bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman Scattering Characterization of Bonding Defects in Silicon
Authors: Tsu Raphael 
Published: March 2011

ABSTRACTRaman scattering is used for the characterization of defects in Si. Damage is produced in single crystal silicon by ion-implantation of As and Si. The phonon structure of the damaged layer is that of the typical amorphous Si. After irradiation by pulsed laser(10ns,532nm) at energy density of approximately 0.1J/cm2, a Raman peak appears at a frequency between 508 cm−1 and 517 cm−1 depending on implant dosage. The higher the implant dosage, the lower is the frequency. We explain this in terms of the residual bonding defects caused by the presence of extraneous atoms such as oxygen. On the other hand, irradiation at an energy density in excess of 0.5 J/cm2, a Raman peak appears at a frequency close to that of the single crystal except for small shifts due to Fano-shift. For implant dosage in excess of 4×1016 As/cm2 , we have found additional peaks at 222 cm−1 and 267 cm−1 which are close to the metallic arsenic modes indicating the presence of arsenic clusters.
Luminescence Properties of GaAs Epitaxial Layers Grown By Liquid Phase Epitaxy and Molecular Beam Epitaxy
Authors: Petroff P. M. 
Published: March 2011

ABSTRACTThe luminescence properties of undoped GaAs-Ga1−x Alx As layers grown by liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE) are compared for double heterostructure and multiquantum well (MQW) superlattices. Low temperature cathodoluminescence and scanning transmission electron microscopy are used to identify the main luminescence centers and in some instances establish their origin. The possible effects of the observed luminescence features on the degradation process in GaAs-Gal−x Alx As laser devices grown by MBE and LPE are also discussed.
The Interrelationship Between Structure and Properties in InP and InGaAsP Materials
Authors: Mahajan S. 
Published: March 2011

ABSTRACTThree examples pertaining to the influence of heavy doping on the microscopic perfection of as-grown InP crystals, thermal decomposition of InP crystals and epi-layers and optically induced degradation of InGaAsP epi-layers have been chosen to delineate some of the correlations observed between microstructure and properties in these materials. It
is shown that the macroscopic perfection can be significantly improved by highly doping with Zn, S, and Se. However, in the case of Zn, not all of the dopant atoms are in solid solution and some of them have clustered to form precipitates, whereas these features are not seen in highly S- and Se-doped crystals.Thermal decomposition of epi-layers introduces areas which appear dark in a photoluminescence scan. It is argued that these regions evolve due to the out diffusion of P. In addition, when InP epi-layers are grown on thermally-decomposed substrates, dislocation density in the epi-layers is higher than that in the substrate. Arguments have been developed to rationalize these observations.Non-luminescent regions develop in InGaAsP epilayers by optical pumping. These areas are associated with dislocation clusters which appear to evolve by glide of the existing dislocations.
Electronic Defects in Metalorganic GaAIAs
Authors: Johnson N. M. , Burnham R. D. , Fekete D. , Yingling R. D. 
Published: March 2011

ABSTRACTElectronic defect levels have been measured in n-type epitaxial films of Gal - XAIXAs (0≤X≤0.33) which were grown by metalorganic chemical vapor deposition. Electron traps were characterized by transient capacitance spectroscopy on Schottky-barrier diodes. The thermal activation energy for electron emission from the near-midgap defect level is found to be larger in Ga1 - XAIXAs than the value of 0.83 eV generally observed in GaAs.
Tem and Sem Studies of Defects in Gainas and Gainasp Epitaxial-Layer Device-Type Structures
Authors: Al-Jassim M.M. , Hockly M. , Booker G.R. 
Published: March 2011

ABSTRACTTEM and SEM studies have been carried out on a series of GaAs/GaInAs, InP/GaInAs and InP/GaInAsP device-type structures grown either by vapour phase epitaxy (VPE) or liquid phase epitaxy (LPE). By using the TEM high voltage electron microscope operating at 1000kV, a determination was made of the nature, origin and three-dimensional distribution of structural defects in these specimens (mainly dislocations and stacking faults). SEM EBIC and CL examinations were also performed to study the electrical and luminescent properties of these layers. The ultimate aim is to correlate structural information with electrical and luminescent properties, and with device performance.
Microstructure of Polycrystalline Sic Containing Excess Si after Neutron Irradiation
Authors: Harrison S.D. , Corelli J.C. 
Published: March 2011

ABSTRACTThe microstructure of commercially available reactionbonded polycrystalline SiC containing 8–10 wt% excess silicon was studied after irradiation by reactor neutrons uitlizing transmission electron microscopy (TEM) and scanning electron microscopy (SEM). For TEM studies on samples irradiated below 473°K we observe dislocation tangles near grain boundaries or impurities plus isolated dislocations throughout the remainder of the grain, whereas for irradiation temperatures of ≈3730°K the material exhibits copious quantities of “black spot” defects (2–5nm size) and a lower concentration of tangles than 473°K irradiation. The SEM studies of surfaces of samples fractured at 1473°K indicate that the mode of fracture is predominantly transgranular.
Point Defects, Diffusion Mechanisms, and the Shrinkage and Growth of Extended Defects in Silicon
Authors: Gösele Ulrich , Frank Werner 
Published: March 2011

ABSTRACTThe paper introduces the basic point-defect models proposed for silicon, which involve either vacancies or self-interstitials only, or both types of point defects simultaneously under thermal-equilibrium conditions. The growth and shrinkage kinetics of oxidation-induced stacking faults as well as oxidation-enhanced or -retarded diffusion phenomena are discussed within the frame work of these models. Whereas no unambiguous conclusions on the dominant diffusion mechanism can be drawn from the available oxidation-related experiments, recent investigations on so-called anomalous diffusion phenomena (e.g., the ‘emitter-push effect’) and on the diffusion of gold in silicon demonstrate Si self-interstitials to be the point defects governing self- and impurity diffusion. The possibility of a coexistence of vacancies and self-interstitials in thermal equilibrium is discussed in this context. The paper concludes with speculations on how carbon in conjunction with self-interstitials may influence the nucleation process of oxygen precipitates in silicon.
Processing Effects on the Electrical and Optical Properties of Sulfur-Related Defect Centers in Silicon and Similarities to the Oxygen Donor
Authors: Forman Richard A. , Larrabee Robert D. , Myers David R. , Phillips Willie E. , Thurber W. Robert 
Published: March 2011

ABSTRACTThe properties of sulfur-related defects in silicon are shown to differ dramatically from those that would have been expected on the basis of effective mass theory for a simple substitutional double donor. The ratio of the densities of the sulfur states as measured by capacitance-voltage techniques has been observed to vary in specimens fabricated from the same starting resistivity. Optical absorption studies have shown that the deepest sulfur level has a manifold of ground states which anneal at unequal rates at 550°C. Deep-level measurements show that the thermal emission rate at a given temperature and the variety of effects produced depends on annealing history and total sulfur density. The variability of properties of samples of sulfur-doped silicon is similar to those found for the oxygen donors in silicon, thus suggesting a chemical trend for the column VI impurities in silicon.
Defect Characterization by Junction Spectroscopy
Authors: Kimerling L. C. 
Published: March 2011

ABSTRACTJunction spectroscopic techniques provide a unique tool for the study of imperfections in semiconductor materials. New, fundamental defect processes have been discovered and direct observations of the role of defects in device manufacture and operation have been made. The principles of application of capacitance transient spectroscopy, electroluminescence, and SEM-charge collection microscopy are briefly reviewed. Examples of singular accomplishments of these techniques are given, and directions of future research are outlined.
Free-Electron Interlayer States in Pure and Li-Intercalated Graphite
Authors: Posternak M. , Baldereschi A. , Freeman A.J. , Wimmer E. , Weinert M. 
Published: March 2011

ABSTRACTFirst–principle SCF–FLAPW calculations prove the existence in graphite of a new kind of electron states. They are interlayer states, resulting from the bonding combination of states bound to single graphite layers, and give rise to a still undetected energy band just above the Fermi energy. This band also occurs at slightly lower energy in Li intercalated graphite, and has been incorrectly interpreted as arising mainly from Li 2s orbitals.
Superconductivity in Graphite Intercalation Compounds
Authors: Iye Yasuhiro 
Published: March 2011

ABSTRACTSuperconductivity in graphite intercalation compounds, C4nMHg (M:K, Rb, n=1,2) and C4KTl1.5 is studied in ambient as well as elevated pressures. It is argued that the major role in the superconductivity of this class of materials is played by electrons in the intercalant bands rather than those in the graphite bands. It is experimentally demonstrated that the two-dimensional anisotropy of the superconductivity is controlled by stage and pressure.
Anomalous Pressure Dependences of the Superconducting Transition Temperature of Graphite Intercalation Compounds
Authors: Delong L.E. , Yeh V. , Tondiglia V. , Eklund P.C. , Lambert S.E. , Maple M.B. 
Published: March 2011

ABSTRACTMeasurements of the pressure (P) dependence of the superconducting transition temperature Tc of KHgC4, KHgC8, KTℓ1.5C4 and KC8 are reported. KC24 was found to be nonsuperconducting to a limiting temperature T ≈ 0.07 K for P ≤ 10 kbar, and RbC8 was found to be nonsuperconducting to T ≈ 1.30 K for P ≤ 22 kbar. The Tc of KHgC8 was found to monotonically decrease at a rate dTc/dP = −6.5 × 10−5 K/bar from a zero pressure Tc = 1.850 K. The Tc of KTℓ1.5C4 initially decreases at a rate dTc/dP≤ −4.5 × 10−5 K/bar from a zero pressure Tc = 2.54 K. KHgC4 displayed a broad zero pressure superconducting transition with an onset at T ≈ 1.42 K, followed by an abrupt narrowing of the transition and rapid decrease of Tc at a rate dTc/dP = −5 × 10−5 K/bar at p > 1 kbar. The Tc of KC8 was observed to jump from a zero pressure value of 0.13 K to a broad transition with an onset at ˜ 1.7 K for P > 2 kbar.
Commensurate-Incommensurate and Melting Transitions in Bromine-Intercalated Single Crystal Kish Graphite
Authors: Erbil A. , Kortan A.R. , Birgeneau R.J. , Dresselhaus M.S. 
Published: March 2011

ABSTRACTWe summarize the results of an extensive x-ray scattering study of the phase transitions in intercalated graphite-Br2 compounds. The experiments are aimed at understanding the intraplanar and interplanar correlations of the intercalate bromine as a function of temperature. Using in-situ high resolution x-ray scattering techniques, we have studied stage-4 graphite-Br2 under equilibrium conditions, where the intercalant is in the commensurate phase, incommensurate phase, and fluid phase. We demonstrate that the transitions between these phases are model examples of phase transitions in quasi two-dimensional systems. The coherently ordered in-plane bromine regions exceed 10000 Å in size in both commensurate and incommensurate phases. A commensurateincommensurate transition in the 7–fold direction is observed from a centered (√3 × 7) phase to a stripe domain phase. The domain wall density exhibits a power-law behavior in temperature with an exponent of 0.50 ± 0.02. We have also observed power-law lineshapes for bromine superlattice peaks in the incommensurate phase due to the rigorous absence of true long range order. The intercalate layer appears to exhibit an anisotropic melting transition from an incommensurate solid to a novel fluid phase.
Phonon Dispersion of Transverse Basal Plane Modes in Alkali-Graphite Compounds
Authors: Kamitakahara W. A. , Zabel H. , Nicklow R. M. 
Published: March 2011

ABSTRACTDispersion curves for low-frequency transverse modes propagating in the basal plane have been measured in the compounds KC8, KC24 and RbC24 by means of neutron inelastic scattering. The acoustic branches show at low q a behavior ω2= Aq2+Bq4 characteristic of layered materials. The optical branches are derived qualitatively from graphite-like optical branches hybridized with new alkali-like branches. In stage 2 compounds, the shear constant C44, which can be obtained by extrapolating the acoustic branch towards q=0, is appreciably smaller than in stage-1 compounds or in pure graphite. At low temperatures, it was noted in KC24 that a frequency gap in the acoustic branch opens up near q=0.6 A-1, corresponding to the Brillouin zone boundary of the low temperature alkali superstructure.
Intercalate Phonon Densities of States for Alkali-Graphite Compounds
Authors: Kamitakahara W. A. , Zabel H. 
Published: March 2011

ABSTRACTNeutron scattering methods have been used to determine the partial phonon densities of states gM(ν) for inplane vibrations of M atoms in MCx compounds, where M = K, Rb or Cs, and x = 8, 24, 36. Only modes with both phonon wave vectors and displacements in the basal plane are represented in gM(ν). Detailed measurements of the temperature dependence were made for RbC24 and KC24, in order to study the influence of the order-disorder transformations in these compounds. The results are interpreted in terms of different pictures of the disordered state.
Populations of Fluorine and Arsenic in AsF5-Graphite Intercalation Compounds
Authors: Sfihi H. , Facchini L. , Bouat J. , Bonnin D. , Legrand A.P. , Furdin G. , Billaud D. 
Published: March 2011

ABSTRACT19F nuclear magnetic resonance and As X-ray absorption results on AsF5-graphite intercalation compounds are discussed in terms of species of the commonly used oxidation reaction of the graphitic planes. Three fluorine populations and two oxidation states of the arsenic are clearly present, but they cannot be easily related to the oxidation reaction of the graphite planes.
57Fe Mössbauer Spectroscopic Study of the Geometrical Effects In the Catalytic Reactions with Intercalation Compounds
Authors: Vaishnava P.P. , Montano P.A. 
Published: March 2011

ABSTRACTIn situ 57Fe Mössbauer spectra are reported for the first-, higher-stage ferric chloride, and a mixed ferric chloride-potassium chloride intercalated graphite catalysts under reduction and Fischer-Tropsch reaction conditions. The mass spectroscopic measurements reveal a different catalytic selectivity for the three catalysts. The first two catalysts predominantly possess a higher selectivity for methane, whereas the third catalyst has higher selectivity for the formation of propane. The differences are attributed to geometrical effects in the catalytic sites of the intercalated compounds.
Study of the Orientation of Molecules Intercalated in Graphite using Nuclear Photon Scattering
Authors: Moreh Raymond , Shahal Oded 
Published: March 2011

ABSTRACTA new technique utilizing nuclear resonance scattering of photons from isolated nuclear levels in the 6-9 MeV range is being used for studying the orientation of certain intercalant molecules with respect to the graphite (G) planes. This technique may be applied to intercalants containing 11B, 15N, 39K, 48Ti, 50Cr, 56Fe, 62Ni and 68Zn. As an example, the orientation of the HNO3 molecules intercalated in HOPG was studied by photon scattering from the 6.324 MeV level in 15N. Thus in C10 (HNO3) and C15(HNO3), the NO3 planes were found to be oriented at θ ˜ 90° relative to the G planes, while in the mixture of the ‘residue’ compounds C16(HNO3) and C24(HNO3), the NO3 planes were found to be nearly parallel, θ0 < 25°, relative to the G-planes.
Basic Thin Film Process for Perovskite Ferroelectric Materials
Authors: Adachi Hideaki , Wasa Kiyotaka 
Published: March 2011

ABSTRACTThin film process for ferroelectric perovskite oxides has been investigated. Amorphous, polycrystal, and epitaxial thin films of Pb-based perovskite ferroelectrics were prepared by rf-magnetron sputtering, and their properties were discussed. Epitaxial PLZT thin films showed similar dielectric properties as PLZT bulk ceramics and also showed strong electrooptic effect. For further investigation, film preparation process was developed by multitarget sputtering and quaternary PLZT thin film with excellent epitaxial crystallinity was realized by using a graded composition layer.
Ferroelectric Thin Films Deposited by Laser Ablation
Authors: Ramkumar K. , Lee J. , Safari A. , Danforth S.C. 
Published: March 2011

ABSTRACTThe deposition of thin films of ferroelectric materials by the laser ablation technique was investigated. The films were grown by ablation from a bulk target of lead zirconate titanate (PZT) exposed to laser pulses from CO2 amd KrF excimer lasers. The effects of deposition and annealing conditions on the structure and stoichiometry of the films were studied.
Processing Induced Strain Relaxation in BaTiO3 Films
Authors: Sanchez-Carambot E. , Martinez-Miranda L.J. , Smela E. , Shi Y. , Santlago-Aviles J.J. 
Published: March 2011

ABSTRACTThe development of integrated electronic devices has resulted in an increased interest in the study of ferroelectric ceramic films on silicon prepared by diverse methods. Some of these studies aim at the development of films whose ferroelectric properties equal or approximate those of the bulk ceramic. It is therefore important to attain a better understanding of the microstructure of these films and the relationship between the microstructure and the different film preparation methods. This study examines the strain field in such a film as a function of annealing time. The technique chosen was grazing incidence x-ray scattering (GIXS), and the material, thin films of BaTiO3 deposited on silicon (111) single crystals by metallo-organic deposition (MOD). The BaTiO3 {110} and {101} reflections were monitored. A substantial relaxation of the d-spacing of planes parallel to the surface was measured after a 64 hour annealing. The d-spacing of planes perpendicular to the surface remained essentially unchanged.
Ten Analyses Of Sol-Gel Derived And Sputtered PZT Thin Films
Authors: Hsueh Cheng-Chen , MeCartney Martha L. 
Published: March 2011

ABSTRACTFerroelectric PZT thin films were prepared by sol-gel methods and RF magnetron sputtering. Sputtered PZT fast fired at 650° for 30 minutes showed microporosity. For the sol-gel route, solution precursors had a significant effect on the microstructure of the crystalline PZT films. PZT thin films derived from metal-organic precursors dissolved in n-propanol were observed to have large and microporous spherulitic grains on the order of 2 μm and phase separation in acetic acid-catalyzed films. In contrast, PZT precursors originated from alcohol exchanges with 2-methoxyethanols resulted in dense films with fine grains of ∼0.2 μm and clear evidence of ferroelectric domains. The dense sol-gel films possessed superior dielectric and ferroelectric properties.
Electro-Optic and Non-Linear Optical Coefficients of (Pb, La)(Zr, Ti)O3, BaTiO3, (Sr, Ba)Nb2O6 and Ba2NaNb5O15 Thin Films
Authors: Wu A. Y. , Wang Feiling , Juang Ching-Bo , Bustamante Carlos 
Published: March 2011

ABSTRACTThe electro-optic properties of sputter-deposited PLZT, BaTiO3, SBN, and BNN films on fused silica substrates have been studied using a confocal scanning optical polarization microscope. The Pockels, Kerr, and higher order electro-optic coefficients and their relations to the non-linear optical coefficients in the films are presented. The materials and physical properties of the films are discussed.
Characterization of Ferroelectric Thin Films by ESCA
Authors: Desu Seshu B. , Kwok Chi K. 
Published: March 2011

ABSTRACTElectron spectroscopy for chemical analysis (ESCA) is well suited for investigating the surfaces of ferroelectric films. More importantly, this technique is valuable for ferroelectric films because, reduction of ions, such as Pb2+, Bi3+, and Ti4+ by photon beam is much less likely than probing electron and ion beams which are used in other methods. In the present paper a brief description of the possibilities of ESCA for determining qualitative and quantitative surface composition, and thickness of extremely thin films was presented. Special emphasis was given to multicomponent films, such as lead zirconate titanate (PZT). Factors that lead to considerable difference in the composition of the surface were discussed. Different depth profiling techniques using ESCA were also presented.
Scaling Properties in the Electrical and Reliability Characteristics of Lead-Zirconate-Titanate (PZT) Ferroelectric Thin Film Capacitors
Authors: Sudhama C. , Carrano J. C. , Parker L. H. , Chikarmane V. , Lee J. C. , Tasch A. F. , Miller W. , Abt N. , Shepherd W. H. 
Published: March 2011

ABSTRACTThis paper investigates the issues in the scaling of thin film PZT (Lead-Zirconate-Titanate) capacitors for DRAM (Dynamic Random Access Memories) applications. The test structures used were MIM (metal-insulator-metal) capacitors with platinum electrodes and PZT deposited using a sol-gel process. Charge storage density (Q'c), leakage current density (JL), unipolar switching time to 10% decay (ts), time dependent dielectric breakdown (TDDB) and electrical fatigue have been analyzed. Unipolar switching time has been modeled as an RC time constant, where C is electric-field dependent. Q'c at a given electric field appears to remain constant over the range of film thicknesses and electrode areas studied. Leakage current density and time-to-breakdown (tBD) for a given electric field degrade with decreasing film thickness. Unipolar stressing causes considerably less fatigue than bipolar stressing, and after 2 × 1011 cycles, a 400nm film still exhibits sufficient Q'c for DRAM operation.
Lead Zirconate Titanate Films Produced by ‘Facing Targets’ RF-Sputtering
Authors: Roy R. A. , Etzold K. F. , Cuomo J. J. 
Published: March 2011

ABSTRACTThe growth of ferroelectric lead zirconate titanate (PZT) films by rf-sputtering using facing targets is described. This study has focused on producing thin (<500 nm) PZT films on a wide range of substrates including magnesium oxide, spinel, alumina, silicon oxide, and the respective substrates coated with platinum. Deposition was from two opposed targets separated by 10–15 cm, with the substrate plane normal to the targets and outside the cylinder defined by the two targets. This geometry was chosen to obtain compositional uniformity and avoid ion bombardment effects. The deposition temperatures ranged from RT to 700 °C and the process gas was a mixture of argon and oxygen. Effects of deposition conditions and post-deposition annealing on film composition, microstructure, and properties were evaluated using Rutherford backscattering spectroscopy (RBS), x-ray diffraction, optical and electron microscopy, and various electrical measurements. Optimization of process conditions is discussed in terms of phase purity, preferred orientation, and minimization of electrode interaction.
Physical and Electro-Optical Properties of Ion Beam Sputtered Thin Film PLZT Ceramic
Authors: Boyer L.L. , Wu A.Y. , Mcneil J.R. 
Published: March 2011

ABSTRACTHigh quality PLZT thin films have been deposited using ion beam sputtering. The deposited material has perovskite crystal structure tetragonal in phase with the c-axis predominantly normal to the surface. Material deposited at temperatures below 450°C has pyrochlore structure while that deposited above 650°C displays polycrystalline characteristics. The deposition rate was approximately 0.2–0.5 Å/sec yielding film thicknesses of ∼4500 Å. The surface morphology of the deposited films is of high quality with a RMS roughness 60% that of magnetron sputtered films.