bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationship Between Interface Structure and Schottky Barrier Height
Authors: Tung R. T. , Sullivan J. P. , Schrey F. 
Published: March 2011

ABSTRACTThe clear dependence of the Schottky barrier height (SBH) on the structure of a metalsemiconductor (MS) interface is described for a few high-quality epitaxial MS systems. Polycrystalline MS interfaces, for which such a dependence is often absent, are shown to display clear evidence for SBH inhomogeneity, in direct conflict with the Fermi level (FL) pinning concept they helped to create. Recent theoretical calculations show that many basic tenets of the interface state pinning models are unfounded. The redistribution of charge as a result of bonding at the MS interface seems to be the most important contribution to the interface dipole and, hence, the SBH.
Interfacial Cohesion Control by Solute Segregation
Authors: Wang Jian-Sheng 
Published: March 2011

ABSTRACTInterfacial cohesion is determined by the cohesive energy of the interface. Knowing the segregation energies of solute in the interface and on the adjoining free surfaces and mobilities of segregant atoms, the change in cohesive energy of the interface due to solute segregation can be evaluated within the framework of the Langmuir-McLean isotherm. A control of the interfacial cohesion is thus achievable by promoting segregation of the desired solute.
Interfacial Compatibility of Ti3Al with Various Ceramic Reinforcements
Authors: Si Weimin , Li Pengxing , Wu Renjie 
Published: March 2011

ABSTRACTThe interfacial compatibility of SiC, Al2O3, and TiC with Ti3Al alloy has been evaluated. Thin films of these three ceramics materials were deposited on Ti3A1 substrates. The thin film diffusion couples were annealed from 600°C to 1000°C, and the thickness of the interfacial layer was obtained from Auger Electron Spectroscopy (AES) concentration depth profiling. The reaction products were identified by X-ray Diffraction (XRD) and AES. In the A12O3/Ti3A1, obvious interdiffusion occurred with some reaction products. In the SiC/Ti3Al, significant interdiffusion and reactions occurred in the interfacial layer, and multilayer reaction zones were found. In the TiC/Ti3Al, the reaction product was primarily the P(Ti3AlC) phase. Kinetic studies of the growth of the interfacial layer showed that SiC reacted most severely with Ti3Al, TiC less so, and AI2O3 the least. The compatibility of these three systems has been assessed.
A New Method for the Simultaneous Analysis of I-V/T and C-V/T Measurements of an Au/P-Inp Epitaxial Schottky Diode
Authors: Cova P. , Singh A. , Masut R. A. , Currie J. F. 
Published: March 2011

ABSTRACTWe have developed a new approach to analyze the current- voltage (I-V) characteristics of a tunnel metal-interface layer - semiconductor (MIS) diode which takes into account the voltage dependence of interface states distribution (Nss) and the barrier lowering due to image force. Our method of analysis uses simultaneously the I-V/T and C-V/T data to determine the characteristic parameters of an MIS diodes and is ideal for new epitaxial materials and devices where the carrier density is not known precisely before hand. The experimental verification of our approach to analyze the nonideal I-V/T and C-V/T characteristics of MIS diodes was done by comparing the values of Nss extracted from the room temperature forward I-V characteristics of a p-InP/Au MIS diodes with those obtained by the multi-frequency admittance method. Excellent agreement between the values of Nss determined by two different techniques strongly support the validity of our theoretical expression for the I-V/T characteristics and the method of analysis. Our results indicate that the interface layer thermionic emission was clearly the dominant mechanism of the forward current transport in epitaxial Au/p-InP MIS diodes over the temperature range 200–393 K. The transmission coefficient of the interface-layer obtained from the reverse I-V characteristics has a value of 1.43×10−3 (±7%).
Computer Simulation of Free-Surfaces in Close-Packed Structures
Authors: Fernández J.R. , Monti A.M. , Pasianot R.C. 
Published: March 2011

ABSTRACTThe static relaxation method was applied to the study of free-surfaces in fcc (Ni,Al,Ni3Al) and hcp (Ti,Zr,Mg) lattices bounded by many-body interaction potentials of the EAM-type. The present calculated changes in interlayer spacings were compared with measured and other theoretical results. Vibrational modes of atoms in the surface and in planes below the surface were analyzed in the Einstein and the "cluster" approximations. The latter explicitly includes coupling effects. Frequency variations with the distance to the surface are obtained in the former approximation and vibration modes for a set of atoms in the second one.
Ellipsometric Study of the Interface Between Silicon and Silica
Authors: Doremus R. H. , Kao S. C. 
Published: March 2011

ABSTRACTEllipsometric measurements of surfaces of oxidized silicon give information on the optical properties, structure and composition of the interface between the silicon and oxide. From such measurements in ambient liquids with different refractive indices, some close to that of the oxide, we conclude that there is an interfacial layer about one nm thick at all oxide thicknesses. This layer is either a transition layer of partially oxidized silicon or a layer of silicon of higher absorption than bulk silicon. The oxide has the refractive index of vitreous silica at all thicknesses.
Sulfonated Metal-Oxide Surfaces: What Makes them So Acidic?
Authors: Ferris Kim F. 
Published: March 2011

ABSTRACTWhile some metal-oxide surfaces can be classified as acidic, after reacting with H2SO4 their acidity can be even higher than the parent sulfuric acid. In this paper, ab initio electronic structure calculations (3-21G+*//3-21G*) were performed on a series of model surfaces to examine these sulfonated species as strong, possibly even superacids. Our results indicate that the polarizing nature of the metal-oxide / sulfonate interaction stabilizes strong Bronsted and Lewis acid sites at the M-O surface and the sulfur center. Thermodynamic analysis has been performed to provide information for experimental verification.
Interfacial Reactions of Ti-24Al-11Nb Alloy with Al2O3
Authors: Si Weimin , Li Pengxing , Wu Renjie 
Published: March 2011

ABSTRACTThe interfacial reactions and interdiffusion between Al2O3 and Ti-24Al-11Nb (at%) alloy have been investigated. Diffusion couples were fabricated by thermal sprayed Al2O3 film onto Ti-24Al-11Nb substrate, and then annealed at 1200°C. Interfacial layers were characterized using electron probe microanalysis (EPMA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The layered structure of interface region was observed which showed the diffusion controlled characteristics. In the reaction zones, the reaction products consisted mainly of TiO, TiO2, and Al2TiO5. Adjacent to the reaction zones, there existed β phase free zone and β phase lacking zone. The β phase free zone resulted from Nb depletion of this region. The reaction mechanism has been discussed using thermodynamic approach.
Growth Mode of CeO2 on Si Surface
Authors: Chikyow Toyohiro , Tye Lee , El-Masry Nadia A. , Bedair Salah M. 
Published: March 2011

ABSTRACTThe interface structure and electrical properties of CeO2/Si (111) grown by laser ablation in ultra high vacuum was investigated by high resolution transmission electron microscopy .Auger electron spectroscopy and capacitance-voltage measurement. The deposited film was single crystalline CeO2 as indicated by RHEED and x-ray diffraction observations. However, during the deposition, a reaction between CeO2 and Si occurred at the interface. This reaction resulted in the formation of an oxygen deficient amorphous CeOX layer and a S1O2 layer. Post annealing in oxygen atmosphere caused the disappearance of the amorphous CeOX and the regrowth of crystalline CeO2. The SiO2 thickness was also increased by annealing. The modified structure of CeO2/SiO2/Si showed a higher break down valtage, compared with the as-deposited sample. From these results, a combination of CeO2 and SiO2 can have a great potential for SOI structure.
Electrodeposited Cobalt-Tungsten as a High-Temperature Diffusion Barrier for Graphite-Fiber/Nickel Composites
Authors: Wheeler N. S. , Lashmore D. S. 
Published: March 2011

ABSTRACTThere is a growing demand for advanced composites which can maintain their structural strength in high-temperature environments, particularly for aerospace applications. The use of graphite fiber/nickel metal matrix composites would be desirable if the deterioration of mechanical properties resulting from interdiffusion of carbon and nickel at temperatures in excess of 600°C could be avoided. The present research concerns an electrodeposited cobalt alloy coating containing 5-10.5 at-% tungsten, which was designed to serve as a diffusion barrier between graphite fibers and a nickel matrix. The resulting graphite/Co-W/Ni composite was tested under various time/temperature conditions, and the coating was shown to inhibit diffusion for up to 24 hr at 800°C. Annealed and unannealed coated fibers were analyzed by x-ray diffraction and by transmission electron microscopy The as-deposited coating was found to contain both h.c.p. and f.c.c. cobalt, whereas only f.c.c. was observed after annealing at 1100°C for 1.5 hours. WC was found at the coating/fiber interface.
Degradation in Oxide Reliability Due to the Presence of Nitrogen in the Oxidation Ambient
Authors: Hames Greg A. , Wortman J. J. , Beck S. E. , Shemanski B. J. 
Published: March 2011

ABSTRACTUltrathin rapid thermal oxides have been formed in oxygen with varying levels of nitrogen incorporated into the oxidation ambient. Metal-oxide-semiconductor capacitors and MOSFET devices were subsequently fabricated and tested. Device reliability was degraded by the addition of nitrogen into the oxidation ambient. Time-independent catastrophic breakdown measurements showed a large increase in the number of extrinsic breakdowns in devices formed in higher levels of nitrogen. Device performance was measured by interface trap density, subthreshold slope, channel mobility and threshold voltage. A small increase in the interface trap density was observed for increasing levels of nitrogen in the oxidation ambient. However, no trends were observed for MOSFET devices in terms of subthreshold slope, channel mobility or current drive. No improvement in the interface state generation rate due to nitrogen incorporation in the oxidation ambient was observed in this study. X-ray photoelectron spectroscopy detected no nitrogen in the oxides indicating less than 1% nitrogen incorporation.
On the Mechanism of Ultra Thin Silicon Oxide Film Growth During Thermal Oxidation
Authors: Gusev E.P. , Lu H.C. , Gustafsson T. , Garfunkel E. 
Published: March 2011

ABSTRACTThe growth of ultra-thin oxide films by the thermal oxidation of silicon has been studied by low and medium energy ion scattering spectroscopies (LEIS and MEIS) and X-ray photoelectron spectroscopy (XPS). To help elucidate the diffusional and mechanistic aspects of oxide growth we have used sequential isotope oxidation (18O2 followed by 16O2). LEIS demonstrates that both 18O and 16O atoms are on the silicon surface under our growth conditions. MEIS also distinguishes 18O from 16O and gives a depth distribution for both with high accuracy. Our results show that several key aspects of the Deal-Grove model (oxygen diffusion to the Si-SiO2 interface and oxide formation at the interface) are consistent with our results for 50Å films. For very thin oxide films (15Å or less), we found a mixed isotopic distribution in the film, demonstrating more complex oxidation behavior.
Laser-Stimulated Changing of Micromechanical Properties in the Monocrystalline and Porous Silicon
Authors: Makara Volodimir A. , Vesna Galina V. , Rudenko Olga V. , Sizontov Viktor M. 
Published: March 2011

ABSTRACTThe optical and mechanical properties of silicon surface subjected to thermal, chemical, electromechanical and laser treatment have been studied. A special electroluminescence spectrum of silicon monocrystal with porous layer obtained by means of selective etching has been given. It was shown that radiating of monocrystal and porous silicon by laser irradiation with the energy of (1÷5)• 105j/m2 (λ=1,06 μm) allowed to change their microplasticity and microhardness by 20 -50%.
Control of Si-SiO2 Interface Properties in MOS Devices Prepared by Plasma-Assisted and Rapid Thermal Processes
Authors: Lucovsky G. , Yasuda T. , Ma Y. , Hattangady S.V. , Xu X-L , Misra V. , Hornung B. , Wortman J.J. 
Published: March 2011

ABSTRACTThis paper describes the preparation of silicon-based metal oxide semiconductor, MOS, devices, capacitors and field effect transistors, FETs, using deposited oxide dielectrics. A critical aspect of the device fabrication process is the way the Si-SiO2 interface is formed; e.g., either before, during, or after the oxide deposition. We have studied different methods of fabricating Si-SiO2 heterostructures, and have concluded that the implementation of independently controllable and sequential process steps for (i) interface formation, and (ii) oxide deposition consistently yields MOS devices with electrical properties that are superior to those of devices fabricated under other processing conditions which include specifically interface formation during the oxide deposition.
Mechanism of O2 Molecule Adsorption and Subsequent Oxidation of Dimers on Si(001) Surfaces
Authors: Hoshino T. , Tsuda M. , Oikawa S. , Ohdomari I. 
Published: March 2011

ABSTRACTThe adsorption reaction of O2 molecule with symmetric dimers on the Si(001)–2×1 reconstructed surface has been investigated by ab initio molecular orbital calculations. Detailed analysis of the lowest energy reaction path has revealed that there exists a metastable state in which O2 molecule adsorbs on silicon dimer without dissociation, the dissociation of O2 molecule requires large activation energy, and a silicon oxide and an isolated oxygen atom are produced after the reaction has been completed. The activation energy required for the conversion from the metastable state to the final products has been estimated to be 60.4 kcal/mol. This result suggests that a symmetric dimer on the Si(001)–2×1 surface is hardly oxidized at room temperature. This conclusion is consistent with the recent STM observations that the initial stage of oxidation starts from the dimer defect sites on the Si(001) surface. On the contrary, it has been found that no activation energy is required for the oxidation reaction by O atom.
Structure of Soluble Silicates
Authors: Schaefer Dale W. , Keefer Keith D. 
Published: March 2011

ABSTRACTSmall angle x-ray scattering (SAXS) is the technique of choice for the determination of structure on the 10–1000Å scale. We have used this technique to study the growth and topology of the macromolecules which precede gelation in several chemical systems used in sol-gel glass technology. The results show that branched polymers, as opposed to colloids, are formed. The alcoholic silica system is akin to organic systems where gelation occurs through growth and crosslinking of chain molecules. Data are reported from both the Porod and Guinier regions of the SAXS curve and these data are interpreted in terms of geometrical structures predicted by various disorderly growth processes. The results indicate that the degree of crosslinking can be controlled by catalytic conditions. The degree of crosslinking may, in turn, control phase separation and processability to a dense glass.
The Effect of Hydrolysis Conditions on the Structure and Growth of Silicate Polymers
Authors: Keefer K. D. 
Published: March 2011

ABSTRACTSmall angle scattering experiments have demonstrated that the structure of the silicate species produced by the hydrolysis of silicon alkoxides in non-aqueous solvents ranges from extended, weakly cross-linked polymers to highly condensed, colloidal particles. In contrast, inorganic, aqueous silicate solutions yield primarily colloidal particles because the silicate species have a number of different silanol sites available and the preferred condensation reaction is that of weakly condensed species with highly cross-linked branch sites, such as those on an amorphous silica surface. It is proposed that in the alkoxide systems, however, the hydrolysis reaction may control the number and type of silanol sites available for condensation. In acid catalyzed reactions, the rate of hydrolysis of a silicate tetrahedron tends to decrease as alkoxide groups are removed. This favors the production of silanol sites on the end of chains, thus generating linear polymers. In base catalyzed reactions, it is argued that each subsequent hydrolysis of a tetrahedron should proceed more rapidly than the previous one, producing numerous branch points which are the preferred sites for condensation.
Rheological Properties of an Alkoxide Derived Hlw Slurry Feed
Authors: Cadoff L. H. , Smith-Magowan D. , Harrison D. E. , Pope J. M. 
Published: March 2011

ABSTRACTCoagulation of HLW feed slurry can result from the interaction between acid metal cations and soluble silicates/silica. Feed slurry viscosity depend on a number of factors: (a) concentration and composition of the waste slurry electrolytes, (b) type and concentration of silica and silicate constituents in the glass former, (c) pH of the slurry feed, and (d) degree and order of mixing of the glass former with the waste sludge. Coagulation can be avoided by mixing to achieve a good dispersal of glass former globules in the waste slurry even when pH and electrolyte content favor it.
Preparation of Strontium Titanate Ceramics and Internal Boundary Layer Capacitors by the Pechini Method
Authors: Budd K. D. , Payne D. A. 
Published: March 2011

ABSTRACTHigh purity, fine-grain size, SrTiO3ceramics were fabricated from powders which were chemically derived by the Pechini method. The preparation is based upon a thermally polymerizable water-ethylene glycol-citric acid system in which a wide range of metal alkoxides, carbonates, and metal salts are soluble. The process is a closed system, and lends itself to the preparation of complex oxides which can contain numerous additives and dopants. In this study, Wdoped SrTiO3powders were prepared with various Sr:Ti ratios, and fine grain internal boundary layer capacitors were fabricated by controlled segregation in sintering. Characteristics of the resin, powder, microstructures, and electrical properties are reported. The advantages and disadvantages of this method of chemical preparation for ceramic materials are noted.
lH Nmr Studies of the Sol-Gel Transition
Authors: Assink Roger A. , Kay Bruce D. 
Published: March 2011

ABSTRACTHigh resolution 1H NMR spectroscopy has been employed to study the dynamics of the sol-gel transition in simple silicates. High magnetic fields (360 MHz) were used to detect and identify the various chemical species present in the Si(OCH2CH3)4:C2H5OH:H2O sol-gel system. Using these techniques, the time evolution of the reactant and product species were monitored. The results of these studies have shown that acid and base catalyzed systems react along very different chemical pathways and that the elementary hydrolysis and condensation reactions occur on widely different time scales.
Microstructural Transformations in Alumina Gels
Authors: Dynys F. W. , Ljungberg M. , Halloran J. W. 
Published: March 2011

ABSTRACTMicrostructural development in alumina gels is dominated by a series of phase transformations between the hydrous oxides to transition alumina phases, between transition phases, and transformation to alpha-alumina. These microstructural transformations are illustrated in boehmite AlOOH and bayerite Al(OH)3 gels.
Processing of Advanced Ceramic Composites
Authors: Rice Roy W. 
Published: March 2011

ABSTRACTThe field of ceramic composites is reviewed as an outstanding example of where more sophisticated chemistry can aid ceramic processing. Processes reviewed, mostly from work of the author and colleagues, include use of solution, polymer and high temperature chemistry, e.g. in sol-gel, polymer pyrolysis, solid state, and chemical vapor deposition processes. Future needs and opportunities for chemistry in ceramic processing are also discussed, e.g. coating part or all the matrix or its precursor onto the particulates or fibers of the resultant composite.
Thermal Stability and Relaxation Processes of The Ti-Cu- and Ti-Ni-Based Metallic Glasses
Authors: Babich Nikolay G. , Dashevsky Nikolay N. , Nakonechna Olesja I. , Revo Sergey L. , Zakharenko Nikolay I. 
Published: March 2011

ABSTRACTTemperature dependences of magnetic susceptibility for Ti-Cu- and Ti-Ni-based amorphous alloys have been obtained in the temperature range 300–850 K. All investigated alloys are shown to be Pauli paramagnets. Fe and Co impurity atoms possess zero localized moment due to effect of spin moment quenching. Relaxation processes were studied using thermopower measurements. It was shown the thermal stability of investigated alloys is determined predominantly by Nagel-Tauc electronic criterion.
Ionic Motion and Structure of Ion Conductive Glasses
Authors: Akai T. , Yamashita M. , Yamanaka H. , Wakabayashi H. 
Published: March 2011

ABSTRACTThe dynamic structure of xLi2S-Ga2S3-6GeS2 (x=4 and 6) glasses has been investigated by 7Li nuclear magnetic resonance. In two samples similar values of spin-lattice relaxation time (T1) were obtained. The relaxation mechanism at 20MHz and 78MHz is therefore attributed to the local motion of lithium ions. In the glass corresponding to x=6, which shows higher conductivity, the slow motion of ions showing an activation energy of 24.3kJ/Mol has been detected by the spin-lattice relaxation time in the rotating frame (T1p). This value is comparable to the activation energy determined by the conductivity. The existence of this mode is supported by the motional narrowing of the line width which is sensitive to the motion less than 10kHz.
Characterization of metamict and Glassy Lead Phosphates
Authors: Sreeram A. N. , Hobbs L. W. 
Published: March 2011

ABSTRACTSingle crystals of Pb2P2O7 (beam stable under 200 kV TEM electrons to a fluence > 1027 e/M2 and an ionizing dose > 1014 Gy) were rendered Metamict (amorphized) with ion-implantation (100 kV P+ ions with several fluences between 5 × 1017/M2 - 2 × 1020/M2). Pb2P2O7 and PbO-P2O5 glasses were also ion implanted at identical fluences. Radial distribution functions for metamict and glassy phosphates generated using energy filtered electron diffraction (EFED) data collected on 100 kV field emission STEM (VG HB-5) indicate significant alterations in the medium range order.
Kinetic Study Of Crystallisation In Amorphous Thin Lpcvd Si Films
Authors: Pieraggi B. , Guillemet J. P. , de Mauduit B. 
Published: March 2011

ABSTRACTThe crystallisation behaviour of LPCVD silicon films has been investigated by TEM from in situ isothermal annealing of undoped a-Si films deposited from disilane (Si2H6) at temperatures 450,465 and 480 °C and at gas pressure of 200 MTorr. Nucleation kinetics, grain growth rates and crystallisation kinetics were determined for temperatures ranging from 600 to 675 °C. Nucleation kinetics have been experimentally determined in the early first stages of annealing : they do not show any steady-state rate and are fitted according to a power law. Experimental data for crystallisation kinetics are fitted by an Avrami law without introducing any incubation time.