bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultra-Low Resistance Ni-Based Contacts to n-InP: the Dependence of Contact Resistivity on the Condition of the Metal-Semiconductor Interface
Authors: Fatemi Navid S. , Weizer Victor G.
Published: March 2011

Near-theoretical-minimum values of specific contact resistivity, ρc (in the mid-to-low E-8 Ω-cm2 range) have been achieved for Ni-based contacts to moderately doped (2E18 cm−3) n-type InP. In each case these values are an order of magnitude lower than those previously achieved. These ultra-low resistivities are shown to result when the metallurgical interaction rate between the contact metal and the semiconductor is sufficiently reduced. Several methods of reducing the metal-InP reaction rate and thus achieving lowered resistivity values are demonstrated. We show, for instance, that the introduction of a thin (100Å) Au layer at the metal-InP interface retards metal-semiconductor intermixing during sintering and results in a ten-fold reduction in pc. Another method consists of ensuring the perfection of the near-surface InP lattice prior to and during contact deposition process. Use of this technique has enabled us to fabricate, for the first time, Ni-only contacts with pc values in the low E-8 Ω-cm2 range. We present an explanation for these observations that is based upon the magnitude of the In-to-P atomic ratio at the metal-InP interface.
Shallow Ohmic Contacts to p-InGaAs Based on Pd/Ge with Implanted Zn or Cd
Authors: Ressel P. , Strusny H. , Fritzsche D. , Kräutle H. , Mause K.
Published: March 2011

The development of shallow ohmic contacts for the thin p-InGaAs layer (p≤1*1019 cm−5) of InP-based heterojunction bipolar transistors is a severe challenge to contact technology. While standard metallizations reveal several drawbacks, Pd/Ge-based systems emerged as promising candidates. In this work, Zn or Cd was implanted into the inner Pd contact layer for lowering contact resistivity. We present a study of the electrical and metallurgical properties of Pd/Ge contacts to p-InGaAs, and the influence of Zn and Cd implanted into the metallization. The resistivity of implanted and annealed (450-575 °C) contacts is reduced up to one order of magnitude compared to the unimplanted contact. Backside SIMS measurements show that annealing leads to a very limited interdiffusion at the interface. Cd and Zn diffuse into the InGaAs layer to a depth of approx. 30 and 40 nm, respectively. Due to these features, this implanted Pd/Ge contact scheme is a promising candidate for shallow contacts to p-InGaAs.
Segregant-Assisted Growth of SiGe/Si Heterostructures and their Optical Properties
Authors: Shiraki Y. , Fukatsu S. , Fujita K. , Usami T.
Published: March 2011

A method to realize high quality SiGe/Si heterostructures where surface segregation seriously deteriorates the interface integrity is discussed. After clarifying the mechanism of surface segregation, a new technique, called segre-gant-assisted growth (SAG), where atoms having a strong segregation tendency are introduced at heterointerfaces is proposed and its advantages are demonstrated. Intersubband transition of electrons in the conduction band can be clearly observed even in narrow quantum wells (QWs), and the well width dependence reflecting the square shape potential is obtained in the absorption peak energy. Gas source MBE (GSMBE), which is considered to be quasi-SAG with hydrogen generated at the growth front acting as a segregant, is shown to provide high quality SiGe/Si heterostructures with abrupt interfaces. Highly efficient band edge luminescence is observed in the QWs grown by the SAG method, especially by GSMBE, and the quantum confinement effect is confirmed. Electroluminescent diodes providing band edge luminescence are fabricated by this method, suggesting a high potential for SiGe/Si heterostrucutres in device applications.
Stability of Sulfide Passivated Gallium Arsenide Surfaces
Authors: Solomon J. S. , Petry L. , Smith S. R.
Published: March 2011

The chemical state of (NH4)2S treated (100)GaAs surfaces exposed to ambient conditions for several days was correlated with barrier height measurements. Surface chemistry was characterized by Auger electron spectroscopy and barrier heights were calculated from C-V measurements obtained with a Hg probe. Results show that surfaces are chemically and electrically unstable for several hours following the sulfide treatment. The chemical and electrical states continually changed during ambient exposure up to 300 hours. Although strictly speaking, the surfaces were not passivated, the presence of sulfur did inhibit the formation of Ga and As oxides and the incorporation of carbon. In addition, stable, low barrier heights were observed after ambient exposure for several hours. Barrier heights from C-V measurements using deposited Au and Al contacts were compared to the barrier heights obtained with a Hg probe.
Mechanistic Study of the Deposition of Metals from HF Solutions onto Silicon Wafers
Authors: Parks H.G. , Hiskey J.B. , Yoneshige K.
Published: March 2011

Process chemicals in use today are quite pure, depending on the grade used but can easily be contaminated with metal ions through improper handling or storage techniques. Such metal impurities, if deposited on wafer surfaces during processing can increase reverse-bias junction leakage, degrade oxide breakdown strength and increase metal oxide semiconductor capacitor leakage which in turn can adversely affect the function of ultra large scale integrated (ULSI) circuits. Because of these device effects and since metal contamination can come from several sources it is important to know the deposition level and mechanism on Si wafers from a given process solution. HF based process solution have been investigated due to their historical use in patterning, etching, and their increased use in advanced wafer cleaning processes.

Multi-contaminant experiments have been designed to study the probability of, and mechanism for deposition. It is shown that in general single element deposition is predicted by electrochemical considerations based on redox reactions, however, potential complex synergistic interactions can cause deviations from the simple theory. Specifically, Sn is shown to inhibit the deposition of Ag, and Mo does not deposit in proportion to the amount of Mo in solution, but does deposit on wafers in the presence of Cu and/or Ag. Detailed analysis of Cu and Ag from BOE and Cu from HF shows the deposition: is statistically uniform over bare Si wafers, is independent of substrate doping and rinse time, does not occur on SiO2 is linear with time (up to 25 min) and solution concentration ( up to 500 ppb), shows an Arrhenius behavior with temperature (15 - 55°C) and increases surface micro-roughness. Interpretation of these results with an Evans diagram indicates the deposition is mass transport limited, allowing a first order quantitative theoretical interpretation of the deposition process.
Atomic Scale Control of Si(001) Surface by Wet-Chemical Treatment
Authors: Morita Yukinori , Tokumoto Hiroshi
Published: March 2011

STM observation of the wet-chemical treated Si(001) surface was carried out. On the surface treated by 1%-HF solution (pH=2), the STM images were always rough and hardly exhibited the atomic feature. The STM images on the surface treated by HCl:HF=19:1 solution (pH<1) after 1%-HF dipping were also rough in a macroscopic scale but they occasionally shown atomlike corrugation in a magnified scale. The atomlike corrugation tends to align toward [110] directions which may reflect the ordered structure on Si(001) surface. This result indicates that in the case of etching by the HCl:HF=19:1 solution, the microscopic roughness on Si(001) surface tends to decrease, which might be explained by the steric hindrance effect during extremely slow etching.
Structural and Electrical Characterization of Hydrophobic Direct-Bonded Silicon Interfaces
Authors: Tam Gordon , d'Aragona F. Secco , Theodore N. David
Published: March 2011

Direct wafer bonding is a viable technique for fabricating high-voltage devices. An understanding of the microstructure and electrical behavior of the bonded interface is critical for device fabrication. In this paper, we investigated the microstructure of the silicon-to-silicon bonded interface using cross-sectional transmission electron microscopy and the corresponding electrical behavior using spreading resistance probing. Results indicate that oxide precipitates were present at the bonded interface when Czochralski silicon wafer were used in the process. Oxide precipitates were noticeably absent from the bonded interface when float zone wafers were bonded to each other. We find that oxide precipitates at the interface arise not due to the residual oxide at the surface prior to wafer bonding but due to gettering of oxygen from the Czochralski wafer. Spreading resistance measurements show occurrence of a high resistivity region at the bonding interface whether or not oxide precipitates are present.
Relationship Between Interface Structure and Schottky Barrier Height
Authors: Tung R. T. , Sullivan J. P. , Schrey F.
Published: March 2011

The 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

Interfacial 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

The 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

We 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

The 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

Ellipsometric 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

While 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

The 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

The 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

There 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

Ultrathin 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

The 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

The 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

This 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

The 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

Small 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.
Environmental Effects in Gel Derived Silicates
Authors: Hench L.L.
Published: March 2011

Various methods have been developed for producing crystals, powders, coatings and monoliths from gels [1]. The scientific basis for understanding compositional effects, gelation, aging, drying and densification is also advancing rapidly [2]. However, there is as yet relatively little information on the durability, weathering, or corrosion resistance of glasses, glass-ceramics, ceramics, or composites made via the gel route. Data is also sparse on the effects of vacuum, thermal exposure, or mechanical stress on the stability of gel-derived solids. Relationships between sol-gel processing variables and environmental stability are especially lacking at the present time. Since many end-use applications of gel derived materials involve exposure to severe environments, it is essential that the durability of these materials be established during their development.
Preparation of Thin Composite Coatings by Sol-Gel Techniques
Authors: Martinsen J. , Figat R. A. , Shafer M. W.
Published: March 2011

The formation and characterization of thin ceramic coatings is currently an active area in materials science. Specifically, there has been increased interest in these materials as dielectric and optical layers for advanced microelectronic circuitry [1]. This is in addition to their continued use and evaluation as protective coatings in a variety of applications [2]. One method of forming these coatings is via the sol-gel technique. However, only a few papers have been published in this area [3–7]. Dense silicon dioxide, aluminium oxide and various glass compositions have been deposited in thin film form on various substrates. Further, silicon dioxide films, formed by the sol-gel method, have been nitrided in ammonia at high temperatures and partially converted to an oxynitride [8–11]. These films were shown to be highly non-homogeneous, with a predominance of nitrogen at the surface. Despite the desirability of dense uniform well bonded coatings of the nitrided ceramics, i.e. Si3N4 and the oxynitrides, no method yet exists for the formation of nitrides by the sol-gel method.
The Effect of Hydrolysis Conditions on the Structure and Growth of Silicate Polymers
Authors: Keefer K. D.
Published: March 2011

Small 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

Coagulation 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

High 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

High 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.
Nonaqueous Suspension Properties of Al2O3 and Silicate Glass Powders
Authors: Sacks M.D. , Alam M.I.
Published: March 2011

Colloidal suspensions prepared with nonaqueous liquids are important in ceramic processing operations such as tape casting, slip casting, etc. [1,2]. However, investigations of the properties of such suspensions are limited. In the present work, the suspension behavior of Al2O3 and silicate glass powders was studied using two nonaqueous liquids – methanol (MEOH) and methyl isobutyl ketone (MIBK). Rheological, sedimentation, and electrokinetic properties were determined for various mixed liquid ratios. The effect of polyvinyl butyral resin, a polymeric binder, on silicate glass suspension properties was also investigated.
Microstructural Transformations in Alumina Gels
Authors: Dynys F. W. , Ljungberg M. , Halloran J. W.
Published: March 2011

Microstructural 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

The 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.
Polysilanes as Possible Precursors to Silicon Carbide
Authors: Sinclair R. A. , West Robert
Published: March 2011

The continuing search for new types of high-strength materials, and for performance improvements in existing ceramics, has encouraged several nonconventional approaches to ceramics synthesis. Some of the advantages of polymeric routes have already been demonstrated and include new fabrication procedures leading to continuous fibers, coatings and infiltrated porous structures. At a more fundamental level, polymer pyrolysis can allow control over the microstructure of the final ceramic, with important consequences for both physical and chemical properties (1).
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

Temperature 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

The 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

Single 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

The 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.
Thickness Effect On The Crystallization Kinetics Of Electrolessly-Deposited Ni(P) Thin Films
Authors: Shi L. T. , O'Sullivan E. J. M.
Published: March 2011

In order to understand thickness and interfacial effects on the crystallization kinetics of amorphous solids, Ni(P) thin films electrolessly deposited on Cu seed layers were annealed at constant heating rates or at constant temperatures in a DSC to obtain activation energies andAvrami exponents. It was found that the activation energy of crystallization in Ni(P) changes asa function of sample thickness when the sample thickness is less than 1.0 μm. Furthermore, the Avrami exponent was found to change not only as a function of thickness but also as a function of annealing temperature.
Crystallization Kinetics Of Fe80-yVyB12Si8 Amorphous Ribbons
Authors: Altúzar P. , V́zquez C , BañOS L. , Valenzuela R.
Published: March 2011

The effects of vanadium in the crystallization kinetics amorphous ribbons Fe80-yVyB12Si8 (0.5 < y < 15) has been investigated by Differential Scanning Calorimetry, by using the Avrami, Kolmogorov-Johnson-Mehl-Avrami, and Calka and Radlinski equations. The addition of vanadium to Fe-B-Si alloys leads to an enhancement of stability against crystallization, as shown by an increase in the effective activation energy for crystallization (Eeff = 3.6eV) and an increase in the temperature for the first crystallization peak, as a function of vanadium content (from 780 to 855K). Results also show that the crystallization Mechanism, nucleation rate and dimensionality of growth are constant throughout the crystallization process in the composition range investigated.
DSC and Mössbauer Studies of Fe80B20 Crystallization
Authors: Malizia Federica , Ronconi Franco
Published: March 2011

Differential Scanning Calorimetry has been used to investigate the mechanism of the isothermal crystallization kinetics in Fe80B20 Metallic glass. It is shown that the whole crystallization analysis must include, not only a crystal nucleation-and-growth process, but also a grain-growth process and that these two processes are separated in time during isothermal annealing. These processes have been studied directly finding the parameters which characterize their Mechanism. From the theoretical Johnson-Mehl-Avrami equation describing the nucleation-and-growth process, it was possible to calculate the evolution of the transformed fraction of the material as a function of the annealing time. To infer the meaning of the transformed fraction, samples subjected to different thermal treatments have been studied by Mössbauer Spectroscopy. Our results reveal that the transformed fraction is the sum of the crystalline component formed by all atoms located in the lattice of the grains and the interfacial component composed of atoms in the interfacial regions between grains.
Solid-Phase Epitaxial Crystallisation Of GexSi1−x Alloy Layers
Authors: Elliman Robert G. , Wong Wah-Chung , Kringhøj Per
Published: March 2011

Thermally-induced solid-phase epitaxial crystallisation (SPEC) and ion-beam-induced epitaxial crystallisation (IBffiC) of amorphous GexSi1−x alloy layers is examined for three different starting structures: a) strain-relaxed alloy layers of uniform composition, b) strained alloy layers of uniform composition, and c) Ge implanted Si layers. Thermal annealing experiments show that the activation energy for strain-relaxed alloys is higher than that expected from a simple extrapolation between the activation energies of Si and Ge, and exceeds that of Si for x ≤ 0.3. Experiments on thin strained layers show that MBE grown strained layers which are stable during annealing at 1100°C for 60 s are also fully strained after SPEC, whereas layers which relax during annealing at 1100°C also relax during SPEC. Experiments on ion-implanted GexSi1−x structures show that fully strained Si/GexSi1−x/Si heterostructures can be fabricated for ion fluences below a critical fluence, and as for uniform alloy layers that this critical fluence is accurately predicted by equilibrium theory. Strain relaxation during SPEC of uniform alloys and implanted structures is shown to be correlated with a sudden reduction in crystallisation velocity which is believed to be caused by stress-induced roughening or faceting of the crystalline/amorphous interface. SPEC of thick (800 nm) implanted layers is shown to be limited by competition from ion-beam induced random crystallisation, while thin (120 nm) uniform alloys and implanted structures are shown to crystallise epitaxially and to exhibit similar behaviour to thermally annealed samples under certain conditions.
On the Determination of Partial RDFs for Amorphous Materials
Authors: Qin L. C. , Hobbs L. W.
Published: March 2011

Radial distribution functions (RDFs) for vitreous silica (V-SiO2) have been obtained from energy-filtered electron diffraction data obtained in the HB5 scanning transmission electron Microscope. Results have been compared with those obtained from high-resolution neutron diffraction experiments, and are in good agreement within experimental errors. It was found to be impractical to obtain partial RDFs for this material from combined neutron, X-ray and electron diffraction data, because the similarities in characteristics of X-ray and electron scattering cause indeter-Minacies. A criterion equation has been given to determine feasibility.
Density Reduction: A Mechanism For Amortization at High Ion Doses
Authors: Specht E. D. , Walko D. A. , Zinkle S. J.
Published: March 2011

At cryogenic temperatures, the accumulation of vacancy-interstitial pairs in Al2O3 from atomic displacements associated with ion implantation produces amorphization. At room temperature, these pairs recombine, and amorphization occurs only at high doses. X-ray reflectivity measurements show that amorphization of the surface of Al2O3 implanted at room temperature with 160 keV Cr+ ions is preceded by a progressive reduction in near-surface density. Monte Carlo simulations show that this density reduction can be accounted for by high-energy-transfer collisions which knock atoms deep into the target, leaving widely separated vacancies and interstitials, which do not recombine. Electron Microscopy shows that at least some of these vacancies condense into voids. We propose that this reduction in near-surface density can lead to amorphization at high doses. We present simple approximations for the density reduction expected for different ions and targets.
Dopant Activation And Epitaxial Regrowth in P-Implanted Pseudomorphic Ge0.12Si0.88 Layers on Si (100)
Authors: Lie D. Y. C. , Cams T. K. , Theodore N. D. , Eisen F. , Nicolet M.-A. , Wang K. L.
Published: March 2011

A pseudomorphic Ge0.12Si0.88 film 265 nm thick grown on a Si (100) substrate by molecular beam epitaxy was implanted at room temperature with a dose of 1.5 × 1015 cm2 of 100 keV P ions. The projected range of the ions is about 125 nm, which is well within the film thickness. Only the top portion of the Ge0.12Si0.88 layer was amorphized by the implantation. Both implanted and non-implanted samples were subsequently annealed in vacuum for 30 Minutes from 400 °C to 800 °C. Values of electron Hall sheet mobility and concentration in the implanted Ge0.12Si0.88 epilayer were measured after annealing. The solid phase epitaxial regrowth is complete at 550 °C, where the implanted phosphorus reaches - 100 % activation. The regrown Ge0.12Si0.88 layer exhibits inferior crystalline quality to that of the virgin sample and is relaxed, but the non-implanted portion of the film remains pseudomorphic at 550 °C. When annealed at 800 °C, the strain in the whole epilayer relaxes. The sheet electron mobility values measured at room temperature in the regrown samples (Tann ≥ 550 °C) are about 20% less than those of pure Si.
Nonequilibrium States of Symmetric Tetraalkylammonium Halides
Authors: Xenopoulos A. , Mucha M. , Wunderlich B.
Published: March 2011

The nonequilibrium behavior of symmetrical tetra-n-alkylammonium halides is described from a study of the transition behavior using thermal analysis and hot-stage optical Microscopy. Results are discussed in terms of reversibility, supercooling, sharpness of transitions on thermal cycling, and glass transitions. The transitions of plastic to rigid crystals have the largest supercoolings. Gradual disordering on heating and incomplete ordering on cooling are found for some of the salts and represent interesting examples of order/disorder and glass transitions with reduced cooperativity.
Crystallization From Polymer Blends
Authors: Stein Richard S.
Published: March 2011

Binary polymer blends in which one or both components crystallize have been considered. These May be miscible or immiscible in the amorphous state, and phase separation may occur along with crystallization. The rates of these two processes vary differently with temperature, so the consequent morphology and properties depend upon the temperature history. For Miscible blends, the glass transition temperature depends upon composition. This affects diffusion so that crystallization kinetics varies as composition changes. If only one component crystallizes and the other is rejected, this rejected component diffuses away from the growing crystalline regions in a manner dependent upon the interaction between components.

These phenomena are studied using a variety of techniques such as calorimetry, x-ray diffraction and scattering, and small-angle light and neutron scattering for a number of polymer systems.
Small Angle X-Ray Scattering of Crystalline Polymer Blends
Authors: Huo Peter P. , Cebe Peggy , Capel Malcolm
Published: March 2011

Binary blends of a semicrystalline polymer, poly (butylene terephthalate), PBT, with an amorphous polymer, polyarylate, PAr, were studied for a wide range of compositions. SMall angle x-ray scattering, thermal and mechanical analyses were conducted to determine the location of the uncrystallizable PAr relative to the crystal lamellae of PBT, for blends crystallized by heating from the quenched state. Comparison of experimental and calculated long periods indicates that interlamellar PAr placement becomes less probable as the PAr composition increases. When PBT crystallizes in these blends, Most PAr is rejected from the regions near the crystal surfaces when PAr fraction exceeds about 0.40.
Silicon Crystallization from Annealed Cu/A-Si:H Bilayers: A Multitechnique Study
Authors: Achete C. A. , Bernardino L. , Freire F. L. , Mariotto G. , Niehus H.
Published: March 2011

Silicon crystallization has been observed to occur in copper/a-Si:H thin film bilayers annealed at 280 °C. Copper-silicide formation was observed after annealing at 200 °C. Samples characterization was made by a combination of several analytical techniques: scanning electron Microscopy, Raman spectroscopy through a microscope probe, Auger electron spectroscopy, elastic recoil detection analysis and Rutherford backscattering spectrometry. The possible role of hydrogen in this process is discussed.
Effect of Pb Content on the Transformation of Sputtered PbxZr0.4Ti0.6O3 Thin Film
Authors: Joo Jae-Hyun , Kill Deok-Sin , Joo Seung-Ki
Published: March 2011

PZT (PbxZr0.4Ti0.6O3) thin films were prepared by reactive co-sputtering and annealed by RTA (Rapid Thermal Annealing). Transformation kinetics and effect of Pb content on the transformation were intensively studied using EMA (Effective Medium Approximation). It has been found that depending on Pb content as well as RTA temperature, the crystal structure of PZT films changed greatly. It turned out that the transformation temperature for the perovskite phase can be lowered and the width of transition temperature region was reduced by increasing Pb content in the films. Dependence of transformation path on the Pb content has been studied.