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- 1. 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)
- 2. Phys. Rev. B 75, 115418 (2007) , “Early stages of radiation damage in graphite and carbon nanostructures: A first-principles molecular dynamics study”, Oleg V. Yazyev, Ivano Tavernelli, Ursula Rothlisberger, and Lothar HelmUnderstanding radiation-induced defect formation in carbon materials is crucial for nuclear technology and for the manufacturing of nanostructures with desired properties. Using first-principles molecular dynamics, we perform a systematic study of the nonequilibrium processes of radiation damage in... (Read more)
- 3. Phys. Rev. B 75, 045211 (2007) , “Ab initio supercell calculations on aluminum-related defects in SiC”, A. Gali, T. Hornos, N. T. Son, E. Janzén, and W. J. ChoykeAb initio supercell calculations of the binding energies predict complex formation between aluminum and carbon interstitials in SiC. In high-energy implanted SiC aluminum acceptor can form very stable complexes with two carbon interstitials. We also show that carbon vacancy can be attached to... (Read more)
- 4. 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)
- 5. 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)
- 6. Phys. Rev. B 74, 235201 (2006) , “Annealing of multivacancy defects in 4H-SiC”, W. E. Carlos, N. Y. Garces, E. R. Glaser, and M. A. FantonThe annealing behavior of defects observed in electron paramagnetic resonance (EPR) and photoluminescence (PL) is discussed. We consider the divacancy (the P6/P7 EPR centers) and a previously unreported EPR center that we suggest is a VC-VSi-VC... (Read more)
- 7. Phys. Rev. B 73, 235213 (2006) , “Donor-vacancy complexes in Ge: Cluster and supercell calculations”, J. Coutinho, S. Öberg, V. J. B. Torres, M. Barroso, R. Jones, and P. R. BriddonWe present a comprehensive spin-density functional modeling study of the structural and electronic properties of donor-vacancy complexes (PV, AsV, SbV, and BiV) in Ge crystals. Special attention is paid to spurious results which are related to the choice of the boundary... (Read more)
- 8. 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)
- 9. 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)
- 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. 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)
- 13. Phys. Rev. B 70, 195344 (2004) , “Ab initio study of structural and electronic properties of planar defects in Si and SiC”, C. Raffy, J. Furthmüller, J.-M. Wagner, and F. BechstedtWe present ab initio calculations for internal interfaces in Si and SiC. Density-functional calculations within the local-density approximation and the pseudopotential-plane-wave approach are performed to understand the effect of such two-dimensional defects on the electronic properties. We... (Read more)
- 14. Phys. Rev. B 69, 235202 (2004) , “Ab initio study of the annealing of vacancies and interstitials in cubic SiC: Vacancy-interstitial recombination and aggregation of carbon interstitials”, Michel Bockstedte, Alexander Mattausch, and Oleg PankratovThe annealing kinetics of mobile intrinsic defects in cubic SiC is investigated by an ab initio method based on density-functional theory. The interstitial-vacancy recombination, the diffusion of vacancies, and interstitials to defect sinks (e.g., surfaces or dislocations) as well as the... (Read more)
- 15. 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)
- 16. Phys. Rev. B 68, 155208 (2003) , “Theoretical study of vacancy diffusion and vacancy-assisted clustering of antisites in SiC”, E. Rauls, Th. Frauenheim, A. Gali, P. DeákUsing the self-consistent-charge density-functional-based tight-binding (SCC-DFTB) method, we have investigated the migration of vacancies at high temperatures, taking into account the entropy contribution to the Gibbs free energy. We have found that the energy barrier for sublattice migration of... (Read more)
- 17. Phys. Rev. B 67, 205202 (2003) , “Formation and annealing of nitrogen-related complexes in SiC”, U. Gerstmann, E. Rauls, Th. Frauenheim, and H. OverhofWe propose a mechanism for the annealing of vacancy-related defects in SiC, based on ab initio total energy calculations. Our mechanism is based on the formation and migration of carbon and nitrogen split interstitials resulting in CSi(NC)n or... (Read more)
- 18. 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)
- 19. Phys. Rev. B 63, 245202 (2001) , “Ab initio density-functional supercell calculations of hydrogen defects in cubic SiC”, B. Aradi, A. Gali, P. Deák, J. E. Lowther, N. T. Son, E. Janzén, W. J. ChoykeBased on ab initio density-functional calculations in supercells of 3C-SiC, the stable configurations of hydrogen and dihydrogen defects have been established. The calculated formation energies are used to give semiquantitative estimates for the concentration of hydrogen in SiC after chemical vapor... (Read more)
- 20. Phys. Rev. B 61, 4659-4666 (2000) , “Identification of the Oxygen-Vacancy Defect Containing a Single Hydrogen Atom in Crystalline Silicon”, P. Johannesen, B. Bech Nielsen, J. R. Byberg.Float-zone and Czochralski-grown silicon crystals have been implanted with protons or deuterons at ?50 K. Electron paramagnetic resonance measurements reveal a new signal in the spectrum of the Czochralski-grown (oxygen-rich) material. This signal is strongly temperature dependent, displaying a... (Read more)
- 21. Phys. Rev. B 61, 2657 (2000) , “Divacancy-Tin Complexes in Electron-Irradiated Silicon Studied by EPR”, M. Fanciulli, J. R. Byberg.n- and p-type float-zone silicon containing 1018-cm-3 tin were irradiated with 2 MeV electrons to a dose of 1018 cm-2 and subsequently examined by electron paramagnetic resonance (EPR). The p-type material yields only the well-known Si-G29 signal due to... (Read more)
- 22. Phys. Rev. B 59, 10823-10829 (1999) , “Defect energy levels in electron-irradiated and deuterium-implanted 6H silicon carbide”, M. O. Aboelfotoh, J. P. DoyleUsing deep-level transient spectroscopy, we studied defect energy levels and their annealing behavior in nitrogen-doped 6H-SiC epitaxial layers irradiated with 2-MeV electrons and implanted with 300-KeV deuterium or hydrogen at room temperature. Five levels located at Ec-0.34,... (Read more)
- 23. Phys. Rev. B 38, 3395-3399 (1988) , “Electrical and Optical Properties of Defects in Silicon Introduced by High-Temperature Electron Irradiation”, Jian-Guo Xu, Fang Lu, and Heng-Hui Sun2-MeV electron irradiation of Si at elevated temperature creates a dominant deep level at the energy Ec-0.36 eV in addition to the oxygen vacancies. This level, which is less significant in room-temperature-irradiated Si, is found to be an efficient recombination center in the present... (Read more)
- 24. J. Appl. Phys. 54, 179-183 (1983) , “The Mechanism of the Enhancement of Divacancy Production by Oxygen During Electron Irradiation of Silicon. II. Computer Modeling”, G. S. Oehrlein, I. Krafcsik, J. L. Lindström, A. E. Jaworowski, and J. W. CorbettNumerical tests of possible models for the oxygen dependence of the divacancy introduction rate in silicon electron irradiated at room temperature were performed on a computer. Only the model in which oxygen traps Si self-interstitials can reproduce all the experimental data. Our modeling results... (Read more)
- 25. 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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