bluuebunny/crossref_metadata_2025 huggingface dataset:
Superplasticity in P/M Aluminium Alloys
Authors: Higashi K. , Tanimura S. , Ito T.
Published: March 2011

Recent advances in the technologies of powder metallurgy lead to the development of some superplastic aluminium alloys containing a deliberate addition of a large amount of Zr and /or Cr and Mn that exhibit the high strain rates superplasticity. For a few alloy systems, the large elongation more than 500% has been observed over the strain rates of 1×10−1s−1, which rates are two or three orders of magnitude faster than those at which superplasticity is found in conventional superplastic aluminium alloys produced by ingot metallurgy. The high strain-rates superplasticity obtained in both type of fully static recrystallized and dynamic recrystallized P/M aluminium alloys. The decreasing of initial size of grains and/or sub-grains leads to the increasing the strain-rates for superplastic flow in both types of alloys. The refinement of grains or sub-grains size is one of necessary and important to obtain the high strain-rates superplasticity.
An Experimental Study of Cavity Nucleation During Superplastic Deformation
Authors: Xinggang Jiang , Jianzhong Cui , Longxiang Ma
Published: March 2011

Cavity nucleation during superplastic deformation of a high strength aluminium alloy has been studied using a high voltage electron microscope and an optical microscope. The results show that cavities nucleation is due only to superplastic deformation and not to pre-existing microvoids which may be introduced during thermomechanical processing. The main reason for cavity nucleation is the high stress concentration at discontinuties in the plane of the grain boundary due to grain boundary sliding.
Fibre Quality Factors in Papermaking — II The Importance of Fibre Coarseness
Authors: Seth R.S.
Published: March 2011

The effects of fibre coarseness on the papermaking properties of softwood pulps have been demonstrated. While reducing fibre length or strength reduces mainly sheet strength, changes in fibre coarseness influence virtually all pulp properties — drainage, wet-web strength, and the structural, strength, and optical properties of the dry sheets. The effects are large, and are explained on the basis that coarser fibres have thicker walls, are fewer per unit pulp mass, and have smaller specific surface area. Implications for the quality of market chemical pulps are discussed.
Dependence of Fiber/Fiber Bonding on Some Papermaking Variables
Authors: Stratton Robert A. , Colson Norman L.
Published: March 2011

The bond breaking load and bonded area of individual fiber/fiber bonds were measured using a new fiber load elongation recorder (FLER2) and Page's polarized light scattering technique, respectively. Lightly (570 mL CSF) and moderately (345 mL CSF) refined fibers with fines subsequently removed produced bonds of equal strength. Bonds between latewood fibers were substantially stronger than those between earlywood fibers. Polymeric strength aids interacting with the fibers by either covalent or ionic bonding increased the bond strength by a factor of two.
Model Study of Paper Elasticity and Drying Restraints
Authors: Niskanen Kaarlo J.
Published: March 2011

Experiments on laboratory paper sheets have indicated that under certain conditions the elastic modulus is inversely proportional to both the drying shrinkage and dimensional stability. Thus it appears that the elastic response of paper to mechanically and hygroscopically induced stresses is determined by the drying strain or shrinkage of the sheet. It is not clear, however, what effect the geometry of paper network and the properties of papermaking fibers have on the relationship between paper elasticity and drying restraints.

We have developed a model for the study of the elastic properties of paper as a function of the drying shrinkage. The model is based on the assumption that there exists a unique relationship between the elastic properties and dried-in compression of fiber. As a consequence, the elastic properties of a fiber depend on its orientation relative to the principal axes of the paper sheet.

The qualitative features obtained from the model calculations are consistent with experimental observations and independent of details of the elastic properties of fiber. It is clearly shown that no unique relationship exists between the drying strain and elastic modulus of the paper sheet. However, to a reasonable accuracy certain simple relatioships do exist that appear to be of general validity.
Paper Making Furnish as a Composite Blend. Some Wet End Interactions among Furnish Ingredients
Authors: Marton Joseph
Published: March 2011

C.A. Hogart defined paper as “a random bonded fibrous network carrying filler material“. A few thoughts related to this definition and pertaining to paper composites are presented.

A typical papermaking furnish consists of a blend of cellulosic fibers and fines, inorganic fillers and additives. Composition varies according to end use requirements. The fiber network secures desired mechanical and strength properties, fillers contribute to esthetics and good optics. Filler retention is improved by using retention aids. Strength-loss due to filler, use is compensated for, by applying strength additives.

Additives applied at the wet end interact with furnish components. The surface charge, accessible surface area and composition play a role in the interactions. Some typical interactions, involving cationic starch and polyacrylamide, are discussed.
A Mechanism for the Formation of Paper from a Heterogeneous Fiber-Water Mix
Authors: Gess J. M.
Published: March 2011

Studies are presented showing that formation of a sheet of paper from a heterogeneous mix of cellulose fibers and water at the forming section of a paper machine is a three-part process.

The studies were carried out using the Weyerhaeuser-developed G/W Drainage/Retention System of following the forming portion of the papermaking process and is a summary of work carried out over a five-year period of time.
Polyaluminum Hydroxychloride Application in Neutral pH Rosin Sizing of Paper
Authors: Wortley Barbara H. , Steelhammer Joe C.
Published: March 2011

Commonly referred to as PAC, a series of polyhydroxide chlorides of aluminum with the general formula Aln(OH)mCl3n−m are being increasingly used as rosin size bonding agents, drainage aids and retention aids in papermaking.

The manufacturing route chosen, the process kinetics and degree of neutralization affect the product produced and its reactions in the paper-making system. Production methods and procedures for quantifying the products produced are described.

Dispersed rosin size and PAC can be applied to a papermaking system operating at pH 6 to 7.3.

Sizing specifications are met and paper with non-slip characteristics, good machine glaze surface and printability is produced.
Fabrication of Composite Materials from Fibrous Precursors Using Paper Making Procedures
Authors: Zabasajja J. N. , Ahn Soonho , Wu Tony , Krishnagopalan A. , Tatarchuk B. J.
Published: March 2011

Novel composite materials have been fabricated from fibrous precursors using paper making procedures. Small metal fibers (2 μm in diameter) and carbon fiber bundles (20 μm in diameter) were combined with cellulose (as the binding agent) into an interwoven paper preform. The composite paper preform was then sintered at high temperatures in a controlled atmosphere, subsequently removing the cellulose and forming a sinter-bonded composite structure. The sinter bonding of the metal locked the metal fibers and provided high mechanical flexibility and structural integrity to the resulting composite structure. The composite structures were characterized using scanning electron microscopy, electrochemical and kinetic measurements. The optimization of these structures for high energy density applications was demonstrated through these measurements.
Novel Cationic Pigmentary Materials and their Use
Authors: Lauzon R.V.
Published: March 2011

Previous work has shown that certain cationic solutes can adsorb “specifically” at the solid-solution interface [1,2]. To do this, a counterion must have a high enough “specific adsorption potential”. This is difficult to predict theoretically, and can best be studied is by electrokinetic titration.

In this work, we have performed electrokinetic titrations of a diverse group of pigmentary materials such as clays, TiO2 and silicates. Using this information, we have cationized TiO2 and measured the effect on its retention in paper. A Dynamic Handsheet Mold was used for this work. Kaolin clay was also cationized and used to prepare cationic paper coatings.
Composite Systems of Lignocellulosics with Synthetic Polymers
Authors: Narayan Ramani , Neu Robert P.
Published: March 2011

Incompatible polymer blends are known to have inadequate mechanical properties due to poor adhesion and high interfacial tension between the phases. One such blend that displays this type of behavior is the cellulose acetate-polystyrene blend and is typical of lignocellulosic-synthetic polymer blend systems. Tailor-made cellulose acetate-polystyrene graft copolymers have been synthesized and used as compatibilizers (emulsifiers) to reduce the interfacial tension and improve interfacial mixing. Thermal analyses and morphological studies of the blends with and without the graft copolymer demonstrated that this was indeed the case.
Atomically Abrupt and Smooth Heterointerfaces: An Optical Investigation
Authors: Warwick Colin A. , Jan William Y. , Ourmazd Abbas , Harris Timothy D. , Christen JÜdrgen
Published: March 2011

Luminescence spectra from quantum wells are routinely interpreted in terms of atomically smooth and atomically abrupt interfaces. Here we show that this interpretation is inconsistent with photoluminescence, photoluminescence excitation, and quantitative microscopic (chemical lattice imaging) results. We argue that the discussion of interfacial roughness in terms of “an island size” is too naive. A full characterization of an interface requires the description of a “roughness spectrum”, specifying the amplitude of the interfacial corrugation vs corrugation wavelength over the relevant length scale.
Wedge Tem Characterization of Movpe GaInAs/InP Layers, Concentration Grading at Interfaces
Authors: Spycher R. , Stadelmann P.A. , Buffat P.A.
Published: March 2011

Wedge Transmission Electron Microscopy has many advantages, one of which is the concentration determination in III-V semiconductors with a fairly good accuracy. This allows us to determine the concentration variation during the growth of GaInAs/InP multilayered structures and to deduce the concentration grading at the interface GaInAs/InP (As in InP) and the abruptness of the InP/GaInAs interface.
Atomic Layer Epitaxy
Authors: Usui Akira
Published: March 2011

Atomic layer epitaxy(ALE) of III-V compound semiconductors is reviewed. This technology has grown in recent years because of potential applications to nanometer-order structures as well as to monolayer/cycle growth with high-uniformity in growth thickness, and to excellent selective-area growth. Recent developments in chloride ALE of various compounds and heterostructures are described. Potentials of ALE for producing such fine structures are shown.
Interface Formation and the Heteroepitaxy of ZnSe on Si.
Authors: Bringans R. D. , Biegelsen D. K. , Ponce F. A. , Swartz L.-E. , Tramontana J. C.
Published: March 2011

Zinc selenide films have been grown heteroepitaxially on Si(100) substrates by molecular beam epitaxy. The growth has been carried out for raised substrate temperatures and also at room temperature followed by solid-phase epitaxial (SPE) regrowth. The ZnSe films have been characterized by a number of surface-sensitive techniques and both the interface and the bulk material have been examined with high resolution transmission electron microscopy (HRTEM). We find that an interlayer, which is most likely SiSex, is present between the ZnSe film and the Si substrate for growths made at 300 °C and causes loss of epitaxy. In the case of room temperature deposition and SPE, it is absent, leading to good epitaxy. In the latter situation, the films are very uniform and there is a 4° rotation of the ZnSe crystal axes relative to those of the Si substrate.
Undoped GaAs with a Low Electron Concentration Grown on Si by Mocvd
Authors: Nozaki Shinji , Wu A. T. , Murray J. J. , George T. , Umeno M.
Published: March 2011

We have successfully grown undoped GaAs of very high resistivity on Si by MOCVD. The back and side edges of the Si substrate were coated with a Si3N4/SiO2 stacked layer to suppress Si incorporation Into GaAs by the gas phase transport mechanism during MOCVD growth. A 3- μm-thick GaAs layer was grown on this Si substrate at 750 °C in an atmospheric MOCVD reactor using the two-step growth technique. The electron concentration measured by a Polaron C-V profiler is 3xl0l4 cm−3, as low as that of GaAs grown on GaAs substrate, up to the depth of 1.5 μm from the surface.
Selective Epitaxy of Compound Semiconductors in Movpe Growth: Growth, Modelling, and Applications
Authors: Kuech T.F. , Goorsky M. , Palevsky A. , Solomon P. , Tischler M.A.
Published: March 2011

Selective cpitaxial growth during metal-organic vapor phase epitaxy (MOVPE) can be accomplished over a wide range of growth conditions through the usC of alternative growth precursors. We have used chlorine-containing growth precursors, such as diethyl gallium chloride, (C2H5)2GaCl, to selectively grow GaAs and AlxGa1x As. The growth process has been thermodynamically modelled in order to estimate relative growth rates and alloy composition. This model indicates that near the growth front the growth process is chemically similar to the inorganic-based growth of compound semiconductors. This growth technique has been applied to the growth of extremely low resistance ohmic contact structures and quantum well structures.
Growth and Characterization of InP/GaAs on Soi by Mocvd
Authors: Karam N.H. , Haven V. , Vernon S.M. , Namavar F. , El-Masry N. , Haegel N. , Al-Jassim M.M.
Published: March 2011

Epitaxial InP films have been successfully deposited on GaAs coated silicon wafers with a buried oxide for the first time by MOCVD. The SOI wafers were prepared using the Separation by IMplantation of Oxygen (SIMOX) process. The quality of InP on SIMOX is comparable to the best of InP on Si deposited in the same reactor. Preliminary results on defect reduction techniques such as Thermal Cycle Growth (TCG) show an order of magnitude increase in the photoluminescence intensity and a factor of five reduction in the defect density. TCG has been found more effective than Thermal Cycle Annealing (TCA) in improving the crystalline perfection and optical properties of the deposited films.
Mbe Growth of High Quality (111)B GaAs, GaInAs, and AlInAs
Authors: Harshman P. , Malloy K.J. , Walker J. , Smith J.S. , Wang S.
Published: March 2011

Growth of (111)B oriented GaAs, GaInAs, and AlInAs by MBE was investigated through a study of surface morphology, R.HEED patterns, and photoluminescence. Considering growth on both nominally oriented and 2 ° mis-oriented (111)B GaAs substrates, we have found that MBE growth in the (111)B direction proceeds quite differently than (100) growth. Except in the case of high substrate temperature growth on nominally oriented (111)B substrates, the growth of (111)B GaAs and GaInAs results in films which are characterized by macroscopically rough or faceted surfaces and by weak photoluminescence. We demonstrate that the surface morphology of these macroscopically rough films may be dramatically improved by growing with modulated Ga and In fluxes. Also, we find that AlAs and Al-containing alloys grow much more smoothly than GaAs on the (111)B surface. We report an AlAs/Al.5In.5As strained MQW structure which exhibits both good surface morphology and good photoluminescence spectra. Growth mechanisms which may explain the observed differences between (111)B and (100) MBE growth are proposed.
Heteroepitaxial Growth of ImP and GaInAs on GaAs Substrates Using Tertiarybutylarsine and Tertiarybutylphosphine
Authors: Chu Shirley S. , Chu T. L. , Yoo C. H. , Smith G. L.
Published: March 2011

The heteroepitaxial growth of InP and GaInAs on GaAs substrates has been studied by using a new combination of source materials: ethyldimethylindium (EDMIn) and trimethylgallium (TMGa) or triethylgallium (TEGa) as group III sources, and tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBAs) as group V sources. The heteroepitaxial growth was carried out in a horizontal reactor in H2 under atmospheric pressure using a 2 kW quartz lamp as the substrate heater. Epitaxial InP layers of good surface morphology were obtained by using a two step process. The continuity and thickness of the buffer layer are important parameters. The InP layers deposited at 600°C are n-type, and the electron concentration decreases with decreasing TBP/EDMIn molar ratio. The 4.2 K photoluminescence of InP films is very similar to that of homoepitaxial InP films deposited at 600°C using trimethylindium (TMIn) and phosphine. Epitaxial GaxIn1–xAs layers with In composition varying from 3% to 53% have been deposltedi on GaAs substrates at 500° -550°C. A single growth step can be used for the deposition of GaxIn1–xAs with In composition of less than 20%. An InP buffer layer was used when the GaxIn1–xAS layer contains about 53% In. The composition of GaInAs was determined by optical absorption and photoluminescence techniques.
Heterostructure Nanoelectronics: A look into the Future
Authors: Barker John R.
Published: March 2011

The combination of lateral patterning techniques with refined molecular beam epitaxy methods will give considerable opportunities for the fabrication and study of extended nanostructures in the coming decade. A first target will be the understanding and exploitation of a host of quantum transport phenomena discovered in the last few years. The prospect of practicable quantum devices and circuits which utilise the coherent wave properties of the electron remains problematic but a range of new devices which exploit the Coulomb blockade is under investigation. The latter hold promise for high temperature operation and strong immunity against quantum fluctuations. The next decade should see the first exploration of the granular electronic limit in which one carrier might be expected to represent one bit of information. The granular electronic regime will provide an important arena for the resolution of fundamental controversies in quantum mechanics.
Infrared Photoconductivity and Photoluminescence from InAs/Ga1–xInxSb Strained-Layer Superlattices
Authors: Miles R. H. , Chow D. H. , Mcgill T. C.
Published: March 2011

We have examined spectrally resolved photoconductivity and photoluminescence from InAs/Ga1–xInxSb strained-layer superlattices, which have been proposed as infrared detectors in the 8-14 μm region. Our measurements indicate that the energy gaps of the strained–layer superlattices are substantially smaller than those of InAs/GaSb superlattices with similar layer thicknesses, in agreement with previous theoretical predictions. Measurements on InAs/Ga1–xInxSb superlattices with x=0 and 0.25 and layer thicknesses of 25 – 45 A indicate superlattice band gaps of 3 – 15 μm, in excellent agreement with gaps calculated by a two band k · p model. Our results demonstrate that far-infrared energy gaps are compatible with the thin layers necessary for strong optical absorption in type-IT superlattices, and suggest that InAs/Ga1–xInxSb superlattices are promising candidates for far-infrared detection.
Zinc Diffusion in GaAs-AIGaAs Heterojunction Bipolar Transistor Structures
Authors: Hobson W. S. , Pearton S. J. , Jordan A. S.
Published: March 2011

We have examined the diffusion of Zn from the base of GaAs-AIGaAs heterojunction bipolar transistor (HBT) structures during growth by organometallic vapor phase epitaxy. The role of Si doping in the emitter-contact, emitter, and collector/subcollector in enhancing the Zn diffusion has been determined by separately doping each layer. For a growth temperature of 675°C Zn shows no observable redistribution up to concentrations of 3x1019 cm−3 without Si doping. The addition of Si to the adjacent AIGaAs emitter and GaAs collector/subcollector layers causes significant diffusion from the base, while Si doping of the GaAs emitter-contact results in even greater Zn redistribution. Silicon counter-doping in the base region retards the Zn diffusion. These results are consistent with a recent model which shows that the n-type surface layer enhances the formation of gallium interstitials which diffuse into the structure and displace the Zn in the base via a kick-out mechanism.
Scanning Tunneling Microscopy Studies of GaAs Heteroepitaxial Growth on Si
Authors: Biegelsen D. K. , Bringans R. D. , Northrup J. E. , Swartz L. E.
Published: March 2011

We discuss the benefits and limitations of scanning tunneling microscopy (STM) for use in studies of the early stages of heteroepitaxy. We describe a system merging in vacuo an MBE, STM, XPS, LEED, etc. We present results for the initial stages of GaAs growth on vicinal Si(100), including As termination, Ga capping and subsequent 2D and 3D competition.
Tem Study of the Structure of Mbe GaAs Layers Grown at Low Temperature
Authors: Liliental-Weber Zuzanna
Published: March 2011

The structural quality of GaAs layers grown at 200°C by molecular beam epitaxy (MBE) was investigated by transmission electron microscopy (TEM). We found that a high crystalline perfection can be achieved in the layers grown at this low temperature for thickness up to 3 μm. In some samples we observed pyramid-shaped defects with polycrystalline cores surrounded by microtwins, stacking faults and dislocations. The size of these cores increased as the growth temperature was decreased and as the layer thickness was increased. The upper surface of layers with pyramidal defects became polycrystalline at a critical thickness of the order of 3μm. We suggested that the low-temperature GaAs becomes polycrystalline at a critical thickness either because of a decrease in substrate temperature during growth or because strain induced by excess As incorporated in these layers leads to the formation of misoriented GaAs nuclei, thereby initiating polycrystalline growth. The pyramidal shape of the defects results from a growth-rate hierarchy of the low index planes in GaAs.
Characterization of GaAs/AlGaAs Heterostructure Quantum Wells by Microwave Absorption
Authors: Zappe Hans P. , Jantz Wolfgang
Published: March 2011

Magnetic-field-dependent microwave absorption Is shown to be a useful non-destructive and contact-free technique to study transport behavior in GaAs/AlGaAs devices. It allows quick measurement of resistance, mobility and carrier concentration in the two-dimensional electron gas of heterostructure quantum wells. The two and three dimensional conductivities may be separately evaluated allowing detailed study of conduction in the active layer of high electron mobility (HENT) devices. Applications of the approach to examination of device structural dependencies, carrier-density conduction behavior and the effects of etch processing on quantum well integrity are presented.
High Quality GaAs on Si by Selective Area Epitaxy
Authors: Karam N.H. , Haven V. , Vernon S.M. , El-Masry N. , Lingunis M. , Haegel N.
Published: March 2011

Selective area Epitaxy (SE) of high quality GaAs on Si films has been achieved using conventional MOCVD and Atomic Layer Epitaxy (ALE) nucleation techniques. Epitaxial GaAs films were deposited inside windows etch patterned in the oxide coated Si wafers. SE was found to eliminate wafer warpage, reduce film cracking and reduce the tensile stresses for islands less than 200 µm/side. Complete stress relief has been achieved in 10 µm/side islands after oxide removal. Defect reduction techniques have been employed resulting in two orders of magnitude reduction in the dislocation density and excellent surface morphologies. This paper addresses the potential of SE, by the above techniques in improving the quality of the GaAs on Si films.
Mbe Growth and Characterization of Hgcdte Heterostructures
Authors: Koestner R.J. , Goodwin M.W. , Schaake H.F.
Published: March 2011

HgCdTe heterostructures consisting of a thin n-type widegap (250 meV or 5 μm cutoff) layer deposited on an n-type narrowgap (100-125 meV or 10-13 μm cutoff) layer offer the promise of very high performance metal-insulator-semiconductor (MIS) photocapacitors for long wavelength infrared (LWIR) detection. Molecular Beam Epitaxy (MBE) is a candidate growth technology for these two layer films due to its fine control in composition, thickness and doping concentration. The critical materials issues are reducing the defect content associated with twins in the grown layers, achieving low net donor concentrations in the widegap layer, and avoiding the formation of misfit dislocations at the HgCdTe heterointerface. This paper will report on our recent progress in these directions.
Explanation of Observed P-Type Conductivity in Movpe ZnSE/GaAs Heterostructures
Authors: Briot O. , Cloitre T. , Tempier N. , Sauvezon R. , Averous M. , Aulombard R.L.
Published: March 2011

Together with the advanced growth technologies of zinc selenide epitaxial films by MOVPE or MBE, severals workers have reported the observation of p-type conductivity in this material. However, there are some inconsistencies in most of the papers reporting such results.

We report here the MOVPE crystal growth of nominaly undoped ZnSe/GaAs S.I. layers using alkyls as precursors, and their optical and electrical characterizations. We show the possibility to observe p-type conductivity in ZnSe due to a hole accumulation at the interface in the GaAs side. This is consistent with a simple model taking Into account the conduction and valence bands discontinuities at the ZnSe/GaAs interface.
Optical Investigation of the Band Offset of CdxZn1−xTe /ZnTe and ZnSexTe1−x/ZnTe Superlattices
Authors: Rajakarunanayake Y. , Phillips M. C. , Mccaldin J. O. , Chow D. H. , Collins D. A. , Mcgill T. C.
Published: March 2011

We have analyzed photoluminescence spectra from CdxZnl−xTe /ZnTe and ZnSexTel−x/ZnTe strained layer superlattices grown by MBE, and obtained the band offsets by fitting to theory. We find that the valence band offset of the CdTe/ZnTe system is quite small (-50± 160 meV). In CdxZnl−xTe /ZnTe superlattices, the electrons and heavy holes are confined in the CdxZn1−xTe layers (type I), while the light holes are confined in the ZnTe layers (type II). On the other hand, the photoluminescence data from the ZnSexTe1−x /ZnTe superlattices suggest that the band alignment is type II, with a large valence band offset (−907 ± 120 meV). We also investigated the band bowing in the ZnSexTel−x alloys by optical spectroscopy, and found that there is only a small component of bowing in the valence band, while most of the bowing occurs in the conduction band. Based on our results for band alignments, we evaluate the prospects for minority carrier injection in wide bandgap heterostructures based on ZnSe, ZnTe, and CdTe.
Growth and Characterization of Znsete Epilayers and Superlattices
Authors: Phillips M. C. , Rajakarunanayake Y. , Mccaldin J. O. , Miles R. H. , Chow D. H. , Collins D. A. , Mcgill T. C.
Published: March 2011

Little has been published about Te-rich ZnSexTel−x grown at low temperatures, in spite of some successes in the fabrication of wide band gap light emitting devices from ZnSeTe alloys grown at higher temperatures. We present x-ray diffraction and photoluminescence (PL) spectra for ZnSeTe epilayers and ZnSeTe/ZnTe superlattices grown by molecular beam epitaxy (MBE). These we compare with measurements on ZnTe, ZnSe and CdZnTe epilayers and on CdZnTe/ZnTe superlattices grown under similar conditions and also with data published for ZnSeTe alloys grown at high temperatures. Equilibrium phase diagrams for the ZnSeTe alloy system suggest a large miscibility gap at MBE growth temperatures; this may account for some unusual features in the (PL) spectra and for large line widths in the x-ray data. In spite of these possible miscibility problems, we find that ZnSeTe alloys luminesce brightly.
Xps and Aes Studies of the Initial Stage of CdTe Growth on (100) GaAs by Movpe
Authors: Ekawa Mitsuru , Yasuda Kazuhito , Sone Syuji , Sugiura Yoshiyuki , Saji Manabu , Tanaka Akikazu
Published: March 2011

XPS and AES analyses were performed to investigate the initial growth mechanism and the selection of the growth orientations of CdTe layers grown on (100) GaAs substrates by MOVPE. The (100) CdTe growth was reproducibly achieved when the GaAs surface was completely covered by one monolayer of Te before the growth, otherwise (111) growth occurred.
Properties of IV-VI Narrow Gap Semiconductors on Fluoride Covered Silicon
Authors: Zogg H. , Maissen C. , Blunier S. , Masek J. , Meyer V. , Pixley R.E.
Published: March 2011

We present new results on structural and electronic properties of epitaxial lead chalcogenides on Si-substrates. A stacked MBE-grown CaF2/BaF2 buffer of 200 nm thickness serves to overcome the large lattice- and thermal expansion mismatches. Lead chalcogenide layers are grown by MBE or HWE with thicknesses of a few μm.

The X-ray rocking curve widths of these layers are below 200 arc sec. They are as low as curve widths of similar layers grown on bulk BaF2, or GaAs layers of comparable thicknesses on Si. The mechanical strain-state of the layers was determined with x-ray measurements and RBS channelling angular scans. Strain is below 4.10−4 at room temperature, indicating a near complete relaxation of the thermal and lattice misfit induced strains.

The quality of the layers is sufficient to integrate whole photovoltaic IR-sensor arrays.

We have fabricated linear arrays with cut-off wavelengths of 12 μm by using Pb1−xSnxSe, 5 μm with PbTe, and 3 - 4 gm with PbS and Pb1−xEuxSe. The structures withstand repeated cooling to the 80K operation temperature.
Disilane Adsorption on Ge(111): A Multiple Internal Reflection Infrared Spectroscopy Study
Authors: Crowell John E. , Lu Guangquan
Published: March 2011

The adsorption and decomposition of disilane on the Ge(111) surface has been investigated using multiple internal reflection infrared spectroscopy (MIRIRS). At temperatures ≤ 110 K, Si2H6 weakly bonds to the Ge surface in a molecular fashion. Upon mild heating to temperatures between 110 - 150 K, both desorption and dissociation occur. Dissociative adsorption also occurs upon exposure at temperatures > 110 K. Molecular adsorption is no longer observed for exposure at temperatures above 150 K. Detection of the low frequency deformation modes provides direct evidence for dissociation of the Si-Si bond between 120 - 150 K. The primary species present at 150 K is silyl, SiH3. Si-H bond scission takes place from 150 - 500 K, resulting in GeH formation. Production of SiH2 and SiH is spectroscopically identified in this temperature range.
Epitaxial Growth and Stability of C49 TiSi2 ON Si(111).
Authors: Jeon Hyeongtag , Honeycutt J. W. , Sukow C. A. , Humphreys T. P. , Nemanich R. J. , Rozgonyi G. A.
Published: March 2011

Epitaxial TiSi2 films have been grown by molecular beam epitaxy (MBE) on atomically clean Si(111)-orientated substrates. The growth procedure involves the ambient temperature deposition of Ti films of 50Å thickness and annealing to 800°C. In situ low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) techniques have been used to monitor the TiSi2 formation process. The epitaxial films have been identified as the C49 metastable phase by both Raman spectroscopy and electron diffraction. Plan view transmission electron microscopy shows three different connected island morphologies. The individual island structures are single crystal and are grown epitaxially with different crystallographic orientations. The orientational relationship of the largest islands is given by [3 1 1] C49 TiSi2//[112]Si and (130) C49 TiSi2//(l1 1)Si. High resolution transmission electron microscopy (HRTEM) cross-section shows a coherent interface extending over several hundred angstroms.
Specimen Preparation of Thin Crystalline Fibers for Transmission Electron Microscopy
Authors: Koch Rosemarie , Marshall Ann F.
Published: March 2011

A technique was developed to prepare crystalline fibers of less than 1 mm diameter for transmission electron microscopy. Cross sections were made by casting a short piece of the fiber in an epoxy resin, sectioning the block, and laminating the slices against thin glass discs for stability before dimpling. Longitudinal sections were reinforced in a similar manner. TEM tungsten rings were sometimes used as an alternative method to add stability to the longitudinal sections. The technique was especially developed for Bi-Sr-Ca-Cu-O compounds but is also suitable for other materials.
Preparation of TEM Specimens of Rubber Modified Polymeric Materials by Ultramicrotomy and OsO4 Staining
Authors: Yegnasubramanian S.
Published: March 2011

This paper presents the specimen preparation approaches developed to image rubber(butadiene) - modified epoxy polymeric materials used in the microelectronics industry by TEM. The methodology is complicated by the fact that silica and calcium carbonate (>75 wt%) are used as filler materials while the rubber is used as a toughening agent in the samples investigated.
Cross-Sectional TEM Specimen Preparation of Semiconductor Devices by Focused Ion Beam Etching
Authors: Park Kyung-ho
Published: March 2011

A procedure for preparing cross-sectional TEM specimens by focused ion beam etching (FIB) of specific regions on an integrated circuit chip is outlined. The investigation of the morphology, structure and local chemistry of precisely selected regions of semiconductor devices becomes increasingly important since the lateral dimensions and layer thickness of device structures are continually being reduced. The standard technique of preparing specimens for TEM, whether planar or cross-sectional, cannot select particular small regions. Some techniques and a number of tools and fixtures have been proposed which allow us to prepare TEM specimen of prespecified locations in complex devices. Most of these techniques, however, are still very difficult, tedious process and time consuming.

A new technique has been proposed recently involving the use of FIB. The technique ensures that the preselected area of submicron scale will be located in the electron transparent section used for TEM imaging, in preparation turn-around time of about two hours. The TEM imaging of specific contacts via hole in a VLSI chip is illustrated.
Preparation of Planar and Cross-Sectional Thin Specimens by Chemical Dimpling with Optically Controlled Terminator
Authors: Hwang D. M. , Nazar L. , Chen C. Y.
Published: March 2011

We have modified a conventional dimpling machine to perform chemical polishing with a reactive etchant. The modified dimpler also detects specimen perforation in situ optically, and automatically stops the dimpling process by lifting the dimpler wheel and flooding the specimen with a rinse solution. Using this apparatus, we are able to prepare both planar and cross-sectional thin specimens of compound semiconductor materials without using expensive and time-consuming ion-milling. The specimens have large thin areas, are free of artifacts, and are suitable for high-resolution lattice imaging.
Electron Paramagnetic Resonance in Semiconductors
Authors: Corbett James W. , Kleinhenz Richard L. , Wilsey Neal D.
Published: March 2011

The use of electron paramagnetic resonance (EPR) in the study of defects in semiconductors is briefly reviewed, including group IV (C-diamond, Si, Ge, SiC), III-V (AlSb, GaAs, GaSb, GaP, InAs, InP, InSb), II-VI (BaO, BaS, BeO, CaO, CaS, CaSe, CdO, CdS, CdSe, CdTe, MgO, SrO, SrS, ZnO, ZnS, ZnSe, ZnTe) and miscellaneous svstems. The identification of defects via EPR is described as is the exploitation of that identification as a tool in future studies. Particular attention is paid to Si, where is emerging an integrated panorama of identified defects ranging from point defects to aggregates through intermediate defect configurations (as discussed by Tan) to dislocations and stacking faults; EPR results in Si as a testing ground for the theory of shallow donors, in the understanding of diffusion at high temperatures and in the study of heat-treatment defects are discussed as examples of the use of EPR as a tool in defect studies.
Undissociated Dislocations and Intermediate Defects in as+ Ion Damaged Silicon
Authors: Foell H. , Tan T. Y. , Krakow W.
Published: March 2011

Undissociated dislocation dipoles and intermediate defects are detected in As+ ion damaged Si using the lattice resolution technique of transmission electron microscopy. The present results are consistent with our proposed dislocation nucleation models.
Negative-U Properties for Point Defects in Silicon
Authors: Watkins G. D.
Published: March 2011

A defect has negative-U properties if it can trap two electrons (or holes) with the second bound more strongly than the first. It is as if there were a net attraction between the two carriers (negative Hubbard correlation energy U) at the defect, and the defect energy levels in the gap are therefore inverted from their normal order. Experimental evidence is presented that interstitial boron and the lattice vacancy, both common simple point defects produced by electron irradiation of silicon, have this unusual property. These defects represent the first and only concrete examples of negative-U centers in any material and serve as models for an understanding of the phenomenon.
Electronic and Mechanical Properties of Dislocations in Semiconductors
Authors: Hirsch P B
Published: March 2011

It has been known for some time that the velocity of dislocations in semiconductors depends strongly on the concentration of electrically active impurities. Various explanations based on different models of the electronic structure of the dislocations have been proposed; they involve the dependence of the formation energy and/or activation energy of migration of dislocation kinks on the Fermi level. A review will be presented of these theories and of recent structural models of dislocation cores and kinks.
Characterization of Dislocations and Interfaces in Semiconductors by High Resolution Electron Microscopy
Authors: Spence J.C.H. , Olsen A.
Published: March 2011

It is not presently possible to resolve the individual atoms in any semiconductor by high resolution electron microscopy (HREM). However symmetry arguments may be used to allow near-atomic resolution lattice images to be interpreted in rare favorable cases. This method is applied to the problem of distinguishing shuffle and glide set partial dislocations in silicon. It is also proposed that two dimensional characteristic loss energy selected diffraction patterns be used to reveal the local symmetry about selected substitutional species implanted in semiconductor lattices.
Defect Structure of the Epitaxial Pd2 Si-Silicon Interface
Authors: Cherns D. , Smith D.A.
Published: March 2011

The crystallography of the epitaxial Pd2 Si-silicon interface has been analyzed with special reference to the character of interfacial dislocations. It is proposed that the Pd2 Si which forms at the interface does so by the diffusion stimulated glide of transformation dislocations.
From the Mystery to the Understanding of the Self-Interstitials in Silicon
Authors: Frank W. , Seeger A. , Gösele U.
Published: March 2011

Our present knowledge on self-interstitials in silicon and the rôle these defects play under widely different experimental conditions are surveyed. In particular, the following phenomena involving self-interstitials either in supersaturations or under high-temperature thermal-equilibrium conditions are considered: mobility-enhanced diffusion of self-interstitials below liquid-helium temperature, thermally activated diffusion of self-interstitials at inter-mediate temperatures (14O K to 600 K), concentration-enhanced diffusion of Group-III or Group-V elements in silicon at higher temperatures, and— as examples for high-temperature equilibrium phenomena — self-diffusion and diffusion of gold in silicon. This leads to the picture that the self-interstitials in silicon may occur in different electrical charge states and possess dumbbell configurations or are extended over several atomic volumes at intermediate or high temperatures, respectively.
The Effect of Annealing Temperature on the Morphology of Stacking Faults in Czochralski Silicon
Authors: Pinizzotto R. F. , Schaake H. F.
Published: March 2011

Nucleation and growth of stacking faults formed in CZ silicon during oxygen precipitation have been studied using x-ray topography, TEM and FTIR. Samples were annealed in argon for various times at 550°C and 750°C followed by a 16 hour anneal in dry oxygen at 1000°C. In samples annealed at 550°C, the stacking faults were several layers thick with colonies of precipitates at their centers. The faults in samples annealed at 750°C contained only one particle and were single in nature. It is proposed that the faults are formed by thin oxygen precipitate platelets and that the different morphologies are due to different oxygen precipitation rates. The platelets are probably a modified cristobalite, as determined by micro-diffraction results.
Electron Microscope Characterization of Pulse Annealed Semiconductors
Authors: CULLIS A. G.
Published: March 2011

The pulse processing techniques that have assumed prominence over the past few years offer various important advantages for device fabrication technology. However, the usefulness of each individual method depends substantially upon the specific annealing mechanism involved. This article demonstrates the role of electron microscopy in elucidating such mechanisms and in analysing annealed semiconductor structures of importance to both research workers and semiconductor technologists. The range of laser and electron beam pulse annealing methods is covered and defect structure transitions observed are related to the solid and liquid phase processes occurring. Characteristic impurity trapping and segregation phenomena are described.
Melting and Laser Annealing in Semiconductors using 0.485 μm and 0.193 μm Pulsed Lasers
Authors: Narayan J. , Fletcher J. , Eby R. E.
Published: March 2011

Annealing of displacement damage, the dissolution of boron precipitates, the formation of constitution supercooling cells, and the broadening of dopant profiles have been studied in laser annealed silicon. These samples were irradiated with a dye laser (λ = 0.485 µm, τ = 9 ns, E = 0.7–1.2 J cm−2) and an Excimer laser (λ = 0.193 µm, τ= 9 ns, E = 0.5–0.7 J cm−2) pulses. These results can be consistently interpreted by invoking melting during pulsed laser irradiation. Thus these results provide convincing evidence for the melting phenomenon.
Residual Defects after Pulsed Laser Annealing of Ion implanted Silicon
Authors: Mesli A. , Muller J.C. , Salles D. , Siffert P.
Published: March 2011

Capacitance transient spectroscopy has been used to investigate the electrically active defects subsisting, after a ruby laser pulse annealing, in ion implanted silicon. In contrast to the common view, it is shown that the identified point defects are related to residual implantation related defects buried beyond the dopant distribution and not to the laser effect.
Effect of Electric Field and Current Injection on the Main Electron Trap in Bulk GaAs
Authors: Makram–Ebeid S.
Published: March 2011

The dark capacitive transients related to the main electron trap in bulk and VPE GaAs have been studied in detail. The low temperature low field transients are induced by electrons injected from the metal counter electrode. Both hot electron capture and impact ionization effects are observed. At high fields, a phonon assisted tunneling model accounts for the observations and yields the values of the Franck Condon Shift Sw and the energy w of the phonon coupled to the level. These values are found to be in good agreement with other independent estimates.
Imaging of Defects in Cadmium Telluride using High Resolution Transmission Electron Microscopy
Authors: Ponce F. A. , Yamashita T. , Bube R. H. , Sinclair R.
Published: March 2011

The defect structure of cadmium telluride has been investigated using high resolution transmission electron microscopy. The variation of the TEM images with the defocus value is discussed, and defect symmetry considerations are used to correlate the image contrast characteristics with the lattice struc ture. Experimental micrographs of stacking faults and dislocations in the structure are analyzed.
A Channeling Study of Defect-Boron Complexes in Si
Authors: Swanson M.L. , Howe L.M. , Saris F.W. , Quenneville A.F.
Published: March 2011

Si crystals were doped with 0.1–0.2 at% 11B in the near surface region by ion implantation followed by thermal diffusion at 1373 K or by ruby laser annealing. The position of the B atoms in the Si lattice was determined by channeling measurements, utilizing both the yield of H+ ions (of incident energy 0.7 MeV) backscattered from Si atoms and the yield of alpha particles from the 11B(p,α)8Be nuclear reaction. Initially, 95–99% of the B atoms were substitutional. Irradiation at 35 K or 293 K with 0.7 MeV H+ displaced B atoms from lattice sites. The displacement rate was greater at 293 K than at 35 K, and was greater for diffused samples than for laser annealed samples. Following 35 K irradiations, a large increase in the fraction fdB of displaced B atoms occurred during annealing near 240 K. At higher annealing temperatures, fdB decreased over a broad temperature range from 425–825 K. Angular scans through <110> channels for the laser annealed samples after 293 K irradiation or after 35 K irradiation plus 293 K annealing showed a pronounced narrowing of the dip in 11B(p,α)8Be yields compared with the dip in yields from Si, whereas no narrowing was observed for <100> channels. These results indicate that B atoms were displaced into specific lattice sites by the migration of an interstitial B defect (the EPR G28 defect) near 240 K.
Electronic Structure of Graphite Intercalation Compounds
Authors: Holzwarth N.A.W. , Louie Steven G. , Rabii Sohrab
Published: March 2011

In this paper we present a brief survey of previous work as well as some new preliminary results for graphite fluoride compounds.
Fermi Surface and Charge Density Waves in Second-Stage Graphite-Bromine Intercalation Compounds
Authors: Batallan F. , Rosenman I. , Simon Ch. , Furdin G.
Published: March 2011

Results of de Haas van Alphen effect study on second-stage bromine graphite intercalation compound C14 Br are presented together with a two dimensional model of electronic structure and Fermi surface. The results are characterized by a mixing of de Haas-van Alphen frequencies. The nature of the coupling mechanisms between orbits is discussed. It is shown that the two dimensional Fermi surface of C14 Br contains nested parallel parts which can stabilize charge density waves. A comparison between the nesting vectors of this Fermi surface and the satellites and diffuse streaks found in structural studies shows a fair agreement between both.
Thermal Transport in Intercalated Graphite
Authors: Issi J-P.
Published: March 2011

Recent results on the temperature and stage dependence of the thermal conductivity of various graphite intercalation compounds are reported and briefly analyzed. In the lowest temperature range the in-plane thermal conductivity which is mainly electronic, is higher than that of pristine graphite. Around room temperature, in spite of an increased electronic conduction, a decrease in the total thermal conductivity relative to pristine graphite is observed. This shows that the dominant effect is the decrease of the lattice contribution due to increased phonon scattering by lattice defects. The c-axis conduction is attributed entirely to phonons and the anisotropy ratio is of order of 102 in the liquid helium range and increases up to several hundreds around room temperature. Some results on the temperature variation of the in-plane and c-axis thermopower for donor and acceptor compounds are also presented and discussed.