orbit coupling (SOC) is considered. The insertion of Bi atom leads to hybridization of Ga/As/Bi p states which contributes a lot around Fermi level. Scissor effect is involved. The optical properties are presented, including dielectric function, optical absorption spectra and reflectivity, which are also varied with the increasing of Bi concentrations.
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| 7. |
- Lu, P. F., et al.
(författare)
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A theoretical investigation on thermoelectric performance of ternary (Bi1-xSbx)(2)Te-3 compound
- 2013
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 48:14, s. 4999-5004
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure and thermoelectric properties of (Bi1-x Sb (x) )(2)Te-3 compound are investigated by using full-potential linearized augmented plane-wave method and semiclassical Boltzmann theory. The density of states and band structure are studied in detail. The transport coefficients are then calculated with the assumption of the constant relaxation time approximation. We investigated the thermoelectric properties at full range of Sb compositions from x = 0 to x = 1. By using the calculated thermoelectric properties and an averaged thermal conductivity, the figure of merit ZT is obtained. The theoretical investigations show a good agreement with the present experimental data.
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| 8. |
- Lu, P. F., et al.
(författare)
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Investigation on structural, electronic and magnetic propeties of Mn doped Ga12N12 clusters
- 2013
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 48:24, s. 8552-8558
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Tidskriftsartikel (refereegranskat)abstract
- The structural, electronic, and magnetic properties of Ga12N12 cluster doped with monodoped and bidoped Mn atoms have been investigated based on the density functional theory. Substitutional, exohedral, and endohedral configurations are considered. The substitutional doping is found to be most favorable for monodoped clusters, while the bidoped clusters prefer the exohedral isomers. For all the isomer, the magnetic moment is mainly derived from 3d orbitals of Mn atom. The exohedral and endohedral bidoped Ga12N12 clusters all favor antiferromagnetic state.
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| 9. |
- Lu, P. F., et al.
(författare)
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Strain induced composition profile in InGaN/GaN core-shell nanowires
- 2014
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098. ; 178, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical investigation on explanation of the composition profile in triangular and hexagonal cross-sections of InGaN/GaN core-shell nanowires is presented by combining the finite elements method (FEM) and method of moving asymptotes (MMA) in the framework of thermodynamics. Our models can account for strain effect on indium composition. In both models, the maximum indium content through segregation arises either at the side length or at the corner of the InGaN shell. The simulated results are found in good agreement with those of experimental data, thus providing a good guidance for the growth of high indium concentration of InGaN/GaN core-shell nanowires.
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| 10. |
- Lu, P. F., et al.
(författare)
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Structural properties and energetics of GaAs nanowires
- 2013
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Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - : Elsevier BV. - 1386-9477. ; 52, s. 34-39
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Tidskriftsartikel (refereegranskat)abstract
- Using the first-principles density functional theory, we have investigated the geometric structure and electronic properties of GaAs nanowires. Compared with bulk GaAs, wurtzite nanowires are found to be more stable over zinc-blende nanowires. A revised cohesive energy is provided based on the influence of different kinds of surface dangling bonds. Our calculation indicates that GaAs nanowires display bistability namely both zinc-blende and wurtzite nanowire will form around 90 A diameters. Furthermore, most GaAs nanowires are found to be semiconducting except for the zinc-blende nanowires. In zinc-blende nanowires it is mainly due to the twofold coordinated atoms associated with the surface state will decrease the band gap. Upon H passivation, these nanowires become semiconducting and the trend of the band gap decreases with the diameter increases.
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