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- 501. J. Appl. Phys. 99, 053516 (2006) , “Correlation between Zn vacancies and photoluminescence emission in ZnO films”, A. Zubiaga, J. A. García, F. Plazaola, F. Tuomisto, K. Saarinen, J. Zuñiga Pérez, and V. Muñoz-SanjoséPhotoluminescence and positron annihilation spectroscopy have been used to characterize and identify vacancy-type defects produced in ZnO films grown on sapphire by metal-organic chemical-vapor deposition. The photoluminescence of the samples in the near band edge region has been studied, paying... (Read more)
- 502. J. Appl. Phys. 99, 053502 (2006) , “Spectroscopic analysis of defects in chlorine doped polycrystalline CdTe”, V. Consonni, G. Feuillet, and S. RenetThe effects of Cl doping of thick polycrystalline CdTe layers grown by close space sublimation on their crystalline structure and the compensation and passivation processes have been investigated. From an extensive low temperature photoluminescence study, it is shown that, in polycrystalline... (Read more)
- 503. 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)
- 504. J. Appl. Phys. 99, 043509 (2006) , “Influence of metal trapping on the shape of cavities induced by high energy He+ implantation”, R. El Bouayadi, G. Regula, M. Lancin, B. Pichaud, and M. DesvignesIn He implantation induced cavities highly contaminated with metals (Au, Ni, Pt) we found that, when no three-dimensional structure is observed, the shape of the cavities can be strongly modified depending on the nature of the metal and on its trapped quantity. The equilibrium shape of cavities is... (Read more)
- 505. J. Appl. Phys. 99, 033701 (2006) , “Diffusion length and junction spectroscopy analysis of low-temperature annealing of electron irradiation-induced deep levels in 4H-SiC”, A. Castaldini, A. Cavallini, L. Rigutti, S. Pizzini, A. Le Donne, and S. BinettiThe effects of low-temperature annealing in 8.2 MeV electron-irradiated 4H-SiC Schottky diodes were investigated. Deep-level transient spectroscopy and minority-carrier diffusion length (Ld) measurements were carried out on not-irradiated samples and on irradiated... (Read more)
- 506. J. Appl. Phys. 99, 023702 (2006) , “Deep traps in oxide-nitride-oxide stacks fabricated from hydrogen and deuterium containing precursors”, G. Rosenman, M. Naich, Ya. Roizin, and Rob van SchaijkThe energy spectrum of the traps and thermal stability of stored charge have been studied by the thermostimulated exoelectron emission method in hydrogenated H and deuterated D oxide-nitride-oxide (ONO) multilayer stacks of silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memories. It is... (Read more)
- 507. J. Appl. Phys. 99, 023523 (2006) , “Characterization of 6H-SiC surfaces after ion implantation and annealing using positron annihilation spectroscopy and atomic force microscopy”, G. Brauer, W. Anwand, W. Skorupa, S. Brandstetter, and C. TeichertSystematic slow positron implantation spectroscopy (SPIS) and atomic force microscopy studies of various 6H-SiC samples are presented to clarify the role of conductivity type, crystal quality, ion implantation (B+,Al+, and N+), and annealing (1.650 °C) in... (Read more)
- 508. J. Appl. Phys. 99, 013701 (2006) , “Electronically activated boron-oxygen-related recombination centers in crystalline silicon”, Karsten Bothe and Jan SchmidtTwo different boron- and oxygen-related recombination centers are found to be activated in crystalline silicon under illumination or electron injection in the dark, both leading to a severe degradation in the carrier lifetime. While one center forms on a time scale of seconds to minutes, the... (Read more)
- 509. J. Appl. Phys. 99, 013515 (2006) , “Defects and electrical behavior in 1 MeV Si+-ion-irradiated 4H–SiC Schottky diodes”, F. Roccaforte, S. Libertino, V. Raineri, A. Ruggiero, V. Massimino, and L. CalcagnoIn this paper, the formation and evolution of defects induced by ion irradiation with 1 MeV Si+ ions in Ni2Si/4HSiC Schottky diodes were studied and correlated with the electrical properties of the contacts. The current-voltage characteristics of the contacts... (Read more)
- 510. J. Appl. Phys. 99, 013508 (2006) , “Residual impurities and native defects in 6H-SiC bulk crystals grown by halide chemical-vapor deposition”, S. W. Huh, H. J. Chung, S. Nigam, A. Y. Polyakov, Q. Li, M. Skowronski, E. R. Glaser, W. E. Carlos, B. V. Shanabrook, M. A. Fanton, and N. B. SmirnovA variety of defect-sensitive techniques have been employed to detect, identify, and quantify the residual impurities and native defects in high-purity (undoped) 6H-SiC crystals grown by halide chemical-vapor deposition technique. The incorporation efficiencies of N and B are determined by... (Read more)
- 511. J. Appl. Phys. 99, 013502 (2006) , “Luminescence of bound excitons in epitaxial ZnO thin films grown by plasma-assisted molecular beam epitaxy”, Y. S. Jung, W. K. Choi, O. V. Kononenko, and G. N. PaninLuminescence properties of ZnO films, which have been epitaxially grown on c-sapphire (0001) substrates by plasma-assisted molecular beam epitaxy, are investigated by means of different excitation sources and their measurement conditions. With the increase of measurement temperature,... (Read more)
- 512. J. Appl. Phys. 99, 011101 (2006) , “Degradation of hexagonal silicon-carbide-based bipolar devices”, M. Skowronski and S. HaOnly a few years ago, an account of degradation of silicon carbide high-voltage p-i-n diodes was presented at the European Conference on Silicon Carbide and Related Compounds (Kloster Banz, Germany, 2000). This report was followed by the intense effort of multiple groups... (Read more)
- 513. J. Phys. Chem. Solids 67, 789 (2006) , “Spectroscopic and magnetic studies of manganese ions in ZnO–Sb2O3–B2O3 glass system”, M. Srinivasa Reddy, G. Murali Krishna , N. VeeraiahZnO–Sb2O3–B2O3 glasses containing different concentrations of MnO ranging from 0 to 1.0 mol% were prepared. A number of studies, viz. optical absorption, infrared and ESR spectra and magnetic susceptibility, were carried out as a function of manganese ion concentration. The analysis of... (Read more)
- 514. J. Phys.: Condens. Matter 18, L551 (2006) , IOP Publishing , “Observation of a new high-pressure semimetal phase of GaAs from pressure dependence of the thermopower”, S.V. Ovsyannikov, V.V. ShchennikovWe report the use of the thermopower technique (Seebeck effect) as an effective tool for discovery of 'hidden' (for standard techniques, like x-ray, synchrotron, Raman, etc) phases of substances. Applying the thermopower technique to a set of GaAs single crystals pressurized in a sintered diamond... (Read more)
- 515. Jpn. J. Appl. Phys. 45, L991 (2006) , “Lowering the Switching Current of Resistance Random Access Memory Using a Hetero Junction Structure Consisting of Transition Metal Oxides”, Kentaro Kinoshita, Tetsuro Tamura, Masaki Aoki, Yoshihiro Sugiyama and Hitoshi TanakaBoth lowering the “reset” current of resistance random access memory (ReRAM) and raising the resistance in the low resistance state are crucial for practical use of ReRAM. These requirements have been satisfied by using a hetero junction structure consisting of transition metal oxides, NiOy/TiOx/Pt, combining direct contact with the NiOy using a W-probe. It is considered that this configuration brought about extreme downsizing of the effective area of both the top and bottom electrodes for NiOy and thus decreased the number of filaments formed in “forming” process. Reducing the number of filaments is essential to these issues. (Read more)
- 516. Mater. Sci. Eng. B 126, 222-225 (2006) , “Magnetic properties of a new spintronic material—GaN:Fe”, H. Przybylińska, A. Wolos, M. Kiecana, M. Sawicki, T. Dietl, H. Malissa, C. Simbrunner, M. Wegscheider, H. Sitter, K. Rumpf, P. Granitzer, H. Krenn and W. JantschWe report on metal-organic chemical vapour deposition growth of GaN:Fe and its characterization by means of high-resolution X-ray diffraction, secondary ion mass spectroscopy, electron spin resonance, and magnetization measurements. Electron spin resonance studies demonstrate the existence of Fe in... (Read more)
- 517. 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)
- 518. Nature 442, 436 (2006) , “Atom-by-atom substitution of Mn in GaAs and visualization of their hole-mediated interactions”, D. Kitchen, A. Richardella, J. -M. Tang, M. E. Flatt, A. YazdaniThe discovery of ferromagnetism in Mn-doped GaAs1 has ignited interest in the development of semiconductor technologies based on electron spin and has led to several proof-of-concept spintronic devices2, 3, 4. A major hurdle for realistic applications of Ga1-XMnXAs, or other dilute magnetic semiconductors, remains that their ferromagnetic transition temperature is below room temperature. Enhancing ferromagnetism in semiconductors requires us to understand the mechanisms for interaction between magnetic dopants, such as Mn, and identify the circumstances in which ferromagnetic interactions are maximized5. Here we describe an atom-by-atom substitution technique using a scanning tunnelling microscope (STM) and apply it to perform a controlled study at the atomic scale of the interactions between isolated Mn acceptors, which are mediated by holes in GaAs. High-resolution STM measurements are used to visualize the GaAs electronic states that participate in the Mn–Mn interaction and to quantify the interaction strengths as a function of relative position and orientation. Our experimental findings, which can be explained using tight-binding model calculations, reveal a strong dependence of ferromagnetic interaction on crystallographic orientation. This anisotropic interaction can potentially be exploited by growing oriented Ga1-XMnXAs structures to enhance the ferromagnetic transition temperature beyond that achieved in randomly doped samples. (Read more)
- 519. 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)
- 520. 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)
- 521. Phys. Rev. B 74, 245219 (2006) , “Dynamics of positively charged muonium centers in indium nitride”, Y. G. Celebi, R. L. Lichti, B. E. Coss, and S. F. J. CoxMuon spin depolarization measurements performed on powdered InN with zero applied magnetic field reveal several positively charged diamagnetic muonium centers. At low temperatures, the Mu+ ground state is weakly relaxing with the characteristics of local tunneling motion, which changes to... (Read more)
- 522. Phys. Rev. B 74, 245217 (2006) , “Donor levels for selected n-type dopants in diamond: A computational study of the effect of supercell size”, J. P. Goss, P. R. Briddon, and R. J. EyreComputational techniques are key predictive tools in the drive to engineer semiconductive materials. Diamond, intrinsically a wide band-gap insulator, can be made to semiconduct n-type by doping with phosphorus. However, the relatively deep level at Ec−0.6 eV... (Read more)
- 523. 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)
- 524. Phys. Rev. B 74, 245212 (2006) , “Deactivation of nitrogen donors in silicon carbide”, F. Schmid, S. A. Reshanov, H. B. Weber, G. Pensl, M. Bockstedte, A. Mattausch, O. Pankratov, T. Ohshima, and H. ItohHexagonal SiC is either co-implanted with silicon (Si+), carbon (C+), or neon (Ne+) ions along with nitrogen (N+) ions or irradiated with electrons (e−) of 200 keV energy. During the subsequent annealing step at temperatures above 1450 ... (Read more)
- 525. Phys. Rev. B 74, 245205 (2006) , “Mn incorporation in as-grown and annealed (Ga,Mn)As layers studied by x-ray diffraction and standing-wave fluorescence”, V. Holý, Z. Matj, O. Pacherová, V. Novák, M. Cukr, K. Olejník, and T. JungwirthA combination of high-resolution x-ray diffraction and a technique of x-ray standing-wave fluorescence at grazing incidence is employed to study the structure of a (Ga,Mn)As-diluted magnetic semiconductor and its changes during post-growth annealing steps. We find that the film is formed by a... (Read more)
- 526. Phys. Rev. B 74, 245203 (2006) , “Diffusion and conversion dynamics for neutral muonium in aluminum nitride”, H. N. Bani-Salameh, R. L. Lichti, Y. G. Celebi, and S. F. J. CoxMuon spin depolarization rates and hyperfine decoupling curves imply the existence of a neutral muonium center to high temperatures in AlN, providing an experimental model for interstitial atomic hydrogen. This center has a hyperfine interaction close to that of the free atom, but with a small... (Read more)
- 527. Phys. Rev. B 74, 245201 (2006) , “Electrical resistivity and metal-nonmetal transition in n-type doped 4H-SiC”, Antonio Ferreira da Silva, Julien Pernot, Sylvie Contreras, Bo E. Sernelius, Clas Persson, and Jean CamasselThe electrical resistivity of 4H-SiC doped with nitrogen is analyzed in the temperature range 10–700 K for nitrogen concentrations between 3.5×1015 and 5×1019 cm−3. For the highest doped samples, a good agreement is found between the... (Read more)
- 528. 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)
- 529. Phys. Rev. B 74, 235434 (2006) , “Transport properties of n-type ultrananocrystalline diamond films”, I. S. Beloborodov, P. Zapol, D. M. Gruen, and L. A. CurtissWe investigate transport properties of ultrananocrystalline diamond films for a broad range of temperatures. Addition of nitrogen during plasma-assisted growth increases the conductivity of ultrananocrystalline diamond films by several orders of magnitude. We show that films produced at low... (Read more)
- 530. 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)
- 531. Phys. Rev. B 74, 235317 (2006) , “Impurity conduction in phosphorus-doped buried-channel silicon-on-insulator field-effect transistors at temperatures between 10 and 295 K”, Yukinori Ono, Jean-Francois Morizur, Katsuhiko Nishiguchi, Kei Takashina, Hiroshi Yamaguchi, Kazuma Hiratsuka, Seiji Horiguchi, Hiroshi Inokawa, and Yasuo TakahashiWe investigate transport in phosphorus-doped buried-channel metal-oxide-semiconductor field-effect transistors at temperatures between 10 and 295 K. We focus on transistors with phosphorus donor concentrations higher than those previously studied, where we expect conduction to rely on donor... (Read more)
- 532. 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)
- 533. Phys. Rev. B 74, 235214 (2006) , “Raman scattering study of H2 in Si”, M. Hiller, E. V. Lavrov, and J. WeberIsolated interstitial H2 and H2 bound to interstitial oxygen (O–H2) in single-crystalline Si are studied by Raman scattering. Two Raman signals at 3199(1) and 3193(1) cm−1 (T0 K) are identified as ro-vibrational transitions of... (Read more)
- 534. Phys. Rev. B 74, 235213 (2006) , “Mn 3d electronic configurations in (Ga1−xMnx)As ferromagnetic semiconductors and their influence on magnetic ordering”, F. Kronast, R. Ovsyannikov, A. Vollmer, H. A. Dürr, W. Eberhardt, P. Imperia, D. Schmitz, G. M. Schott, C. Ruester, C. Gould, G. Schmidt, K. Brunner, M. Sawicki, and L. W. MolenkampWe applied x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) at the Mn 2p-3d resonances to study the Mn 3d electronic configuration and the coupling of Mn 3d magnetic moments in various Ga1−xMnxAs films.... (Read more)
- 535. Phys. Rev. B 74, 235210 (2006) , “Dislocation-induced deep electronic states in InP: Photocapacitance measurements”, Yutaka Oyama, Jun-ichi Nishizawa, Toshihiro Kimura, and Takenori TannoPhotocapacitance and excitation photocapacitance methods were applied to reveal the dislocation-induced deep levels in coalescent epitaxial lateral overgrowth layers of InP. Point-contact Schottky barrier junctions with small junction areas were formed on dislocated and dislocation-free regions by... (Read more)
- 536. 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)
- 537. 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)
- 538. 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)
- 539. Phys. Rev. B 74, 235205 (2006) , “Optically-detected magnetic resonance of spin-paired complexes emitting in the 2.3 eV spectral region in Mg-doped GaN”, G. N. Aliev, S. Zeng, S. J. Bingham, D. Wolverson, J. J. Davies, T. Wang, and P. J. ParbrookOptically-detected magnetic resonance (ODMR) experiments on magnesium-doped GaN produced by metal-organic vapor phase epitaxy show a group of strong signals with large linewidths (in excess of 0.15 Tesla) obtained when monitoring photoluminescence in the region between 5000 Å and 6200 ... (Read more)
- 540. Phys. Rev. B 74, 235204 (2006) , “Bound excitons in Cu2O: Efficient internal free exciton detector”, J. I. Jang, Y. Sun, B. Watkins, and J. B. KettersonWe report the spectroscopic observation of bound excitons in natural Cu2O samples, which are generated by impurity capture of free excitons. Due to the broken symmetry of a bound exciton, its radiative recombination rate increases, causing a greatly enhanced luminescence intensity... (Read more)
- 541. 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)
- 542. Phys. Rev. B 74, 235104 (2006) , “Longitudinal and transverse diffusion of conduction-electron spins on stacks of fluoranthene radical cations”, David Saez de Jauregui, Jürgen Gmeiner, and Elmar DormannThe temperature dependence and anisotropy of the conduction-electron spin diffusion coefficient D(T) of three single crystals of the organic conductor (fluoranthene)2PF6 with defect content varying between 7×10−5 and 1% per formula unit have... (Read more)
- 543. Phys. Rev. B 74, 233203 (2006) , “Combined photoluminescence-imaging and deep-level transient spectroscopy of recombination processes at stacking faults in 4H-SiC”, A. Galeckas, A. Hallén, S. Majdi, J. Linnros, and P. PirouzWe report on electronic properties of single- and double-layer stacking faults in 4H-SiC and provide an insight into apparent distinctions of recombination-enhanced defect reactions at these faults. Photoluminescence imaging spectroscopy and deep-level transient spectroscopy experiments... (Read more)
- 544. 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)
- 545. Phys. Rev. B 74, 214409 (2006) , “Hyperfine interaction of Er3+ ions in Y2SiO5: An electron paramagnetic resonance spectroscopy study”, O. Guillot-Noël, Ph. Goldner, Y. Le Du, E. Baldit, P. Monnier, and K. BencheikhElectron paramagnetic resonance (EPR) spectroscopy of rare earth ions in crystals is a powerful tool to analyze the hyperfine structure of the rare earth ground state. This can be useful for coherent spectroscopy and quantum information applications where the hyperfine structure of the electronic... (Read more)
- 546. 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)
- 547. 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)
- 548. Phys. Rev. B 74, 205428 (2006) , “Er site in Er-implanted Si nanoclusters embedded in SiO2”, C. Maurizio, F. Iacona, F. D'Acapito, G. Franzò, and F. PrioloWe have investigated by extended x-ray absorption fine structure spectroscopy the local order around Er atoms introduced by ion implantation in substoichiometric silica films prepared by plasma enhanced chemical vapor deposition, where Si nanoclusters have been formed by different preimplantation... (Read more)
- 549. 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)
- 550. 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)
- 551. Phys. Rev. B 74, 205207 (2006) , “Charge-dependent migration pathways for the Ga vacancy in GaAs”, Fedwa El-Mellouhi, Norm, and MousseauUsing a combination of the local-basis ab initio program SIESTA and the activation-relaxation technique we study the diffusion mechanisms of the gallium vacancy in GaAs. Vacancies are found to diffuse to the second neighbor using two different mechanisms, as well as to the first and fourth... (Read more)
- 552. 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)
- 553. Phys. Rev. B 74, 195207 (2006) , “Magnetic phases and anisotropy in Gd-doped GaN”, L. Pérez, G. S. Lau, S. Dhar, O. Brandt, and K. H. PloogIn this work we present a detailed study of the magnetic properties of GaN:Gd layers with different Gd content (6×1015 to 1×1019 cm−3) grown by reactive molecular beam epitaxy. The temperature dependence of the magnetic properties suggests the... (Read more)
- 554. Phys. Rev. B 74, 195205 (2006) , “Magnetopolaron effect on shallow donors in GaN”, A. Wysmoek, R. Stpniewski, M. Potemski, B. Chwalisz-Pitka, K. Pakua, J. M. Baranowski, D. C. Look, S. S. Park, and K. Y. LeeResonant interaction between longitudinal-optic (LO) phonons and electrons bound on shallow donors in GaN is studied using magnetoluminescence of neutral-donor bound excitons (D0X). The experiments were performed on high-quality freestanding GaN material and heteroepitaxial... (Read more)
- 555. Phys. Rev. B 74, 195204 (2006) , “Interaction of iron with the local environment in SiGe alloys investigated with Laplace transform deep level spectroscopy”, Vl. Kolkovsky, A. Mesli, L. Dobaczewski, N. V. Abrosimov, Z. R. ytkiewicz, and A. R. PeakerLaplace transform deep level transient spectroscopy (LDLTS) is used to investigate the alloy effects on iron related deep centers in Si1−xGex. A clear buildup of alloy disorder as a function of the germanium content has been observed for the isolated... (Read more)
- 556. 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)
- 557. Phys. Rev. B 74, 195128 (2006) , “First-principles calculations of native defects in tin monoxide”, A. Togo, F. Oba, I. Tanaka, and K. TatsumiThe formation energies and electronic structure of native defects in tin monoxide are investigated by first-principles calculations. Equilibrium defect concentrations, which are obtained using the calculated formation energies and charge neutrality, indicate that the tin vacancy is the dominant... (Read more)
- 558. Phys. Rev. B 74, 195101 (2006) , “Characterization of the hyperfine interaction in europium-doped yttrium orthosilicate and europium chloride hexahydrate”, J. J. Longdell, A. L. Alexander, and M. J. SellarsWe present characterization of the hyperfine interaction for the europium in hydrated europium chloride and as a dopant in yttrium orthosilicate. The Zeeman and pseudoquadrupole tensors were determined by measuring the hyperfine splittings while rotating the direction of a weak (~300 G) magnetic... (Read more)
- 559. 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)
- 560. 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)
- 561. 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)
- 562. 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)
- 563. Phys. Rev. B 74, 174206 (2006) , “Nuclear quadrupole resonance study of local bonding in glassy AsxSe1−x”, Eungho Ahn, G. A. Williams, and P. C. TaylorNuclear quadrupole resonance (NQR) experiments were performed on glassy AsxSe1−x to study the local structural order. The bonding in AsxSe1−x is governed by preferential bonding (chemical ordering) between arsenic... (Read more)
- 564. Phys. Rev. B 74, 174122 (2006) , “Lithium colloids and color center creation in electron-irradiated Li2NH observed by electron-spin resonance”, F. Beuneu, P. Vajda, Y. Nakamori, and S. OrimoWe have irradiated Li2NH powder with MeV electrons at room temperature and investigated the introduced defects with electron spin resonance. Conduction electron spin resonance indicates the presence of nanosize metallic Li colloids seen as a Lorentzian line with a g=2.0023 and a... (Read more)
- 565. Phys. Rev. B 74, 174120 (2006) , “Single-crystal silicon coimplanted by helium and hydrogen: Evolution of decorated vacancylike defects with thermal treatments”, C. Macchi, S. Mariazzi, G. P. Karwasz, R. S. Brusa, P. Folegati, S. Frabboni, and G. OttavianiSi p-type (100) samples were coimplanted at room temperature with He+ ions at 30 keV with a dose of 1×1016 ions/cm2 and successively with H+ ions at 24 keV with a dose of 1×1016 ions/cm2. A series of samples was... (Read more)
- 566. 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)
- 567. 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)
- 568. 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)
- 569. Phys. Rev. B 74, 165204 (2006) , “Electronic structure of rare-earth impurities in GaAs and GaN”, A. Svane, N. E. Christensen, L. Petit, Z. Szotek, and W. M. TemmermanThe electronic structures of substitutional rare-earth (RE) impurities in GaAs and cubic GaN are calculated. The total energy is evaluated with the self-interaction corrected local spin density approximation, by which several configurations of the open 4f shell of the rare-earth ion are... (Read more)
- 570. Phys. Rev. B 74, 165203 (2006) , “Isotopic-mass dependence of the A, B, and C excitonic band gaps in ZnO at low temperatures”, S. Tsoi, X. Lu, A. K. Ramdas, H. Alawadhi, M. Grimsditch, M. Cardona, and R. LauckLow temperature wavelength-modulated reflectivity measurements of isotopically engineered ZnO samples have yielded the dependence of their A, B, and C excitonic band gaps on the isotopic masses of Zn and O. The observed dependence is analyzed in terms of the band gap renormalization by zero-point... (Read more)
- 571. Phys. Rev. B 74, 165202 (2006) , “Structural and electronic properties of Fe3+ and Fe2+ centers in GaN from optical and EPR experiments”, E. Malguth, A. Hoffmann, W. Gehlhoff, O. Gelhausen, M. R. Phillips, and X. XuThis work provides a consistent picture of the structural, optical, and electronic properties of Fe-doped GaN. A set of high-quality GaN crystals doped with Fe at concentrations ranging from 5×1017 cm3 to 2×1020 cm3 is... (Read more)
- 572. Phys. Rev. B 74, 165201 (2006) , “Internal 5E ? 5T2 transition of Fe2+ in GaN”, E. Malguth, A. Hoffmann, and X. XuWe present Fourier transform infrared transmission measurements on Fe-doped GaN. A set of freestanding high-quality GaN:Fe samples with varying Fe concentrations shows a rich absorption structure around 390 meV which is unambiguously assigned to the internal... (Read more)
- 573. Phys. Rev. B 74, 165116 (2006) , “Density-functional-theory calculations for the silicon vacancy”, A. F. WrightThe atomic configurations and formation energies of a silicon vacancy in the +2, +1, 0, −1, and −2 charge states have been computed using density-functional theory with norm-conserving pseudopotentials and a plane wave basis. Calculations were performed in simple cubic supercells using... (Read more)
- 574. Phys. Rev. B 74, 161203(R) (2006) , “Room-temperature manipulation and decoherence of a single spin in diamond”, R. Hanson, O. Gywat, and D. D. AwschalomWe report on room-temperature coherent manipulation of the spin of a single nitrogen-vacancy center in diamond and a study of its coherence as a function of magnetic field. We use magnetic resonance to induce Rabi nutations and apply a Hahn spin echo to remove the effect of low-frequency dephasing.... (Read more)
- 575. Phys. Rev. B 74, 161202 (2006) , “Deactivation of Li by vacancy clusters in ion-implanted and flash-annealed ZnO”, T. Moe Børseth, F. Tuomisto, J. S. Christensen, W. Skorupa, E. V. Monakhov, B. G. Svensson, and A. Yu. KuznetsovLi is present in hydrothermally grown ZnO at high concentrations and is known to compensate both n- and p-type doping due to its amphoteric nature. However, Li can be manipulated by annealing and ion implantation in ZnO. Fast, 20 ms flash anneals in the 9001400 °C range... (Read more)
- 576. Phys. Rev. B 74, 161201 (2006) , “Detection of magnetic resonance of donor-bound electrons in GaAs by Kerr rotation”, T. A. Kennedy, J. Whitaker, A. Shabaev, A. S. Bracker, and D. GammonMagnetic resonance of electrons in lightly doped GaAs layers has been detected at 5.8 T by magneto-optical Kerr rotation. A study over a wide range of microwave powers shows (1) resonance without dynamic nuclear polarization (DNP), (2) resonance enhanced by DNP, and (3) DNP pinning of the resonance... (Read more)
- 577. Phys. Rev. B 74, 155429 (2006) , “Effect of nitrogen on the electronic properties of ultrananocrystalline diamond thin films grown on quartz and diamond substrates”, P. Achatz, O. A. Williams, P. Bruno, D. M. Gruen, J. A. Garrido, and M. StutzmannThe electronic transport properties of ultrananocrystalline diamond thin films grown from an argon-rich Ar/CH4 microwave plasma have been investigated in the temperature range from 300 up to 700 K and as a function of nitrogen added to the gas phase (from 0 to 20%). The influence of... (Read more)
- 578. Phys. Rev. B 74, 155425 (2006) , “Ab initio study of native defects in SiC nanotubes”, R. J. Baierle, P. Piquini, L. P. Neves, and R. H. MiwaSpin-polarized density functional theory is used to investigate the electronic and structural properties of vacancies and antisites in zigzag, armchair, and chiral SiC nanotubes. Antisites present lower formation energies compared to vacancies, introducing an empty electronic level close to the... (Read more)
- 579. Phys. Rev. B 74, 155310 (2006) , “Optical study of excitation and deexcitation of Tm in GaN quantum dots”, Thomas Andreev, Nguyen Quang Liem, Yuji Hori, Mitsuhiro Tanaka, Osamu Oda, Daniel Le Si Dang, Bruno Daudin, and Bruno GayralWe report on the optical properties of molecular beam epitaxy grown GaN quantum dots (QDs) doped with Tm. Under optical excitation above the fundamental energy of GaN QDs, the fundamental transition emission from the GaN QD host was not observed while bright emission from Tm3+ manifolds... (Read more)
- 580. 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)
- 581. Phys. Rev. B 74, 155205 (2006) , “Ab initio studies of the electronic structure of defects in PbTe”, Salameh Ahmad, S. D. Mahanti, Khang Hoang, and M. G. KanatzidisUnderstanding the detailed electronic structure of deep defect states in narrow band-gap semiconductors has been a challenging problem. Recently, self-consistent ab initio calculations within density functional theory using supercell models have been successful in tackling this problem. In... (Read more)
- 582. Phys. Rev. B 74, 155204 (2006) , “Vibronic spectrum of c-BN measured with cathodoluminescence”, C. Manfredotti, R. Cossio, A. Lo Giudice, E. Vittone, and F. FizzottiAn extended vibronic spectrum (up to six phonon replicas) has been measured by low temperature cathodoluminescence in pure c-BN microcrystalline samples obtained by high temperature high pressure method. The zero phonon line, found at 3.573 eV, should be connected to a center identified... (Read more)
- 583. Phys. Rev. B 74, 155203 (2006) , “Antisite effect on hole-mediated ferromagnetism in (Ga,Mn)As”, R. C. Myers, B. L. Sheu, A. W. Jackson, A. C. Gossard, P. Schiffer, N. Samarth, and D. D. AwschalomWe study the Curie temperature and hole density of (Ga,Mn)As while systematically varying the As-antisite density. Hole compensation by As-antisites limits the Curie temperature and can completely quench long-range ferromagnetic order in the low doping regime of 1%2% Mn. Samples are grown by... (Read more)
- 584. 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)
- 585. 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)
- 586. Phys. Rev. B 74, 153311 (2006) , “Electron transport in laterally confined phosphorus δ layers in silicon”, S. J. Robinson, J. S. Kline, H. J. Wheelwright, J. R. Tucker, C. L. Yang, R. R. Du, B. E. Volland, I. W. Rangelow, and T.-C. ShenTwo-dimensional electron systems fabricated from a single layer of P-donors have been lithographically confined to nanometer scale in lateral directions. The electronic transport of such quasi-one-dimensional systems with and without a perpendicular magnetic field was characterized at cryogenic... (Read more)
- 587. Phys. Rev. B 74, 153201 (2006) , “Light-induced hyperfine 69Ga shifts in semi-insulating GaAs observed by optically polarized NMR”, Kannan Ramaswamy, Stacy Mui, and Sophia E. HayesWe report the observation of 69Ga NMR light induced hyperfine shifts at 6 K in semi-insulating GaAs detected by optically polarized nuclear magnetic resonance in a magnetic field of 4.7 T. The main features of the observed shift are a systematic change in the absolute shift value as the... (Read more)
- 588. Phys. Rev. B 74, 144432 (2006) , “Role of defects in ferromagnetism in Zn1−xCoxO: A hybrid density-functional study”, C. H. PattersonExperimental studies of Zn1−xCoxO as thin films or nanocrystals have found ferromagnetism and Curie temperatures above room temperature and that p- or n-type doping of Zn1−xCoxO can change its magnetic... (Read more)
- 589. Phys. Rev. B 74, 144106 (2006) , “Density functional theory calculation of the DI optical center in SiC”, T. A. G. Eberlein, R. Jones, S. Öberg, and P. R. BriddonThe DI center is a prominent defect which is detected in as-grown or irradiated SiC. It is unusual in that its intensity grows with heat treatments and survives anneals of 1700 °C. It has been assigned recently to either a close-by antisite pair or to the close-by antisite... (Read more)
- 590. Phys. Rev. B 74, 140502(R) (2006) , “Lattice parameters and thermal expansion of superconducting boron-doped diamonds”, V. V. Brazhkin, E. A. Ekimov, A. G. Lyapin, S. V. Popova, A. V. Rakhmanina, S. M. Stishov, V. M. Lebedev, Y. Katayama, and K. KatoUsing two different high-pressure techniques, we have prepared boron-doped diamonds with atomic concentration of the dopant ranging from 0.04% to 4% (from 7×1019 to 7×1021 atom/cm3) and studied the lattice constants and thermal expansion of the diamonds... (Read more)
- 591. Phys. Rev. B 74, 134418 (2006) , “Electron spin resonance and its implication on the maximum nuclear polarization of deuterated solid target materials”, J. Heckmann, W. Meyer, E. Radtke, G. Reicherz, and S. GoertzESR spectroscopy is an important tool in polarized solid target material research, since it allows us to study the paramagnetic centers, which are used for the dynamic nuclear polarization (DNP). The polarization behavior of the different target materials is strongly affected by the properties of... (Read more)
- 592. Phys. Rev. B 74, 134303 (2006) , “1H NMR study of proton dynamics in Cs5H3(SO4)4·xH2O”, Koh-ichi Suzuki and Shigenobu HayashiComplicated phase relations in Cs5H3(SO4)4·xH2O are revealed by thermal analyses. A superprotonic phase transition takes place at 420 K for both the hydrated and the anhydrous forms. The 1H magic-angle-spinning (MAS) NMR... (Read more)
- 593. Phys. Rev. B 74, 134102 (2006) , “Phosphorous–oxygen hole centers in phosphosilicate glass films”, M. Fanciulli, E. Bonera, S. Nokhrin, and G. PacchioniPhosphosilicate glass films produced by subatmospheric pressure chemical vapor deposition with different phosphorus concentrations have been investigated by ultraviolet Raman spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. The behavior and the attribution of the main Raman band... (Read more)
- 594. Phys. Rev. B 74, 132107 (2006) , “Evidence of extended defects in pure zirconia irradiated by swift heavy ions”, Gianguido Baldinozzi, David Simeone, Dominique Gosset, Isabelle Monnet, Sophie Le Caër, and Léo MazerollesX-ray diffraction, transmission electron microscopy, and optical spectroscopy were used to investigate the microstructure of polycrystalline samples of pure monoclinic zirconia irradiated by high energy ions. These techniques point out the existence of extended defects and they allow to monitor the... (Read more)
- 595. Phys. Rev. B 74, 125203 (2006) , “Density functional theory of structural transformations of oxygen-deficient centers in amorphous silica during hole trapping: Structure and formation mechanism of the Egamma[prime]" align="middle"> center”, T. Uchino and T. YokoWe investigate the hole trapping process of a neutral oxygen vacancy in amorphous silicon dioxide (a-SiO2) using cluster calculations based on the density functional theory (DFT) method. We show that trapping a hole at a neutral oxygen vacancy leads to the formation of several... (Read more)
- 596. Phys. Rev. B 74, 121201 (2006) , “Prediction of the anomalous fluorine-silicon interstitial pair diffusion in crystalline silicon”, Scott A. Harrison, Thomas F. Edgar, and Gyeong S. HwangWe propose a diffusion pathway for a fluorine-silicon interstitial pair (F-Sii) in silicon based on extensive first-principles density functional calculations. We find the F-Sii pair to be most stable in the singly positive charge state under intrinsic conditions and can exist... (Read more)
- 597. Phys. Rev. B 74, 115203 (2006) , “From ferromagnetic to antiferromagnetic interactions in n-type Zn1–xMnxO: An electron paramagnetic resonance study”, A. Ben Mahmoud, H. J. von Bardeleben, J. L. Cantin, A. Mauger, E. Chikoidze, and Y. DumontContradictory results concerning the formation of a ferromagnetic state in Mn doped ZnO layers have been reported in the last years. We present the results of an electron paramagnetic resonance study on homogeneous single phase n-type conductive Zn1xMnxO... (Read more)
- 598. Phys. Rev. B 74, 115201 (2006) , “Magnetic circular dichroism spectra in a II-VI diluted magnetic semiconductor Zn1–xCrxTe: First-principles calculations”, Hongming Weng, Jinming Dong, Tomoteru Fukumura, Masashi Kawasaki, and Yoshiyuki KawazoeThe absorption and magnetic circular dichroism (MCD) spectra of Zn1xCrxTe for x=0.0625, 0.25, and 1.0 are studied using the first-principles method. The calculated MCD spectra are found to be well consistent with the experimental measurement at the... (Read more)
- 599. Phys. Rev. B 74, 115118 (2006) , “Optical properties of Cr3+ –doped oxides: Different behavior of two centers in alexandrite”, J. M. García-Lastra, J. A. Aramburu, M. T. Barriuso, and M. MorenoThis work is aimed at explaining the different color exhibited by the two Cr3+ centers in the alexandrite gemstone as well as ruby and emerald. Although the average Cr3+-O2 distance in ruby, emerald, and the Cs center in alexandrite is known... (Read more)
- 600. 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)
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