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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, 035309 (2007) , “Role of hydrogen in hydrogen-induced layer exfoliation of germanium”, J. M. Zahler, A. Fontcuberta i Morral, M. J. Griggs, Harry A. Atwater, and Y. J. ChabalThe role of hydrogen in the exfoliation of Ge is studied using cross-sectional transmission electron microscopy, atomic force microscopy, and multiple-internal transmission mode Fourier-transform infrared absorption spectroscopy and compared with the mechanism in silicon. A qualitative model for the... (Read more)
- 3. J. Appl. Phys. 100, 094108 (2006) , “The effect of interfacial layer properties on the performance of Hf-based gate stack devices”, G. Bersuker, C. S. Park, J. Barnett, P. S. Lysaght, P. D. Kirsch, C. D. Young, R. Choi, B. H. Lee, B. Foran, K. van Benthem, S. J. Pennycook, P. M. Lenahan, and J. T. RyanThe influence of Hf-based dielectrics on the underlying SiO2 interfacial layer (IL) in high-k gate stacks is investigated. An increase in the IL dielectric constant, which correlates to an increase of the positive fixed charge density in the IL, is found to depend on the starting,... (Read more)
- 4. Phys. Rev. B 67, 195338 (2003) , “Layer-resolved kinetics of Si oxidation investigated using the reflectance difference oscillation method”, T. Yasuda, N. Kumagai, M. Nishizawa, S. Yamasaki, H. Oheda, and K. YamabeDry oxidation kinetics of the Si(001) surface has been investigated using reflectance difference oscillation to resolve atomic-scale phenomena. The activation energy for oxidation has been found to increase as the oxide-Si interface moves in the depth direction, reaching the value for bulk... (Read more)
- 5. Phys. Rev. Lett. 90, 155901 (2003) , “Fluorine in Silicon: Diffusion, Trapping, and Precipitation”, X. D. Pi, C. P. Burrows, P. G. ColemanThe effect of vacancies on the behavior of F in crystalline Si has been elucidated experimentally for the first time. With positron annihilation spectroscopy and secondary ion mass spectroscopy, we find that F retards recombination between vacancies (V) and interstitials (I) because V and I trap F to form complexes. F diffuses in the V-rich region via a vacancy mechanism with an activation energy of 2.12±0.08 eV. After a long annealing time at 700ºC, F precipitates have been observed by cross-section transmission electron microscopy which are developed from the V-type defects around the implantation range and the I-type defects at the end of range. (Read more)
- 6. Mater. Sci. Eng. R 33, 135-207 (2001) , “Comprehensive characterization of hydride VPE grown GaN layers and templates”, H. MorkoçGaN community has recently recognized that it is imperative that the extended, and point defects in GaN and related materials, and the mechanisms for their formation are understood. This is a first and an important step, which must be followed by defect reduction before full implementation of this... (Read more)
- 7. J. Phys. Chem. Solids 31, 1381 (1970) , “The Annealing of the EPR-Signal Produced in Silicon by Plastic Deformation”, F. D. Wohler and H. AlexanderW. SanderIn silicon an EPR signal is produced by plastic deformation. The annealing behavior of this signal has been investigated, and the dislocation density and structure has been studied by the etch pit technique and by electron microscopy. The EPR-signal anneals in one stage with an activation energy of... (Read more)
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