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- 1. Microelectron. Reliability 46, 1 (2006) , “NBTI degradation: From physical mechanisms to modelling”,An overview of the evolution of transistor parameters under negative bias temperature instability stress conditions commonly observed in p-MOSFETs in recent technologies is presented. The physical mechanisms of the degradation as well as the different defects involved have been discussed according to a systematic set of experiments with different stress conditions. According to our findings, a physical model is proposed which could be used to more accurately predict the transistor degradation. Finally, based on our new present understanding, a new characterization methodology is proposed, which would open the way to a more accurate determination of parameter shifts and thus allowing implementing the degradation into design rules. (Read more)
- 2. Microelectron. Reliability 45, 71 (2005) , “A comprehensive model of PMOS NBTI degradation ”,Negative bias temperature instability has become an important reliability concern for ultra-scaled Silicon IC technology with significant implications for both analog and digital circuit design. In this paper, we construct a comprehensive model for NBTI phenomena within the framework of the standard reaction–diffusion model. We demonstrate how to solve the reaction–diffusion equations in a way that emphasizes the physical aspects of the degradation process and allows easy generalization of the existing work. We also augment this basic reaction–diffusion model by including the temperature and field-dependence of the NBTI phenomena so that reliability projections can be made under arbitrary circuit operating conditions. (Read more)
- 3. J. Appl. Phys. 94, 1 (2003) , “Negative bias temperature instability: Road to cross in deep submicron silicon semiconductor manufacturing”,We present an overview of negative bias temperature instability (NBTI) commonly observed in p-channel metaloxidesemiconductor field-effect transistors when stressed with negative gate voltages at elevated temperatures. We discuss the results of such stress on device and circuit... (Read more)
- 4. 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)
- 5. 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)
- 6. Phys. Rev. B 74, 113301 (2006) , “Reactions of excess hydrogen at a Si(111) surface with H termination: First-principles calculations”, L. Tsetseris, S. T. PantelidesHydrogen reactions with silicon substrates is an established technique for the study and control of surface morphology. Here, we report the results of first-principles calculations on the trapping and depassivation reactions involving excess hydrogen (x-H) at a fully H-passivated Si(111) surface. We find that x-H atoms can depassivate Si-H bonds with a small barrier of 0.8 eV, or they can get trapped in very stable configurations that comprise of a dihydride and a vicinal Si-H bond. Desorption of H2 molecules from these complexes has an activation energy of 1.68 eV, which can account for pertinent experimental data. We discuss also the effect of strain on the possibility of altering the x-H surface profile. (Read more)
- 7. Phys. Rev. Lett. 96, 145501 (2006) , “Identification of the Carbon Antisite-Vacancy Pair in 4H-SiC”, T. Umeda, N. T. Son, J. Isoya, E. Janzn, T. Ohshima, N. Morishita, H. Itoh, A. Gali, M. BockstedteThe metastability of vacancies was theoretically predicted for several compound semiconductors alongside their transformation into the antisite-vacancy pair counterpart; however, no experiment to date has unambiguously confirmed the existence of antisite-vacancy pairs. Using electron paramagnetic resonance and first principles calculations we identify the SI5 center as the carbon antisite-vacancy pair in the negative charge state (CSiVC-) in 4H-SiC. We suggest that this defect is a strong carrier-compensating center in n-type or high-purity semi-insulating SiC. (Read more)SiC| ENDOR EPR Theory electron-irradiation optical-spectroscopy thermal-meas./anneal-exp.| -1 -2 1.0eV~ 13C 29Si C1h C3v Carbon Csi EI5/6 HEI1 HEI5/6 Nitrogen P6/7 SI5 Silicon Vc antisite bistable/metastable dangling-bond n-type pair(=2) semi-insulating vacancy .inp files: SiC/SI5_C1h SiC/SI5_80K SiC/SI5_100K | last update: Takashi Fukushima
- 8. 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)
- 9. Nature 396, 58-60 (1998) , “Interface structure between silicon and its oxide by first-principles molecular dynamics”, A. Pasquarello, M. S. Hybertsen, R. CarThe requirement for increasingly thin (<50 Å) insulating oxide layers in silicon-based electronic devices highlights the importance of characterizing the Si–SiO2 interface structure at the atomic scale. Such a characterization relies to a large extent on an understanding of the atomic-scale mechanisms that govern the oxidation process. The widely used Deal–Grove model invokes a two-step process in which oxygen first diffuses through the amorphous oxide network before attacking the silicon substrate, resulting in the formation of new oxide at the buried interface1. But it remains unclear how such a process can yield the observed near-perfect interface2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12. Here we use first-principles molecular dynamics13, 14, 15 to generate a model interface structure by simulating the oxidation of three silicon layers. The resulting structure reveals an unexpected excess of silicon atoms at the interface, yet shows no bonding defects. Changes in the bonding network near the interface occur during the simulation via transient exchange events wherein oxygen atoms are momentarily bonded to three silicon atoms — this mechanism enables the interface to evolve without leaving dangling bonds. (Read more)
- 10. Phys .Rev. Lett. 92, 178302 (2004) , “Nonvolatile Memory with Multilevel Switching: A Basic Model”, M. J. Rozenberg, I. H. Inoue, and M. J. SánchezThere is a current upsurge in research on nonvolatile two-terminal resistance random access memory (RRAM) for next generation electronic applications. The RRAM is composed of a simple sandwich of a semiconductor with two metal electrodes. We introduce here an initial model for RRAM with the... (Read more)
- 11. Solid State Physics 5, 258-319 (1957) , Academic Press, New York (Edited by F. Seitz, D. Turnbull) , “Shallow Impurity States in Silicon and Germanium”, W. KohnI. Introduction (p.258): II. Emprical Properties (p.261): 1. Energy Levels (p.261), a. Ionization Energies, b. Spectra of Excited States, 2. Spin Resonance (p.266), a. Electron Spin Resonance, b. Double Resonance, 3. Static Magnetic Susceptibility (p.271), III. Structure of Donor States (p.271): 4. Conduction Bands of Silicon and Germanium (p.271), a. Silicon, b. Germanium, 5. Effective Mass Theory of Donor States (p.274), a. Single Band Minimum at k=0, b. Several Conduction Band Minima, c. Matrix Elements for Radiative Transitions, 6. Numerical Results and Comparison with Experiments (p.285), a. Energy Levels, b. Wave Functions, 7. Corrections to the Effective Mass Formalism (p.289), a. General Considerations, b. Corrected Wave Functions, c. Comparison with Experiment, IV. Structure of Acceptor States (p.297): 8. Valence Bands of Silicon and Germanium (p.297), a. Silicon, b. Germanium, 9. Effective Mass Equations for Acceptor States (p.300), 10. Approximate Solutions and Comparison with Experiment (p.301) a. Germanium b. Silicon V.Effects of Strains and of Static Electric and Magnetic Fields (p.306): 11. Strains (p.306) a. Donor States, b. Acceptor States, 12. Stark Effect (p.311)
- 12. phys. stat. sol. (a) 162, 95-151 (1997) , “EPR and ENDOR Investigations of Shallow Impurities in SiC Polytypes”, S. Greulich-WeberInvestigations of nitrogen donors in 6H-, 4H- and 3C-SiC using conventional electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR) and optical detection of EPR and ENDOR as well as optical absorption and emission spectroscopy are reviewed and critically discussed. An... (Read more)
- 13. phys. stat. sol. (b) 210, 415-427 (1998) , “The Microscopic and Electronic Structure of Shallow Donors in SiC”, S. Greulich-WeberNitrogen donors in 6H-, 4H- and 3C-SiC were investigated using conventional electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) and the experimental results are discussed. An attempt is presented to interpret the experimentally found large differences in hyperfine... (Read more)
- 14. 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
- 15. 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)
- 16. 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)
- 17. Phys. Rev. B 73, 033204 (2006) , “Electrical characterization of metastable carbon clusters in SiC: A theoretical study”, A. Gali, N. T. Son, E. JanznFirst-principles calculations carried out in 3C- and 4H-SiC show that small metastable carbon clusters can be created in irradiated SiC. The metastable carbon clusters possess occupation levels in the p-type as well as in the n-type 4H-SiC. Depending on the... (Read more)
- 18. Phys. Rev. B 70, 235211 (2004) , “Structure and vibrational spectra of carbon clusters in SiC”, Alexander Mattausch, Michel Bockstedte, and Oleg PankratovThe electronic, structural, and vibrational properties of small carbon interstitial and antisite clusters are investigated by ab initio methods in 3C- and 4H-SiC. The defects possess sizable dissociation energies and may be formed via condensation of carbon interstitials, e.g.,... (Read more)
- 19. Phys. Rev. Lett. 98, 252501 (2007) , “Radioactive Decay Speedup at T=5 K: Electron-Capture Decay Rate of 7Be Encapsulated in C60”, T. Ohtsuki, K. Ohno, T. Morisato, T. Mitsugashira, K. Hirose, H. Yuki, and J. KasagiThe electron-capture (EC) decay rate of 7Be in C60 at the temperature of liquid helium (T=5 K) was measured and compared with the rate in Be metal at T=293 K. We found that the half-life of 7Be in endohedral C60... (Read more)
- 20. Phys. Rev. Lett. 98, 117202 (2007) , “Density-Functional Theory Study of Half-Metallic Heterostructures: Interstitial Mn in Si”, Hua Wu, Peter Kratzer, and Matthias SchefflerUsing density-functional theory within the generalized gradient approximation, we show that Si-based heterostructures with 1/4 layer δ doping of interstitial Mn (Mnint) are half-metallic. For Mnint concentrations of 1/2 or 1 layer, the states induced in the band... (Read more)
- 21. Phys. Rev. Lett. 98, 115503 (2007) , “Oxygen Vacancy Clustering and Electron Localization in Oxygen-Deficient SrTiO3: LDA+U Study”, Do Duc Cuong, Bora Lee, Kyeong Mi Choi, Hyo-Shin Ahn, Seungwu Han, and Jaichan LeeWe find, using a local density approximation +Hubbard U method, that oxygen vacancies tend to cluster in a linear way in SrTiO3, a prototypical perovskite oxide, accompanied by strong electron localization at the 3d state of the nearby Ti transition metal ion. The vacancy... (Read more)
- 22. 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)
- 23. 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)
- 24. Phys. Rev. B 75, 115205 (2007) , “Stability of I3 complexes in III-V compound semiconductors by tight-binding molecular dynamics”, G. Zollo and F. GalaIntrinsic interstitials in GaAs are known to have a large formation energy that makes their concentration almost negligible in as-grown materials. However, interstitials must be explicitly considered in implanted GaAs where collision cascades, induced by the energetic ions, produce a large amount of... (Read more)
- 25. Phys. Rev. B 75, 115201 (2007) , “Atomistic modeling of the (a+c)-mixed dislocation core in wurtzite GaN”, I. Belabbas, A. Béré, J. Chen, S. Petit, M. Akli Belkhir, P. Ruterana, and G. NouetAn atomistic simulation of the threading (a+c)-mixed dislocation core in wurtzite GaN has been carried out. Starting from models generated in the framework of continuum elasticity theory, two core configurations are obtained independently by using an empirical potential and a... (Read more)
- 26. Phys. Rev. B 75, 115127 (2007) , “Molecular microelectrostatic view on electronic states near pentacene grain boundaries”, Stijn Verlaak and Paul HeremansGrain boundaries are the most inevitable and pronounced structural defects in pentacene films. To study the effect of those structural defects on the electronic state distribution, the energy levels of a hole on molecules at and near the defect have been calculated using a submolecular... (Read more)
- 27. Phys. Rev. B 75, 115113 (2007) , “Structural, electronic, and magnetic properties of Mn-doped Ge nanowires by ab initio calculations”, J. T. Arantes, Antônio J. R. da Silva, and A. FazzioUsing ab initio total energy density-functional theory calculations, we investigated the electronic, structural, and magnetic properties of manganese-doped germanium nanowires. The nanowires have been constructed along the [110] direction and the dangling bonds on the surface have been... (Read more)
- 28. Phys. Rev. B 75, 113401 (2007) , “Enhancing the topological structures of defected carbon nanotubes with adsorbed hydrocarbon radicals at low temperatures”, R. L. Zhou, H. Y. He, and B. C. PanRealistic carbon nanotubes (CNTs) contain various structural defects by which the physical and chemical properties of the CNTs are significantly influenced. So, lowering the defect densities is of importance for the potential application of the CNTs. By performing tight-binding molecular dynamics... (Read more)
- 29. Phys. Rev. B 74, 245420 (2006) , “Energetics, structure, and long-range interaction of vacancy-type defects in carbon nanotubes: Atomistic simulations”, J. Kotakoski, A. V. Krasheninnikov,, and K. NordlundThe presence of vacancy clusters in carbon nanotubes has been assumed to explain the formation of carbon peapods and the difference between the experimentally measured and theoretical fracture strength of nanotubes. We use atomistic simulations at various levels of theory to study the... (Read more)
- 30. Phys. Rev. B 74, 245411 (2006) , “Vacancy defects and the formation of local haeckelite structures in graphene from tight-binding molecular dynamics”, Gun-Do Lee, C. Z. Wang, Euijoon Yoon, Nong-Moon Hwang, and K. M. HoThe dynamics of multivacancy defects in a graphene layer is investigated by tight-binding molecular dynamics simulations and by first principles calculation. The simulations show that four single vacancies in the graphene layer first coalesce into two double vacancies, each consisting of a... (Read more)
- 31. Phys. Rev. B 74, 245216 (2006) , “Influence of excited states of a deep substitutional dopant on majority-carrier concentration in semiconductors”, Hideharu MatsuuraThe density (NA) and energy level (EA) of an acceptor in a p-type wide-band-gap semiconductor (e.g., SiC, GaN, and diamond) are determined by a least-squares fit of the charge neutrality equation to the temperature dependence of the hole... (Read more)
- 32. Phys. Rev. B 74, 241303(R) (2006) , “Enhancement of interactions between magnetic ions in semiconductors due to declustering”, A. Franceschetti, S. V. Barabash, J. Osorio-Guillen, A. Zunger, and M. van SchilfgaardeIt is often assumed that the exchange interaction between two magnetic ions in a semiconductor host depends only on the distance and orientation of the magnetic ions. Using first-principles electronic structure calculations of Mn impurities in GaAs, we show that the exchange interaction between two... (Read more)
- 33. Phys. Rev. B 74, 235426 (2006) , “First-principles study of electronic properties of hydrogenated graphite”, A. Allouche and Y. FerroProgressive implantation of hydrogen atoms into graphite is modeled by first-principles density functional theory. The maximum H/C ratio was found at 53%, which is in good agreement with experimental results. The hydrogen trapping energy varies from −0.7 eV at very low concentrations to a... (Read more)
- 34. Phys. Rev. B 74, 235301 (2006) , “Precursor mechanism for interaction of bulk interstitial atoms with Si(100)”, Xiao Zhang, Min Yu, Charlotte T. M. Kwok, Ramakrishnan Vaidyanathan, Richard D. Braatz, and Edmund G. SeebauerIn the same way that gases react with surfaces from above, solid-state point defects such as interstitial atoms can react from below. Little attention has been paid to this form of surface chemistry. Recent bulk self-diffusion measurements near the Si(100) surface have quantified Si interstitial... (Read more)
- 35. 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)
- 36. Phys. Rev. B 74, 235208 (2006) , “Theoretical study of the magnetism of Mn-doped ZnO with and without defects”, D. Iuan, B. Sanyal, and O. ErikssonWe calculate the exchange interaction parameters of a classical Heisenberg Hamiltonian for Mn-doped ZnO (Mn concentration between 5% and 20%) by an ab initio Korringa-Kohn-Rostoker coherent-potential-approximation method in the framework of density functional theory. A weak antiferromagnetic... (Read more)
- 37. Phys. Rev. B 74, 235207 (2006) , “Vacancy-enhanced ferromagnetism in Fe-doped rutile TiO2”, Jun Chen, Paul Rulis, Lizhi Ouyang, S. Satpathy, and W. Y. ChingBased on a series of supercell density functional calculations of Fe-doped TiO2 both with and without O vacancy (VO), we show that VO plays an important role in determining the magnetic properties of the dilute magnetic semiconductors (DMS). Without... (Read more)
- 38. Phys. Rev. B 74, 233201 (2006) , “Electronic and magnetic properties of V-doped anatase TiO2 from first principles”, Xiaosong Du, Qunxiang Li, Haibin Su, and Jinlong YangWe report a first-principles study on the geometric, electronic, and magnetic properties of V-doped anatase TiO2. The DFT+U (Hubbard coefficient) approach predicts semiconductor band structures for Ti1−xVxO2 (x=6.25% and... (Read more)
- 39. Phys. Rev. B 74, 214109 (2006) , “Inversion of defect interactions due to ordering in Sr1−3x/2LaxTiO3 perovskites: An atomistic simulation study”, B. S. Thomas, N. A. Marks, and Peter HarrowellSr1−3x/2LaxTiO3 perovskites exhibit large variations in radiation resistance and A-site vacancy ordering, depending on x and thermal history. In this study we use a combination of ab initio and classical simulation techniques... (Read more)
- 40. Phys. Rev. B 74, 214105 (2006) , “Atomistic simulations of radiation-induced defect formation in spinels: MgAl2O4, MgGa2O4, and MgIn2O4”, D. Bacorisen, Roger Smith, B. P. Uberuaga, K. E. Sickafus, J. A. Ball, and R. W. GrimesMolecular dynamics simulations of collision cascades were performed in three spinel oxides with varying inversion, namely normal magnesium aluminate, MgAl2O4, half-inverse magnesium gallate, MgGa2O4, and inverse magnesium indate,... (Read more)
- 41. Phys. Rev. B 74, 205324 (2006) , “Surface smoothness of plasma-deposited amorphous silicon thin films: Surface diffusion of radical precursors and mechanism of Si incorporation”, Mayur S. Valipa, Tamas Bakos, and Dimitrios MaroudasWe present a detailed analysis of the fundamental atomic-scale processes that determine the surface smoothness of hydrogenated amorphous silicon (a-Si:H) thin films. The analysis is based on a synergistic combination of molecular-dynamics (MD) simulations of radical precursor migration on surfaces... (Read more)
- 42. Phys. Rev. B 74, 205202 (2006) , “Structural model of amorphous silicon annealed with tight binding”, N. Bernstein, J. L. Feldman,, and M. FornariWe present a model of amorphous silicon generated by extensive annealing of a continuous random network structure using a molecular dynamics simulation with forces computed by a tight-binding total energy method. We also produce a refined model by relaxing the annealed model using density functional... (Read more)
- 43. Phys. Rev. B 74, 165404 (2006) , “Density functional study of gold atoms and clusters on a graphite (0001) surface with defects”, Jaakko Akola and Hannu HäkkinenAdsorption of gold atoms and clusters (N=6) on a graphite (0001) surface with defects has been studied using density functional theory. In addition to perfect graphite (0001), three types of surface defects have been considered: a surface vacancy (hole), a pyridinelike defect comprising three... (Read more)
- 44. Phys. Rev. B 74, 174407 (2006) , “Superexchange in dilute magnetic dielectrics: Application to (Ti,Co)O2”, K. Kikoin and V. FleurovWe extend the model of ferromagnetic superexchange in dilute magnetic semiconductors to the ferromagnetically ordered highly insulating compounds (dilute magnetic dielectrics). The intrinsic ferromagnetism without free carriers is observed in oxygen-deficient films of anatase TiO2 doped... (Read more)
- 45. Phys. Rev. B 74, 174115 (2006) , “Modeling of damage generation mechanisms in silicon at energies below the displacement threshold”, Iván Santos, Luis A. Marqués, and Lourdes PelazWe have used molecular dynamics simulation techniques to study the generation of damage in Si within the low-energy deposition regime. We have demonstrated that energy transfers below the displacement threshold can produce a significant amount of damage, usually neglected in traditional radiation... (Read more)
- 46. Phys. Rev. B 74, 174101 (2006) , “First-principles study of the intrinsic defects in PbFCl”, Bo Liu, Zeming Qi, and Chaoshu ShiFirst-principles pseudopotential calculations have been performed to investigate intrinsic defects including vacancies, interstitials, antisite defects, as well as Schottky and Frenkel defects in PbFCl crystals. For the isolated vacancies and interstitials, their formation energies are critically... (Read more)
- 47. Phys. Rev. Lett. 98, 137202 (2007) , “Magnetizing Oxides by Substituting Nitrogen for Oxygen”, I. S. Elfimov, A. Rusydi, S. I. Csiszar, Z. Hu, H. H. Hsieh, H.-J. Lin, C. T. Chen, R. Liang, and G. A. SawatzkyWe describe a possible pathway to new magnetic materials with no conventional magnetic elements present. The substitution of nitrogen for oxygen in simple nonmagnetic oxides leads to holes in N 2p states which form local magnetic moments. Because of the very large Hund's rule coupling of... (Read more)
- 48. Phys. Rev. Lett. 98, 135506 (2007) , “Possible Approach to Overcome the Doping Asymmetry in Wideband Gap Semiconductors”, Yanfa Yan, Jingbo Li, Su-Huai Wei, and M. M. Al-JassimThe asymmetry doping problem has severely hindered the potential applications of many wideband gap (WBG) materials. Here, we propose a possible approach to overcome this long-standing doping asymmetry problem for WBG semiconductors. Our approach is based on the reduction of the ionization energies... (Read more)
- 49. Phys. Rev. Lett. 98, 196802 (2007) , “Origin of Charge Density at LaAlO3 on SrTiO3 Heterointerfaces: Possibility of Intrinsic Doping”, Wolter Siemons, Gertjan Koster, Hideki Yamamoto, Walter A. Harrison, Gerald Lucovsky, Theodore H. Geballe, Dave H. A. Blank, and Malcolm R. BeasleyAs discovered by Ohtomo and Hwang, a large sheet charge density with high mobility exists at the interface between SrTiO3 and LaAlO3. Based on transport, spectroscopic, and oxygen-annealing experiments, we conclude that extrinsic defects in the form of oxygen vacancies... (Read more)
- 50. Phys. Rev. Lett. 98, 196101 (2007) , “Oxygen Vacancies in High Dielectric Constant Oxide-Semiconductor Films”, Supratik Guha and Vijay NarayananWe provide evidence that the oxygen vacancy is a dominant intrinsic electronic defect in nanometer scaled hafnium oxide dielectric films on silicon, relevant to microelectronics technology. We demonstrate this by developing a general model for the kinetics of oxygen vacancy formation in... (Read more)
- 51. Phys. Rev. B 74, 155208 (2006) , “Vibrational spectra of vitreous germania from first-principles”, Luigi Giacomazzi, P. Umari, and Alfredo PasquarelloWe report on a first-principles investigation of the structural and vibrational properties of vitreous germania (v-GeO2). Our work focuses on a periodic model structure of 168 atoms, but three smaller models are also studied for comparison. We first carry out a detailed structural... (Read more)
- 52. Phys. Rev. B 74, 155201 (2006) , “Crystal-field theory of Co2+ in doped ZnO”, R. O. Kuzian, A. M. Daré, P. Sati, and R. HaynWe present a crystal-field theory of transition-metal impurities in semiconductors in a trigonally distorted tetrahedral coordination. We develop a perturbative scheme to treat covalency effects within the weak ligand field case (Coulomb interaction dominates over one-particle splitting) and apply... (Read more)
- 53. Phys. Rev. B 74, 153403 (2006) , “Doping and the unique role of vacancies in promoting the magnetic ground state in carbon nanotubes and C60 polymers”, Antonis N. Andriotis, R. Michael Sheetz, and Madhu MenonThe role of various types of defects in establishing the magnetic properties of the C60-based polymers and the single-wall carbon nanotubes is investigated. Comparing the role of carbon vacancies, and that of substitutional impurity atoms X (X=N, B, O, Si, P, and S) in... (Read more)
- 54. Phys. Rev. B 74, 195202 (2006) , “Interstitial-mediated mechanisms of As and P diffusion in Si: Gradient-corrected density-functional calculations”, Scott A. Harrison, Thomas F. Edgar, and Gyeong S. HwangGradient-corrected density-functional calculations are used to determine the structure, stability, and diffusion of arsenic-interstitial and phosphorus-interstitial pairs in the positive, neutral, and negative charge states. For both cases, our calculations show that the neutral pair will be... (Read more)
- 55. Phys. Rev. B 74, 193405 (2006) , “Role of charge in destabilizing AlH4 and BH4 complex anions for hydrogen storage applications: Ab initio density functional calculations”, A. J. Du, Sean C. Smith, and G. Q. LuNaAlH4 and LiBH4 are potential candidate materials for mobile hydrogen storage applications, yet they have the drawback of being highly stable and desorbing hydrogen only at elevated temperatures. In this letter, ab initio density functional theory calculations reveal... (Read more)
- 56. Phys. Rev. B 74, 184117 (2006) , “Ab initio thermodynamic properties of point defects and O-vacancy diffusion in Mg spinels”, Zbigniew odziana and Jacek PiechotaWe report ab initio plane wave density functional theory studies of thermodynamic properties of isolated cation substitutions and oxygen vacancies in magnesium spinel, MgAl2O4. The formation enthalpy of Ca, Cu, and Zn substitutions of Mg cation indicate that transition... (Read more)
- 57. Phys. Rev. B 74, 184108 (2006) , “Interpreting Mössbauer spectra reflecting an infinite number of sites: An application to Fe1−xSi synthesized by pulsed laser annealing”, A. Falepin, S. Cottenier, C. M. Comrie, and A. VantommeWe present a study on the interpretation of conversion electron Mössbauer spectra reflecting an infinite number of sites, in casu Mössbauer spectroscopy on Fe1−xSi layers on Si, synthesized by pulsed laser annealing. These spectra display a broad... (Read more)
- 58. Phys. Rev. B 75, 195335 (2007) , “Computational and experimental imaging of Mn defects on GaAs (110) cross-sectional surfaces”, A. Stroppa, X. Duan, M. Peressi, D. Furlanetto, and S. ModestiWe present a combined experimental and computational study of the (110) cross-sectional surface of Mn δ-doped GaAs samples. We focus our study on three different selected Mn defect configurations not previously studied in detail, namely surface interstitial Mn, isolated and in pairs, and... (Read more)
- 59. Phys. Rev. B 75, 195215 (2007) , “Effect of Co and O defects on the magnetism in Co-doped ZnO: Experiment and theory”, G. S. Chang, E. Z. Kurmaev, D. W. Boukhvalov, L. D. Finkelstein, S. Colis, T. M. Pedersen, A. Moewes, and A. DiniaThe electronic structure of Zn1−xCoxO (x=0.02, 0.06, and 0.10) diluted magnetic semiconductors is investigated using soft x-ray emission spectroscopy and first-principles calculations. X-ray absorption and emission measurements reveal that most Co... (Read more)
- 60. Phys. Rev. B 75, 195208 (2007) , “Supercell and cluster density functional calculations of the thermal stability of the divacancy in germanium”, C. Janke, R. Jones, S. Öberg, and P. R. BriddonLarge vacancy clusters, or voids, formed during crystal growth have been reported in Ge. The divacancy is a precursor to such clusters, and is believed to be stable up to 150 or 180 °C. It is also believed to form in Ge irradiated at room temperature where single vacancies are mobile. Density... (Read more)
- 61. Phys. Rev. B 75, 195206 (2007) , “Effect of defect-enhanced molecular oxygen adsorption on the imbalance of hole versus electron mobility in conjugated polymers”, Chi-Ken Lu, Shu-Ting Pi, and Hsin-Fei MengThe generally observed higher hole mobility relative to electron mobility in conjugated polymers is explained with the defects and adsorbed molecular oxygen. Adsorption of the extrinsic molecular oxygen leads to that electrons are bound more tightly than holes by the traps in the originally... (Read more)
- 62. Phys. Rev. B 75, 193409 (2007) , “Magnetic properties of vacancies in a graphitic boron nitride sheet by first-principles pseudopotential calculations”, M. S. Si and D. S. XueWe use ab initio methods to calculate the magnetic properties of vacancies in a graphitic boron nitride sheet (g-BN). By applying a full spin-polarized description to the system, we demonstrate that the nitrogen vacancy (VN) or the boron vacancy (VB)... (Read more)
- 63. Phys. Rev. B 75, 193203 (2007) , “Hf defects in c-Si and their importance for the HfO2/Si interface: Density-functional calculations”, Wanderlã L. Scopel, Antônio J. R. da Silva, and A. FazzioWe have studied, using ab initio density functional theory calculations, substitutional and interstitial Hf impurities in c-Si, for various charge states. Our results indicate that (1) the tetrahedral interstitial defect is energetically more favorable than the substitutional and (2)... (Read more)
- 64. Phys. Rev. B 75, 144404 (2007) , “Ferromagnetism in Fe-doped ZnO nanocrystals: Experiment and theory”, Debjani Karmakar, S. K. Mandal, R. M. Kadam, P. L. Paulose, A. K. Rajarajan, T. K. Nath, A. K. Das, I. Dasgupta, and G. P. DasFe-doped ZnO nanocrystals are successfully synthesized and structurally characterized by using x-ray diffraction and transmission electron microscopy. Magnetization measurements on the same system reveal a ferromagnetic to paramagnetic transition temperature above 450 K with a low-temperature... (Read more)
- 65. Phys. Rev. B 75, 144108 (2007) , “Interaction mechanism between edge dislocations and asymmetrical tilt grain boundaries investigated via quasicontinuum simulations”, T. Shimokawa, T. Kinari, and S. ShintakuThe interactions between edge dislocations and grain boundaries—dislocation pileup, dislocation absorption, and dislocation transmission—are studied by performing quasicontinuum simulations. The 112 asymmetrical tilt grain boundaries with different misorientation angles are used. The... (Read more)
- 66. Phys. Rev. B 75, 144103 (2007) , “Multiscale modeling of point defects in Si-Ge(001) quantum wells”, B. Yang and V. K. TewaryA computationally efficient hybrid Green's function (GF) technique is developed for multiscale modeling of point defects in a trilayer lattice system that links seamlessly the length scales from lattice (subnanometers) to continuum (bulk). The model accounts for the discrete structure of the lattice... (Read more)
- 67. Phys. Rev. B 75, 144102 (2007) , “Theoretical investigation of nitrogen substitution in cubic zirconia”, Thomas BredowNitrogen substitution of oxygen ions in cubic zirconia was studied theoretically at density functional level. Nitrogen contents of 12.5 and 3.1% were studied with Zr8O16−mN2 and Zr32O64−mN2 supercells. For... (Read more)
- 68. Phys. Rev. B 75, 134106 (2007) , “Exact linear response of reacting thermal defects driven by creation processes”, C. P. FlynnThe exact, linear response at steady state is calculated for reacting, but otherwise noninteracting, thermal defects driven by defect creation processes. The theory applies to vacancies and interstitials in the bulk, or to adatoms and advacancies on surface terraces. A wide variety of possible... (Read more)
- 69. Phys. Rev. B 75, 024205 (2007) , “Mechanical strength and coordination defects in compressed silica glass: Molecular dynamics simulations”, Yunfeng Liang, Caetano R. Miranda, and Sandro ScandoloContrary to ordinary solids, which are normally known to harden by compression, the compressibility of SiO2 (silica) glass has a maximum at about 2–4 GPa and its mechanical strength shows a minimum around 10 GPa. At this pressure, the compression of silica glass undergoes a change... (Read more)
- 70. Phys. Rev. B 75, 014111 (2007) , “Effects of vacancies on the properties of disordered ferroelectrics: A first-principles study”, L. Bellaiche, Jorge Íñiguez, Eric Cockayne, and B. P. BurtonA first-principles-based model is developed to investigate the influence of lead vacancies on the properties of the disordered Pb(Sc1/2Nb1/2)O3 (PSN) ferroelectric. Lead vacancies generate large, inhomogeneous, electric fields that reduce barriers between energy... (Read more)
- 71. Phys. Rev. B 75, 014102 (2007) , “First-principles study of vacancy formation in hydroxyapatite”, Katsuyuki Matsunaga and Akihide KuwabaraFirst-principles plane-wave calculations were performed for hydroxyapatite (HAp) in order to investigate the electronic structure and vacancy formation mechanisms. The HAp unit cell contains PO4 tetrahedra and OH groups formed by covalent P-O and H-O bonds. Ca ions play a role for... (Read more)
- 72. Phys. Rev. B 75, 035322 (2007) , “Ab initio study of electronic and magnetic properties of the C-codoped Ga1−xMnxN (100) surface”, Q. Wang, Q. Sun, and P. JenaFirst principles calculations based on gradient corrected density functional theory have been carried out to study the magnetic coupling between Mn atoms in pure and carbon doped Ga1−xMnxN thin films. We show that the ground state of Mn-doped GaN (100) thin... (Read more)
- 73. 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)
- 74. Phys. Rev. B 75, 035210 (2007) , “Self- and foreign-atom diffusion in semiconductor isotope heterostructures. I. Continuum theoretical calculations”, H. BrachtDopant diffusion experiments in semiconductors yield the mobility of the element of interest and information about the possible mechanisms of atomic diffusion. In many cases the diffusion is described on the basis of Fick's law of diffusion, but this treatment is often too simple. In this paper,... (Read more)
- 75. Phys. Rev. B 75, 033303 (2007) , “Excitons in silicon nanocrystallites: The nature of luminescence”, Eleonora Luppi, Federico Iori, Rita Magri, Olivia Pulci, Stefano Ossicini, Elena Degoli, and Valerio OlevanoThe absorption and emission spectra of silicon nanocrystals up to 1 nm diameter have been calculated within a first-principles framework. Our calculations include geometry optimization and the many-body effects induced by the creation of an electron-hole pair. Starting from hydrogenated silicon... (Read more)
- 76. Phys. Rev. B 75, 045201 (2007) , “Ab initio models of amorphous Si1−xGex:H”, T. A. Abtew and D. A. DraboldWe study the structural, dynamical, and electronic properties of amorphous Si1−xGex:H alloys using first-principles local basis molecular dynamics techniques. The network topology and defects in the amorphous network have been analyzed. Structural changes,... (Read more)
- 77. Phys. Rev. Lett. 98, 045501 (2007) , “Dopability, Intrinsic Conductivity, and Nonstoichiometry of Transparent Conducting Oxides”, Stephan Lany and Alex ZungerExisting defect models for In2O3 and ZnO are inconclusive about the origin of conductivity, nonstoichiometry, and coloration. We apply systematic corrections to first-principles calculated formation energies ΔH, and validate our theoretical defect model against... (Read more)
- 78. Phys. Rev. Lett. 98, 075503 (2007) , “Pseudoclimb and Dislocation Dynamics in Superplastic Nanotubes”, Feng Ding, Kun Jiao, Mingqi Wu, and Boris I. YakobsonPlastic relaxation of carbon nanotubes under tension and at high temperature is described in terms of dislocation theory and with atomistic computer simulations. It is shown how the glide of pentagon-heptagon defects and a particular type of their pseudoclimb, with the atoms directly breaking out of... (Read more)
- 79. Phys. Rev. B 75, 075420 (2007) , “Ab initio study of hydrogen interaction with pure and nitrogen-doped carbon nanotubes”, Zhiyong Zhang and Kyeongjae ChoDetailed studies of mechanisms for hydrogen dissociative adsorption and diffusion on pure and nitrogen-doped (8, 0) carbon nanotubes are carried out using the first-principles density functional theory method. (1) For pure carbon nanotubes, we have identified the energetically most favorable... (Read more)
- 80. Phys. Rev. B 75, 075316 (2007) , “Theoretical investigation of a Mn-doped Si/Ge heterostructure”, J. T. Arantes, Antônio J. R. da Silva, A. Fazzio, and A. AntonelliWe investigate, through ab initio density-functional theory calculations, the electronic and structural properties of neutral Mn impurities at tetrahedral interstitial and substitutional sites in both Si and Ge layers of a Si/Ge heterostructure. We conclude that substitutional Mn at the Ge... (Read more)
- 81. Phys. Rev. B 75, 075312 (2007) , “Ferromagnetic to ferrimagnetic crossover in Cr-doped GaN nanohole arrays”, Q. Wang, Q. Sun, P. Jena, and Y. KawazoeUsing spin-polarized density-functional theory with exchange and correlation potential, approximated by both the generalized gradient approximation (GGA) and the GGA+U methods, we show that the coupling between a pair of Cr atoms substituted in GaN nanoholes is ferromagnetic. The interaction between... (Read more)
- 82. Phys. Rev. B 75, 075206 (2007) , “Isotope dependence of the vibrational lifetimes of light impurities in Si from first principles”, D. West and S. K. EstreicherThe vibrational lifetimes of a range of H-related defects and interstitial O (Oi) in Si, including isotopic substitutions, are calculated from first principles as a function of temperature. The theoretical approach is explained in detail. The vibrational lifetimes of... (Read more)
- 83. Phys. Rev. B 75, 075202 (2007) , “Theoretical study of Li and Na as n-type dopants for diamond”, J. P. Goss and P. R. BriddonPhosphorus is the n-type dopant of choice for diamond, but results in a deep donor level and alternatives are being sought. One possibility is the incorporation of interstitial alkali metal impurities such as Li and Na. We present the results of density-functional calculations used to predict... (Read more)
- 84. Phys. Rev. B 75, 073409 (2007) , “Why thermal H2 molecules adsorb on SiC(001)-c(4×2) and not on SiC(001)-(3×2) at room temperature”, Xiangyang Peng, Peter Krüger, and Johannes PollmannIn a recent experiment, Derycke et al. have made the exciting observation that H2 molecules readily adsorb dissociatively on the c(4×2) but not on the 3×2 surface of SiC(001) at room temperature. To unravel this spectacular reactivity difference, we have investigated a... (Read more)
- 85. Phys. Rev. B 75, 073203 (2007) , “Diffusion mechanisms of native point defects in rutile TiO2: Ab initio total-energy calculations”, Hakim Iddir, Serdar Öüt, Peter Zapol, and Nigel D. BrowningThe structural energetics and diffusion mechanisms of the two most important point defects in rutile TiO2, the oxygen vacancy (VO) and the titanium interstitial (TiI), are examined using the ab initio pseudopotential total-energy method. The two... (Read more)
- 86. Phys. Rev. B 75, 085439 (2007) , “Real-space investigation of fast diffusion of hydrogen on Si(001) by a combination of nanosecond laser heating and STM”, C. H. Schwalb, M. Lawrenz, M. Dürr,, and U. HöferThe rearrangement of silicon dangling bonds induced by pulsed laser heating of monohydride-covered Si(001) surfaces has been studied by means of scanning tunneling microscopy (STM). The initial configurations, which were created by laser-induced thermal desorption, consist of isolated pairs of... (Read more)
- 87. Phys. Rev. B 75, 085416 (2007) , “Ab initio theoretical study of hydrogen and its interaction with boron acceptors and nitrogen donors in single-wall silicon carbide nanotubes”, A. GaliSilicon carbide nanotubes have a great potential for biological applications. It is of interest to explore the electronic properties of these nanotubes, and how those are modified in the presence of impurities. Hydrogen is a common impurity that can appear during the growth of silicon carbide... (Read more)
- 88. Phys. Rev. B 75, 085204 (2007) , “Internal structure of the neutral donor-bound exciton complex in cubic zinc-blende and wurtzite semiconductors”, Bernard Gil, Pierre Bigenwald, Mathieu Leroux, Plamen P. Paskov, and Bo MonemarWe calculate the fine structure splitting of the near band edge donor-bound excitons in major cubic semiconductors using an approach inspired by an earlier one that consists in replacing the Morse potential by a Kratzer one, in order to account for the repulsion between the donor and the hole. A... (Read more)
- 89. Phys. Rev. Lett. 98, 015501 (2007) , “First-Principles Simulations of Boron Diffusion in Graphite”, I. Suarez-Martinez, A. A. El-Barbary, G. Savini, and M. I. HeggieBoron strongly modifies electronic and diffusion properties of graphite. We report the first ab initio study of boron interaction with the point defects in graphite, which includes structures, thermodynamics, and diffusion. A number of possible diffusion mechanisms of boron in graphite are... (Read more)
- 90. Phys. Rev. Lett. 97, 256602 (2006) , “Bistability-Mediated Carrier Recombination at Light-Induced Boron-Oxygen Complexes in Silicon”, Mao-Hua Du, Howard M. Branz, Richard S. Crandall, and S. B. ZhangA first-principles study of the BO2 complex in B-doped Czochralski Si reveals a defect-bistability-mediated carrier recombination mechanism, which contrasts with the standard fixed-level Shockley-Read-Hall model of recombination. An O2 dimer distant from B causes only weak... (Read more)
- 91. Phys. Rev. Lett. 97, 255902 (2006) , “Atomistic Mechanism of Boron Diffusion in Silicon”, Davide De Salvador, Enrico Napolitani, Salvatore Mirabella, Gabriele Bisognin, Giuliana Impellizzeri, Alberto Carnera, and Francesco PrioloB diffuses in crystalline Si by reacting with a Si self-interstitial (I) with a frequency g and so forming a fast migrating BI complex that can migrate for an average length λ. We experimentally demonstrate that both g and λ strongly depend on the free hole... (Read more)
- 92. Phys. Rev. Lett. 97, 226401 (2006) , “Quasiparticle Corrections to the Electronic Properties of Anion Vacancies at GaAs(110) and InP(110)”, Magnus Hedström, Arno Schindlmayr, Günther Schwarz, and Matthias SchefflerWe propose a new method for calculating optical defect levels and thermodynamic charge-transition levels of point defects in semiconductors, which includes quasiparticle corrections to the Kohn-Sham eigenvalues of density-functional theory. Its applicability is demonstrated for anion vacancies at... (Read more)
- 93. 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)
- 94. Phys. Rev. B 74, 045213 (2006) , “Hyperfine interaction and magnetoresistance in organic semiconductors”, Y. Sheng, T. D. Nguyen, G. Veeraraghavan, Ö. Mermer, M. Wohlgenannt, S. Qiu, and U. ScherfWe explore the possibility that hyperfine interaction causes the recently discovered organic magnetoresistance (OMAR) effect. We deduce a simple fitting formula from the hyperfine Hamiltonian that relates the saturation field of the OMAR traces to the hyperfine coupling constant. We compare the... (Read more)
- 95. Appl. Phys. Lett. 88, 091919 (2006) , “Calculation of deep carrier traps in a divacancy in germanium crystals”, J. Coutinho, V. J. B. Torres, R. Jones, A. Carvalho, S. berg, P. R. BriddonWe present an ab initio density functional study on the electronic structure and electrical properties of divacancies in Ge. Although suffering essentially different Jahn-Teller distortions when compared to the analogous defect in Si, the relative location of the electrical levels in the gap... (Read more)
- 96. Appl. Phys. Lett. 90, 021920 (2007) , “Hydrogen passivation of nitrogen in GaNAs and GaNP alloys: How many H atoms are required for each N atom?”, I. A. Buyanova, W. M. Chen, M. Izadifard, S. J. Pearton, C. Bihler, M. S. Brandt, Y. G. Hong, and C. W. TuSecondary ion mass spectrometry and photoluminescence are employed to evaluate the origin and efficiency of hydrogen passivation of nitrogen in GaNAs and GaNP. The hydrogen profiles are found to closely follow the N distributions, providing unambiguous evidence for their preferential binding as the... (Read more)
- 97. Appl. Phys. Lett. 90, 032906 (2007) , “Large scale ab initio molecular dynamics simulations of hydrogen-induced degradation of Ta diffusion barriers in ultralow-k dielectric systems”, Ling Dai, V. B. C. Tan, Shuo-Wang Yang, Ping Wu, and Xian-Tong ChenIn ultralow-k dielectric systems, the porous dielectrics are normally sealed by a SiC film before the deposition of a Ta diffusion barrier layer. However, the Ta barrier effects are negated when the SiC films are fabricated by plasma-enhanced chemical vapor deposition (PECVD). Through large... (Read more)
- 98. Appl. Phys. Lett. 90, 023112 (2007) , “Electrically tunable defects in metallic single-walled carbon nanotubes”, Ji-Yong ParkA defect whose electron transmission probability can be controlled by electric field is intentionally created on a metallic single-walled carbon nanotube (SWCNT) with a voltage pulse from a tip of an atomic force microscope (AFM). Localized characteristics of the created defect are elucidated with... (Read more)
- 99. J. Appl. Phys. 101, 024101 (2007) , “Defect states in the high-dielectric-constant gate oxide HfSiO4”, K. Xiong, Y. Du, K. Tse, and J. RobertsonHafnium silicate has a high dielectric constant and is a leading candidate to act as a gate dielectric. The defect energy levels have been calculated. The oxygen vacancy is found to give rise to Si-like levels which lie within the band gap of Si. The vacancy states are very localized and are... (Read more)
- 100. Appl. Phys. Lett. 90, 042105 (2007) , “Stress induced leakage current mechanism in thin Hf-silicate layers”, A. Paskaleva, M. Lemberger, and A. J. BauerStress induced leakage current (SILC) in thin Hf-silicate layers and the mechanisms of its creation are examined. A very strong polarity and thickness dependence as well as partial recovery of SILC are observed. It is suggested that the trapping in preexisting sites influences SILC by two ways: (1)... (Read more)
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