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- 1. 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
- 2. Phys. Rev. B 75, 115206 (2007) , “Local-density-functional calculations of the vacancy-oxygen center in Ge”, A. Carvalho, R. Jones, J. Coutinho, V. J. B. Torres, S. Öberg, J. M. Campanera Alsina, M. Shaw, and P. R. BriddonWe carry out a comprehensive density-functional study of the vacancy-oxygen (VO) center in germanium using large H-terminated Ge clusters. The importance of a nonlinear core correction to account for the involvement of the 3d electrons in Ge-O bonds is discussed. We calculate the electrical... (Read more)
- 3. Appl. Phys. Lett. 89, 142914 (2006) , “Defect passivation in HfO2 gate oxide by fluorine”, K. Tse and J. RobertsonThe authors have calculated that fluorine substituting for oxygen gives no gap states in HfO2. This accounts for the good passivation of oxygen vacancies by F seen experimentally. Bonding arguments are used to account for why F may be the most effective passivant in ionic oxides such as... (Read more)
- 4. Appl. Phys. Lett. 89, 082908 (2006) , “Negative oxygen vacancies in HfO2 as charge traps in high-k stacks”, J. L. Gavartin, D. Muñoz Ramo, A. L. Shluger, G. Bersuker, and B. H. LeeThe optical excitation and thermal ionization energies of oxygen vacancies in m-HfO2 are calculated using a non-local density functional theory with atomic basis sets and periodic supercell. The thermal ionization energies of negatively charged V and... (Read more)
- 5. Appl. Phys. Lett. 88, 253504 (2006) , “Single silicon vacancy-oxygen complex defect and variable retention time phenomenon in dynamic random access memories”, T. Umeda, K. Okonogi, K. Ohyu, S. Tsukada, K. Hamada, S. Fujieda, and Y. MochizukiThe variable retention time phenomenon has recently been highlighted as an important issue in dynamic random access memory (DRAM) technology. Based on electrically detected magnetic resonance and simulation studies, we suggest that a single Si vacancy-oxygen complex defect is responsible for this... (Read more)
- 6. Appl. Phys. Lett. 88, 201918 (2006) , “Diffusion of zinc vacancies and interstitials in zinc oxide”, Paul Erhart and Karsten AlbeThe self-diffusion coefficient of zinc in ZnO is derived as a function of the chemical potential and Fermi level from first-principles calculations. Density functional calculations in combination with the climbing image-nudged elastic band method are used in order to determine migration barriers for... (Read more)
- 7. Appl. Phys. Lett. 88, 182903 (2006) , “Effects of Al addition on the native defects in hafnia”, Q. Li, K. M. Koo, W. M. Lau, P. F. Lee, J. Y. Dai, Z. F. Hou, X. G. GongTwo occupied native defect bands are experimentally detected in pure HfO2. The density of states of band one in the middle of the band gap reduces drastically with the Al addition, while that of band two slightly above the valence-band maximum remains rather unaffected. We attribute the... (Read more)
- 8. Appl. Phys. Lett. 88, 162107 (2006) , “Physical origin of threshold voltage problems in polycrystalline silicon/HfO2 gate stacks”, Dae Yeon Kim, Joongoo Kang, and K. J. ChangBased on theoretical calculations, we find that at p+ polycrystalline silicon (poly-Si)/HfO2 gates, Si interstitials are easily migrated from the electrode, forming HfSi bonds with a charge transfer to the electrode, and the resulting interface dipole raises the Fermi level... (Read more)
- 9. J. Appl. Phys. 99, 044105 (2006) , “Passivation of oxygen vacancy states in HfO2 by nitrogen”, K. Xiong, J. Robertson, and S. J. ClarkNitrogen is known to reduce leakage currents and charge trapping in high-dielectric-constant gate oxides such as HfO2. We show that this occurs because nitrogen, substituting for oxygen atoms next to oxygen vacancy sites, repels the occupied gap states due to the neutral and positively... (Read more)
- 10. Phys. Rev. Lett. 96, 55501 (2006) , “Divacancy in 4H-SiC”, N. T. Son, P. Carlsson, J. ul Hassan, E. Janzén, T. Umeda, J. Isoya, A. Gali, M. Bockstedte, N. Morishita, T. Ohshima, H. ItohElectron paramagnetic resonance and ab initio supercell calculations suggest that the P6/P7 centers, which were previously assigned to the photoexcited triplet states of the carbon vacancy-antisite pairs in the double positive charge state, are related to the triplet ground... (Read more)
- 11. Appl. Phys. Lett. 87, 062105 (2005) , “Negative-U property of oxygen vacancy in cubic HfO2”, Y. P. Feng, A. T. L. Lim, M. F. LiOxygen vacancy in cubic HfO2 was investigated using first-principles calculation based on density functional theory and generalized gradient approximation. Five different charge states (V++, V+, V0, V, and... (Read more)
- 12. Appl. Phys. Lett. 86, 143507 (2005) , “First-principles studies of the intrinsic effect of nitrogen atoms on reduction in gate leakage current through Hf-based high-k dielectrics”, N. Umezawa, K. Shiraishi, T. Ohno, H. Watanabe, T. Chikyow, K. Torii, K. Yamabe, K. Yamada, H. Kitajima, T. ArikadoThe atomistic effects of N atoms on the leakage current through HfO2 high-k gate dielectrics have been studied from first-principles calculations within the framework of a generalized gradient approximation (GGA). It has been found that the intrinsic effects of N atoms drastically... (Read more)
- 13. J. Appl. Phys. 97, 053704 (2005) , “The role of nitrogen-related defects in high-k dielectric oxides: Density-functional studies”, J. L. Gavartin, A. L. Shluger, A. S. Foster, G. I. BersukerUsing ab initio density-functional total energy and molecular-dynamics simulations, we study the effects of various forms of nitrogen postdeposition anneal (PDA) on the electric properties of hafnia in the context of its application as a gate dielectric in field-effect transistors. We... (Read more)
- 14. Eur. Phys. J. Appl. Phys. 27, 13-19 (2004) , “Measurement of process-induced defects in Si sub-micron devices by combination of EDMR and TEM”, T. Umeda, A. Toda, Y. MochizukiProcess-induced defects are a serious issue for modern sub-micron Si LSIs. To characterize such defects, two different techniques are useful: electrically detected magnetic resonance (EDMR) and transmission electron microscope (TEM), which can detect small (point) and extended defects, respectively. We applied EDMR and TEM to the issue of defect-induced leakage currents in dynamic-random-access memory (DRAM) cells. For our DRAM samples (a 0.25- Îźm-rule series), although TEM showed no extended defects, EDMR successfully detected two types of point defects: V2+O x (Si divacancy-oxygen complexes) and larger Si vacancies (at least larger than V6). We confirmed that these defects are the source of DRAM leakage currents. The observed defects were formed by ion implantation processes, but were more thermally stable than those in bulk Si crystals. The origins of this enhanced stability are attributed to the presence of oxygen atoms and a strong mechanical strain in LSIs. To clarify the origin of the complicated strain in LSI structures, we can directly measure the local-strain distribution in DRAM samples by means of convergent-beam electron diffraction (CBED) using TEM, which provides us with a valuable hint for understanding the formation mechanism of process-induced defects. (Read more)
- 15. J. Appl. Phys. 94, 7105-7111 (2003) , “Electrically detected magnetic resonance of ion-implantation damage centers in silicon large-scale integrated circuits”, T. Umeda, Y. Mochizuki, K. Okonogi, K. HamadaWe used electrically detected magnetic resonance to study the microscopic structure of ion-implantation-induced point defects that remained in large-scale Si integrated circuits (Si LSIs). Two types of defects were detected in the source/drain (n+-type) region of... (Read more)
- 16. Phys. Rev. B 59, 12900 (1999) , “Electron-paramagnetic-resonance measurements on the divacancy defect center R4/W6 in diamond”, D. J. Twitchen, M. E. Newton, J. M. Baker, T. R. Anthony, W. F. BanholzerElectron-paramagnetic-resonance (EPR) studies in radiation damaged diamond enriched to 5% 13C have resulted in the identification of the nearest-neighbor divacancy center. It is the isotopic enrichment, and consequent observation of 13C hyperfine lines, that has permitted the... (Read more)
- 17. Phys. Rev. Lett. 83, 372 (1999) , “Hydrogen Electrochemistry and Stress-Induced Leakage Current in Silica”, Peter E. Blöchl and James H. StathisHydrogen-related defects in oxygen-deficient silica, representing the material of a thermal gate oxide, are analyzed using first-principles calculations. Energetics and charge-state levels of oxygen vacancies, hydrogen, and their complexes in the silica framework are mapped out. The neutral hydrogen... (Read more)
- 18. Phys. Rev. Lett. 79, 1507 (1997) , “Identification of the Silicon Vacancy Containing a Single Hydrogen Atom by EPR”, B. Bech Nielsen, P. Johannesen, P. Stallinga, K. Bonde Nielsen
- 19. Proc. symp. on the degradation od electronic devices due to device operation as well as crystalline and process-induced defects 94-1, 221-234 (1994) , ECS (ISBN:1-56677-037-8) , “Spin dependent recombination in Si p-n junctions”, B. K. Meyer , P. Christmann , W. Stadler, H. Overhof, J.-M. Spaeth, S. Greulich-Weber, B. Stich
- 20. Phys. Rev. B 35, 1582 (1987) , “Electronic and Atomic Structure of the Boron-Vacancy Complex in Silicon”, M. Sprenger, R. van Kemp, E. G. Sieverts, and C. A. J. AmmerlaanIn electron-irradiated boron-doped silicon the electron paramagnetic resonance spectrum Si-G10 has been studied. Earlier this spectrum had tentatively been identified with a boron-vacancy complex in a next-nearest-neighbor configuration. With electron-nuclear double resonance the hyperfine and... (Read more)
- 21. Phys. Rev. B 13, 2511 (1976) , “EPR of a Trapped Vacancy in Boron-Doped Silicon”, G. D. Watkins.An S=1/2 EPR spectrum, labeled Si-G10, is tentatively identified as a lattice vacancy trapped by substitutional boron in silicon. It is produced in boron-doped vacuum floating-zone silicon by 1.5-MeV-electron irradiation at 20.4 K followed by an anneal at ? 180 K, where the isolated vacancy... (Read more)
- 22. Z. Physik B 23, 171-181 (1976) , “Intrinsic Defects in Electron Irradiated Zinc Oxide”, B. Schallenberge, A. Hausmann
- 23. Lattice Defects in Semiconductors 23, 1-22 (1975) , Institute of Physics, London , “EPR Studies of the Lattice Vacancy and Low-Temperature Damage Processes in Silocon”, G. D. Watkins.EPR studies of silicon irradiated at 20.4 K and 4.2 K by 1.5 MeV and 46 MeV electrons are described. In 46 MeV irradiations the dominant defects formed appear to be divavancies and other multiple defect aggregates which liberate vacancies throughout the anneal to room temperature as they reorder, recombine, etc. For 1.5 MeV irradiations group III atoms play a vital role in p- and n-type materials in trapping interstitials and stabilizing damage. Carbon and oxygen are not effective interstitial traps at these temperatures. Evidence of limited vacancy migration during irradiation is also cited. Two distinct excited configurations of vacancy-oxygen pairs are identified as precursors to A-centre formation in n-type silicon. The kinetics for their conversion to A-centres depends strongly upon the Fermi level as does the isolated vacancy migration energy whhich is measured to be 0.18 Âą 0.02 eV for the Vďź charge state. The vacancy has four charge states, Vďź, V0, Vďź and Vďź. Kinetics for hole release from Vďź reveals an activation barrier of 0.057 eV. The concentration of Vďź at 20.4 K in boron-doped material indicates the corresponding donor level even closer to the band edge, approximately EV ďź 0.039 eV. Jahn-Teller energies for V0, Vďź, and Vďź are estimated from stress-alignment studies and confirmed to be large. Kinetics studies for reorientation from one Jahn-Teller distortion to another are also described for each charge state.
- 24. Phys. Rev. B 9, 4351-4361 (1974) , “EPR study of defects in neutron-irradiated silicon: Quenched-in alignment under <110>-uniaxial stress”, Young-Hoon Lee and James W. CorbettThe stress effect in an EPR study is first treated rigorously in terms of the piezospectroscopic tensor, taking account of the local symmetry of a defect. It is found that the degree of alignment (n?/n?) provides incisive information on the structure of a defect; in general, a... (Read more)
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