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- 1. J.Am.Chem.Soc. 130, 48 (2008) , ACS , “Enhanced Ferromagnetism and Tunable Saturation Magnetization of Mn/C Codoped GaN Nanostructures Synthesized by Carbothermal Nitridation”, Zeyan Wang, Baibiao Huang, Lin Yu, Ying Dai, Peng Wang, Xiaoyan Qin, Xiaoyang Zhang, Jiyong Wei, Jie Zhan, Xiangyang Jing, Haixia Liu, and Myung-Hwan WhangboMn/C-codoped GaN nanostructures were synthesized by carbothermal nitridation with active charcoal as the carbon source. Nanostructures such as zigzag nanowires and nanoscrews were observed by varying the reaction time and the C/Ga molar ratio of the starting material used for the synthesis. The structures and morphologies of the as-grown samples were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy measurements. The doping of both Mn and C in the GaN matrix was confirmed by X-ray photoelectron spectroscopy measurements, and the ferromagnetic properties of Mn/C-codoped GaN samples were confirmed by room-temperature magnetization measurements. The saturation magnetization of Mn/C-codoped GaN increases steadily with increasing C/Ga molar ratio of the starting material at a rate of ~0.023 emu/g per C/Ga molar ratio, and the ferromagnetism of Mn/C-codoped GaN can be stronger than that of Mn-doped GaN by a factor of ~40. A plausible growth mechanism was proposed, and the role of carbon codoping in tuning the morphology and ferromagnetic property was discussed. Our work suggests that carbon doping in the GaN matrix favors the N sites over the Ga sites, Mn/C-codoping in the GaN matrix is energetically favorable, and the C-codoping strongly enhances the preference of the FM coupling to the AFM coupling between the two doped Mn sites. These suggestions were probed on the basis of first-principles density functional theory electronic structure calculations for a number of model doped structures constructed with a 32-atom 2 × 2 × 2 supercell. (Read more)
- 2. Phys. Rev. B 75, 115201 (2007) , “Atomistic modeling of the (a+c)-mixed dislocation core in wurtzite GaN”, I. Belabbas, A. Béré, J. Chen, S. Petit, M. Akli Belkhir, P. Ruterana, and G. NouetAn atomistic simulation of the threading (a+c)-mixed dislocation core in wurtzite GaN has been carried out. Starting from models generated in the framework of continuum elasticity theory, two core configurations are obtained independently by using an empirical potential and a... (Read more)
- 3. Phys. Rev. B 75, 085204 (2007) , “Internal structure of the neutral donor-bound exciton complex in cubic zinc-blende and wurtzite semiconductors”, Bernard Gil, Pierre Bigenwald, Mathieu Leroux, Plamen P. Paskov, and Bo MonemarWe calculate the fine structure splitting of the near band edge donor-bound excitons in major cubic semiconductors using an approach inspired by an earlier one that consists in replacing the Morse potential by a Kratzer one, in order to account for the repulsion between the donor and the hole. A... (Read more)
- 4. Phys. Rev. B 75, 075312 (2007) , “Ferromagnetic to ferrimagnetic crossover in Cr-doped GaN nanohole arrays”, Q. Wang, Q. Sun, P. Jena, and Y. KawazoeUsing spin-polarized density-functional theory with exchange and correlation potential, approximated by both the generalized gradient approximation (GGA) and the GGA+U methods, we show that the coupling between a pair of Cr atoms substituted in GaN nanoholes is ferromagnetic. The interaction between... (Read more)
- 5. Phys. Rev. B 75, 035322 (2007) , “Ab initio study of electronic and magnetic properties of the C-codoped Ga1−xMnxN (100) surface”, Q. Wang, Q. Sun, and P. JenaFirst principles calculations based on gradient corrected density functional theory have been carried out to study the magnetic coupling between Mn atoms in pure and carbon doped Ga1−xMnxN thin films. We show that the ground state of Mn-doped GaN (100) thin... (Read more)
- 6. J. Appl. Phys. 100, 123108 (2006) , “Density functional theory investigation of N interstitial migration in GaN”, R. R. Wixom and A. F. WrightUsing density-functional total energy calculations, we investigated N interstitial migration in GaN. Two migration paths were considered. The first path confines motion to a single c-plane of the lattice, while the second path involves movement both perpendicular and parallel to the... (Read more)
- 7. J. Appl. Phys. 99, 113506 (2006) , “Theoretical properties of the N vacancy in p-type GaN(Mg,H) at elevated temperatures”, S. M. Myers, A. F. Wright, M. Sanati, and S. K. EstreicherThe elevated-temperature properties of the N vacancy in Mg-doped, p-type GaN containing H were modeled using atomic-configuration energies and phonon densities of states obtained with density-functional theory. This study encompassed both equilibrium thermodynamics and the rates of diffusion... (Read more)
- 8. Phys. Rev. B 74, 245216 (2006) , “Influence of excited states of a deep substitutional dopant on majority-carrier concentration in semiconductors”, Hideharu MatsuuraThe density (NA) and energy level (EA) of an acceptor in a p-type wide-band-gap semiconductor (e.g., SiC, GaN, and diamond) are determined by a least-squares fit of the charge neutrality equation to the temperature dependence of the hole... (Read more)
- 9. Phys. Rev. B 74, 045202 (2006) , “Effects of cation d states on the structural and electronic properties of III-nitride and II-oxide wide-band-gap semiconductors”, Anderson Janotti, David Segev, and Chris G. Van de WalleUsing first-principles methods based on density functional theory within the local density approximation (LDA) we calculate the structural and electronic properties of wurtzite MgO, ZnO, and CdO, and discuss their similarities and dissimilarities with the corresponding Group-III nitrides AlN, GaN,... (Read more)
- 10. Phys. Rev. B 68, 085202 (2003) , “Physics and chemistry of hydrogen in the vacancies of semiconductors”, Bernadett Szûcs, Adam Gali, Zoltán Hajnal, Peter Deák, and Chris G. Van de WalleHydrogen is well known to cause electrical passivation of lattice vacancies in semiconductors. This effect follows from the chemical passivation of the dangling bonds. Recently it was found that H in the carbon vacancy of SiC forms a three-center bond with two silicon neighbors in the vacancy, and... (Read more)
- 11. Phys. Rev. B 63, 165204 (2001) , “g values of effective mass donors in AlxGa1-xN alloys”, M. W. Bayerl, M. S. Brandt, T. Graf, O. Ambacher, J. A. Majewski, M. Stutzmann, D. J. As, K. LischkaElectron spin resonance experiments were performed on Si-doped wurtzite and zinc-blende GaN and Si-doped wurtzite AlxGa1-xN alloys with x=0.15, 0.32, 0.52, 0.75, and 1. For zinc-blende GaN, an isotropic g factor of 1.9475 is found. The g tensors of the silicon effective mass... (Read more)
- 12. Phys. Rev. B 62, 12923-12926 (2000) , “Electron paramagnetic resonance of Cu(d9) in GaN”, C. Bozdog, K. H. Chow, G. D. Watkins, H. Sunakawa, N. Kuroda, A. UsuiElectron paramagnetic resonance of Cu2+(d9) has been detected optically in the visible and near-infrared luminescence of wurtzite GaN. Its effective S=1/2 spin Hamiltonian parameters are g‖=±0.20(5), g⊥=+1.549(1), and... (Read more)
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