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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. 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)
- 3. Phys. Rev. B 75, 035211 (2007) , “Self- and foreign-atom diffusion in semiconductor isotope heterostructures. II. Experimental results for silicon”, H. Bracht, H. H. Silvestri, I. D. Sharp, and E. E. HallerWe report the diffusion of boron, arsenic, and phosphorus in silicon isotope multilayer structures at temperatures between 850 °C and 1100 °C. The diffusion of all dopants and self-atoms at a given temperature is modeled with the same setting of all native-point-defect-related parameters.... (Read more)
- 4. Phys. Rev. Lett. 98, 265502 (2007) , “Monovacancy and Interstitial Migration in Ion-Implanted Silicon”, P. G. Coleman and C. P. BurrowsThe migration of monovacancies (V0) and self-interstitials (I) has been observed in ion-implanted low-doped float-zone silicon by variable-energy positron annihilation spectroscopy. V0 and I were created by the in situ implantation of ~20 keV... (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. Phys. Rev. B 74, 235209 (2006) , “Comparison of two methods for circumventing the Coulomb divergence in supercell calculations for charged point defects”, A. F. Wright and N. A. ModineDensity-functional-theory calculations were performed for the unrelaxed +2 Si vacancy and +2 self-interstitial utilizing periodic boundary conditions and two different methods—the uniform background charge method and the local moment counter charge method—for circumventing the divergence... (Read more)
- 7. Phys. Rev. B 74, 205208 (2006) , “Formation energies, binding energies, structure, and electronic transitions of Si divacancies studied by density functional calculations”, R. R. Wixom and A. F. WrightAtomic configurations, formation energies, electronic transition energies, and binding energies of the silicon divacancy in the +1, 0, −1, and −2 charge states were obtained from density functional theory calculations. The calculations were performed using the local density approximation... (Read more)
- 8. 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)
- 9. Phys. Rev. B 72, 235208 (2005) , “Spin multiplicity and charge state of a silicon vacancy (TV2a) in 4H-SiC determined by pulsed ENDOR”, N. Mizuochi, S. Yamasaki, H. Takizawa, N. Morishita, T. Ohshima, H. Itoh, T. Umeda, and J. IsoyaIn this paper, we unambiguously re-determine the spin multiplicity of TV2a by pulsed electron nucleus double resonance technique. The TV2a center is one of the most commonly observed defects in 4H-SiC, and its origin was... (Read more)
- 10. Phys. Rev. B 72, 045219 (2005) , “Fluorine in Si: Native-defect complexes and the supression of impurity diffusion”, Giorgia M. Lopez, Vincenzo Fiorentini, Giuliana Impellizzeri, Salvatore Mirabella, Enrico NapolitaniThe transient enhanced diffusion of acceptor impurities severely affects the realization of ultrahigh doping regions in miniaturized Si-based devices. Fluorine codoping has been found to suppress this transient diffusion, but the mechanism underlying this effect is not understood. It has been proposed that fluorine-impurity or fluorine–native-defect interactions may be responsible. Here we clarify this mechanism combining first-principles theoretical studies of fluorine in Si and purposely designed experiments on Si structures containing boron and fluorine. The central interaction mechanism is the preferential binding of fluorine to Si-vacancy dangling bonds and the consequent formation of vacancy-fluorine complexes. The latter effectively act as traps for the excess self-interstitials that would normally cause boron transient enhanced diffusion. Instead, fluorine-boron interactions are marginal and do not play any significant role. Our results are also consistent with other observations such as native-defect trapping and bubble formation. (Read more)
- 11. Appl. Phys. Lett. 85, 1538 (2004) , “Observation of fluorine-vacancy complexes in silicon”, P. J. Simpson, Z. Jenei, P. Asoka-Kumar, R. R. Robison, M. E. LawWe show direct evidence, obtained by positron annihilation spectroscopy, for the complexing of fluorine with vacancies in silicon. Both float zone and Czochralski silicon wafers were implanted with 30 keV fluorine ions to a fluence of 2×1014 ions/cm2, and studied in the... (Read more)
- 12. Appl. Phys. Lett. 84, 3406-3408 (2004) , “Structure of 6H silicon carbide/silicon dioxide interface trapping defects”, David J. Meyer, Nathaniel A. Bohna, and Patrick M. LenahanWe utilize spin-dependent recombination (SDR) to observe deep level trap defects at or very near the interface of 6H silicon carbide and the SiO2 gate dielectric in SiC metal-oxide-semiconductor field effect transistors. The SDR response is strongly correlated to SiC/SiO2... (Read more)
- 13. 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- μm-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)
- 14. Phys. Rev. Lett. 93, 245901 (2004) , “Ab Initio Calculations to Model Anomalous Fluorine Behavior”, Milan Diebel, Scott T. Dunhammplanted fluorine is observed to behave unusually in silicon, manifesting apparent uphill diffusion and reducing diffusion and enhancing activation of boron. In order to investigate fluorine behavior, we calculate the energy of fluorine defect structures in the framework of density functional theory. In addition to identifying the ground-state configuration and diffusion migration barrier of a single fluorine atom in silicon, a set of energetically favorable fluorine defect structures were found (FnVm). The decoration of vacancies and dangling silicon bonds by fluorine suggests that fluorine accumulates in vacancy-rich regions, which explains the fluorine redistribution behavior reported experimentally. (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. 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)
- 17. phys. stat. sol. (b) 210, 13 (1999) , “Neutral Vacancies in Group-IV Semiconductors”, A. Zywietz, J. Furthmüller, F. BechstedtAb initio plane-wave-supercell calculations are performed for the neutral monovacancies in silicon, silicon carbide and diamond using ultrasoft non-normconserving Vanderbilt pseudopotentials. We study the structure, the energetics and the single-particle energy spectrum. The local symmetry, the... (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. 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)
- 20. 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 ± 0.02 eV for the Vï¼ charge state. The vacancy has four charge states, V+, V0, Vï¼ and Vï¼. Kinetics for hole release from V+ reveals an activation barrier of 0.057 eV. The concentration of V+ at 20.4 K in boron-doped material indicates the corresponding donor level even closer to the band edge, approximately EV + 0.039 eV. Jahn-Teller energies for V0, V+, and Vï¼ 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.
- 21. 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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