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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, 144404 (2007) , “Ferromagnetism in Fe-doped ZnO nanocrystals: Experiment and theory”, Debjani Karmakar, S. K. Mandal, R. M. Kadam, P. L. Paulose, A. K. Rajarajan, T. K. Nath, A. K. Das, I. Dasgupta, and G. P. DasFe-doped ZnO nanocrystals are successfully synthesized and structurally characterized by using x-ray diffraction and transmission electron microscopy. Magnetization measurements on the same system reveal a ferromagnetic to paramagnetic transition temperature above 450 K with a low-temperature... (Read more)
- 3. J. Appl. Phys. 100, 034309 (2006) , “Critical size for defects in nanostructured materials”, Jagdish NarayanThis paper addresses some of the fundamental issues and critical advantages in reducing the grain size/feature size to the nanoscale regime. We find that as the grain size or feature size is reduced, there is a critical size below which the defect content can be reduced virtually to zero. This... (Read more)
- 4. J. Appl. Phys. 99, 011101 (2006) , “Degradation of hexagonal silicon-carbide-based bipolar devices”, M. Skowronski and S. HaOnly a few years ago, an account of degradation of silicon carbide high-voltage p-i-n diodes was presented at the European Conference on Silicon Carbide and Related Compounds (Kloster Banz, Germany, 2000). This report was followed by the intense effort of multiple groups... (Read more)
- 5. J. Appl. Phys. 91, 8919-8941 (2002) , “Transient Enhanced Diffusion of Boron in Si”, S. C. Jain, W. Schoenmaker, R. Lindsay, P. A. Stolk, S. Decoutere, M. Willander, H. E. Maes.On annealing a boron implanted Si sample at ~800 °C, boron in the tail of the implanted profile diffuses very fast, faster than the normal thermal diffusion by a factor 100 or more. After annealing for a sufficiently long time, the enhanced diffusion saturates. The enhanced diffusion is... (Read more)
- 6. J. Appl. Phys. 59, 3255-3266 (1986) , “Thermodynamic and Kinetic Considerations on the Equilibrium Shape for Thermally Induced Microdefects in Czochralski Silicon”, W. A. Tiller, S. Hahn, F. A. Ponce.Using thermodynamic and kinetic considerations, we explain the quasiequilibrium, morphological, and structural characteristics of thermally induced oxide precipitates in Czochralski silicon. A model based upon the formation of Frenkel defects at the silicon/silica interface is used to explain the... (Read more)
- 7. Phys. Rev. B 34, 3610-3619 (1986) , “Dipolar interactions between dangling bonds at the (111) Si-SiO2 interface”, K. L. Brower, T. J. HeadleyIn this paper a computational model is developed which allows one to calculate the contribution to the Zeeman linewidth arising from magnetic dipole-dipole interactions between unpaired electrons in the dilute limit, which in our specific application correspond to dangling bonds (Pb... (Read more)
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