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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 77, 195204 (2008) , “Identification of antisite carbon split-interstitial defects in 4H-SiC”, J. W. Steeds, W. SullivanA rich variety of optical centers with high energy local vibrational modes has been found in electron-irradiated 4H-SiC in both the as-irradiated and annealed states. These energies have been measured and the annealing dependence of the optical centers has been investigated by low-temperature... (Read more)
- 3. Phys. Rev. B 77, 195203 (2008) , “Creation and identification of the two spin states of dicarbon antisite defects in 4H-SiC”, J. W. Steeds, W. Sullivan, S. A. Furkert, G. A. Evans, P. J. WellmannThis paper deals with the positive identification by low-temperature photoluminescence microspectroscopy of the two spin states of the dicarbon antisites in 4H-SiC. The defects are created by high-dose electron irradiation at room temperature or by subsequent exposure to intense 325 nm radiation at... (Read more)
- 4. Phys. Rev. B 77, 085120 (2008) , “Identification of the carbon antisite in SiC: EPR of 13C enriched crystals”, Pavel G. Baranov, Ivan V. Ilyin, Alexandra A. Soltamova, and Eugene N. MokhovAn electron paramagnetic resonance spectrum with axial symmetry along c axis, spin S=1/2 and strong hyperfine interaction with one carbon atom has been observed in neutron-irradiated and annealed 6H-SiC, 13C isotope enriched. The 13C concentration was... (Read more)
- 5. phys. stat. sol. (b) 245, 1298-1314 (2008) , “EPR identification of intrinsic defects in SiC”, J. Isoya, T. Umeda, N. Mizuochi, N. T. Son, E. Janzen, T. OhshimaThe structure determination of intrinsic defects in 4H-SiC, 6H-SiC, and 3C-SiC by means of EPR is based on measuring the angular dependence of the 29Si/13C hyperfine (HF) satellite lines, from which spin densities, sp-hybrid ratio, and p-orbital direction can be determined over... (Read more)Si SiC diamond| EPR Theory electron-irradiation thermal-meas./anneal-exp.| +1 -1 0(neutral) 1.0eV~ 13C 29Si C1h C3v Carbon Csi D2d EI5/6 HEI1 HEI9/10 P6/7 Silicon T1 Td Tv2a V1/2/3 Vc Vsi antisite dangling-bond mono(=1) motional-effect n-type p-type pair(=2) quartet semi-insulating spin-relaxation triplet vacancy .inp files: SiC/Baranov/Baranov_g.inp SiC/EI5_C1h/5.inp SiC/EI5_C3v/5.inp SiC/EI6_RT/6.inp SiC/HEI10/HEI10a.inp SiC/HEI10/HEI10b.inp SiC/HEI1_C1h/1.inp SiC/HEI9/HEI9a.inp SiC/HEI9/HEI9b.inp SiC/SI5_C1h/4.inp SiC/Ky2/Ky2.inp SiC/Tv2a/Main.INP SiC/Vsi-_II_4H/Main.INP SiC/Vsi-_II_6H/Main.INP SiC/Vsi-_I_4H/Main.INP SiC/Vsi-_I_6H/Main.INP | last update: Takahide Umeda
- 6. Appl. Phys. Lett. 91, 133507 (2007) , “Identification of atomic-scale defect structure involved in the negative bias temperature instability in plasma-nitrided devices”, J. P. Campbell, P. M. Lenahan, A. T. Krishnan, and S. KrishnanWe utilize a very sensitive electron spin resonance technique called spin-dependent tunneling to identify defect centers involved in the negative bias temperature instability in plasma-nitrided p-channel metal-oxide-silicon field-effect transistors. The defect's 29Si hyperfine... (Read more)
- 7. Appl. Phys. Lett. 90, 123502 (2007) , “Observation of negative bias stressing interface trapping centers in metal gate hafnium oxide field effect transistors using spin dependent recombination”,The authors combine metal oxide semiconductor (MOS) gated diode measurements and very sensitive electrically detected electron spin resonance measurements to detect and identify negative bias temperature instability (NBTI) generated defect centers in fully processed HfO2 pMOS field effect... (Read more)
- 8. J. Appl. Phys. 102, 013530 (2007) , “Fluorine-vacancy complexes in Si-SiGe-Si structures”, D. A. Abdulmalik, P. G. Coleman, H. A. W. El Mubarek, and P. AshburnFluorine-vacancy (FV) complexes have been directly observed in the Si0.94Ge0.06 layer in a Si-SiGe-Si structure, using variable-energy positron annihilation spectroscopy (VEPAS). These complexes are linked to the significant reduction of boron diffusion in the SiGe layer via... (Read more)
- 9. J. Appl. Phys. 101, 013703 (2007) , “Electron spin resonance study of as-deposited and annealed (HfO2)x(SiO2)1−x high-κ dielectrics on Si”, B. B. Triplett, P. T. Chen, Y. Nishi, P. H. Kasai, J. J. Chambers, and L. ColomboElectron spin resonance measurements on 4 and 40 nm thick (HfO2)0.6(SiO2)0.4 and (HfO2)0.4(SiO2)0.6 high-κ films on (100)Si wafers detected Pb0 and Pb1... (Read more)
- 10. Phys. Rev. B 75, 245202 (2007) , “Identification of positively charged carbon antisite-vacancy pairs in 4H-SiC”, T. Umeda, J. Ishoya, T. Ohshima, N. Morishita, H. Itoh, and A. GaliAn antisite-vacancy pair and a monovacancy are a set of fundamental stable and/or metastable defects in compound semiconductors. Theory predicted that carbon antisite-vacancy pairs would be much more stable in p-type SiC than silicon vacancies and that they would be a common defect. However,... (Read more)
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