bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of NEV Au++ implanted silicon
Authors: Alford T.L. , Theodore N.D. , Mayer J.W. , Carter C.B. , Cheung N.W. 
Published: June 2020

There has recently been increasing use of MeV ion beams for materials modification. When compared to more common lower, keV-energy implantation, MeV-ion irradiation has a broader variation in the type of damage along the ion path. This is because of the more significant difference between damage and range distributions in the case of MeV implants as opposed to keV implants. Previous works showed that MeV-implanted Si-ions react differently with various types of lattice damage in silicon; interactions range from simple point-defect annihilation to the formation of extended defects. Earlier investigations of Au implanted into previously amorphized silicon have observed Au segregation as a result of its being expelled from the recrystallizing amorphous layer during ion-beam irradiation. In this study, the interaction of MeV Au++ atoms with the different types of damage produced along the MeV-ion beam path is investigated.Silicon (100) single crystal wafers were given a HF dip and were then mounted on a copper sample stage; the stage functions as a heat-sink. The stage together with the specimen was then placed in a Tandem ion-implanter. The specimens were implanted with gold; implant-energies varied from 1.8 - 4.4 MeV and fluences ranged between 0.1 - 10×1016 Au++/cm2.
Cross-sectionnal Electron Microscopy investigation of silicon amorphisation during high temperature zinc-ion bombardment
Authors: Faure J. , Simov S. , Balossier G. , Bharadwaj L.M. , Claverie A. , Bonhomme P. 
Published: June 2020

In silicon technology, the use of zinc as a dopant reveals a great interest in optoelectronic device fabrication, such as photoresistors, light amplifiers, photodiodes etc. Recently, zinc implantation has received a new attention in thermal oxidation of silicon. Oxidation kinetics are strongly correlated to zinc segregation at the oxide-silicon interface and to the nature of the ion induced damage which is stable at the implantation temperature. We used cross-sectionnal electron microscopy (XTEM) for the characterisation of the structural modifications induced in a monocrystalline silicon substrate during high temperature Zn+implantation. During irradiation, silicon wafers (111 oriented) were heated to 110°C by use of a resistively heated copper block, while the incident ion beam had an energy of 120keV and a current density less than 3μA.cm-2.Figure 1 presents the effect of Zn+ implantation associated with a 1014 ions.cm-2 implanted dose. This 220 DF image reveals, in black, a buried noncrystalline layer lying from about 30 to 85nm from the arrowed silicon surface.
Defect morphology in thick relaxed layers of InGaAs on GaAs
Authors: Dixon R H , Kidd P , Goodhew P J 
Published: June 2020

Thick relaxed InGaAs layers grown epitaxially on GaAs are potentially useful substrates for growing high indium percentage strained layers. It is important that these relaxed layers are defect free and have a good surface morphology for the subsequent growth of device structures.3μm relaxed layers of InxGa1-xAs were grown on semi - insulating GaAs substrates by Molecular Beam Epitaxy (MBE), where the indium composition ranged from x=0.1 to 1.0. The interface, bulk and surface of the layers have been examined in planar view and cross-section by Transmission Electron Microscopy (TEM). The surface morphologies have been characterised by Scanning Electron Microscopy (SEM), and the bulk lattice perfection of the layers assessed using Double Crystal X-ray Diffraction (DCXRD).The surface morphology has been found to correlate with the growth conditions, with the type of defects grown-in to the layer (e.g. stacking faults, microtwins), and with the nature and density of dislocations in the interface.
Cross-sectional Transmission Electron Microscopy of (AlAs)15(InAs)1 Superlattices
Authors: Ballesteros C. , Piqueras J. , Vázquez M. , Silveira J.P. , González L. , Briones F. 
Published: June 2020

Multibeam and bright field transmission electron microscopy are used to determine the structure of (InAs)1/(AlAs)15 superlattices. The interest of InAs/AlAs system arises from the large gap difference. The main problem in the obtention of strained layer superlattices (SLS), with a large lattice mismach, 7% is that of controlling the growth process to obtain high quality layers with sharp interfaces.A modification of the conventional MBE technique, Atomic Layer Molecular Beam Epitaxy (ALMBE) seems to be very appropiate for the growth of such strained layer structures. In particular, high quality layers of materials that demand different growth conditions by MBE, like InAs and AlAs can be obtained at a common low substrate temperature (350-400°) by ALMBE due to the ability to force 2D or layer by layer nucleation and growth. Present superlattices are part of a series with structure (AlAs)15/(InAs)n (n = 1, 2, 3 and 5 ml) whose study by HREM is under way in order to determine critical thickness limits.
Direct observation of strain distribution in InP/In1−xGaxP heterointerfaces by CAT method
Authors: Kakibayashi Hiroshi , Nagata Fumio , Itoh Kazuhiro 
Published: June 2020

The characteristics of electronic and optical devices, which have been developed utilizing a strained superlattice composed of multilayered structure accommodating lattice mismatch, are considerably affected by the strain distribution at the heterointerfaces. It has been, however, very difficult to measure the nanometer areas due to poor spatial resolution of the usual evaluation methods such as X-ray diffraction, Raman scattering, photoluminescence.The authors proposed a new transmission electron microscopy based on the compositional analysis by thickness-fringe (CAT) which was successfully applied for evaluating the compositional profiles in GaAs/AlxGa1−xxAs superstructures with a high spatial resolution of 0.4 nm. In this study, the CAT method is applied to evaluate the strain distribution with high spatial resolution and sensibility. The intensity distribution of the thickness fringe is affected not only by the composition but also by the Bragg conditions of electron diffraction. The lattice planes near the heterointerface bend due to the lattice distortion between two crystals with different lattice constant. The change of Bragg condition at the bent plane can be detected in the CAT image as the shift of thickness fringe.
Residual damage after annealing of Be and O implanted GaAs/AlGaAs hetero bipolar transistors
Authors: Wurzinger P. , Oppolzer H. , Pongratz P. , Skalicky P. 
Published: June 2020

Beryllium (2.5·1014/cm2 at 40 keV and 7.5·1014/cm2 at 90 keV) and oxygen (1013/cm2 at 380 keV) were implanted into a GaAs/AlGaAs-HBT (hetero bipolar transistor) to facilitate the formation of an ohmic contact with the p-type base using planar technology. The layer sequence and doping levels of the HBT are listed in table 1. Annealing was performed using optical RTA (rapid thermal anneal) equipment, at 860 °C, for 3 s. Technological data as well as SIMS, electrical, and photoluminescence measurements are published in detail elsewhere. This paper focuses on the residual lattice damage in the annealed HBT. TEM investigations were performed at 200 keV beam voltage using cross-sectional specimens.Fig.l shows a dark-field micrograph taken with a {200} reflection. The different layers are numbered (cf. table 1) and can be distinguished by differences in overall contrast. The residual damage consists of Frank type (b=a/3<111>) and perfect(b=a/2<110>) dislocation loops. The perfect loops are prismatic. Most of them lie in the <110> plane perpendicular to the Burgers vector b. All loops are of interstitial type. Defects are only found in the top three layers of the HBT which corresponds to the depth of the Be implantation. The defect distribution is inhomogeneous (Fig.1): While there are rather large loops (up to 200 nm) together with small ones in the GaAs layers of cap and base, only small loops (up to 30 nm) can be observed in the AlGaAs emitter layer.
A study of the interaction of silver with amorphous chalcogenide films in the Scanning Electron Microscope
Authors: Fitzgerald A.G. , Potrous S.M. 
Published: June 2020

The diffusion of silver in amorphous chalcogenides is the basis for high-resolution lithographic applications. Previous studies of the diffusion of silver on contact with chalcogenide films has been studied by Auger depth profiling and the effects of photodoping on chemical bonding have been studied by x-ray photoelectron spectroscopy. Electron lithographic effects have been studied in the transmission electron microscope.The objective of the investigation described here has been to determine the degree of diffusion of silver in the amorphous chalcogenides, As2S3, As2Se3, GeS and GeSe when these films are in contact with thin silver films. The silver distribution has been determined by x-ray microanalysis of film cross-sections in the scanning electron microscope (SEM). Electron beam induced conductivity (EBIC) at points in these films has also been investigated.
Chemical structure of diamond-like carbon thin films
Authors: Cho N.-H. , Krishnan K.M. , Bogy D.B. 
Published: June 2020

Diamond-like carbon (DLC) films have attracted much attention due to their useful properties and applications. These properties are quite variable depending on film preparation techniques and conditions, DLC is a metastable state formed from highly non-equilibrium phases during the condensation of ionized particles. The nature of the films is therefore strongly dependent on their particular chemical structures. In this study, electron energy loss spectroscopy (EELS) was used to investigate how the chemical bonding configurations of DLC films vary as a function of sputtering power densities. The electrical resistivity of the films was determined, and related to their chemical structure.DLC films with a thickness of about 300Å were prepared at 0.1, 1.1, 2.1, and 10.0 watts/cm2, respectively, on NaCl substrates by d.c. magnetron sputtering. EEL spectra were obtained from diamond, graphite, and the films using a JEOL 200 CX electron microscope operating at 200 kV. A Gatan parallel EEL spectrometer and a Kevex data aquisition system were used to analyze the energy distribution of transmitted electrons. The electrical resistivity of the films was measured by the four point probe method.
A TEM study of discommensurations in K2ZnCl4
Authors: Pan Xiaoqing 
Published: June 2020

A number of A2BX4-type compounds are known to have an incommensurate (INC) phase between high temperature paraelectric phase (space group Pcmn) and low temperature ferroelectric commensurate (C) phase (space group Pc21n). In the case of Rb2ZnCl4 the static patterns of discommensurations (DCs) and some information about their kinematic behavior have been revealed by transmission electron microscopy (TEM). More recently the DCs in the C-phase of K2ZnCl have been studied by TEM as well as by replica techique Here we report our observation of DCs in K2ZnCl4Single crystals of K2ZnCl4 were grown from a stoichiometric mixture of aqueous solutions of KCL and ZnCl2 at about 40°C. The crystal plates were cut using a wet thread, and were further thinned
by Ar ion sputtering. Observations were carried out with a JEOL-200CX electron microscopy at an accellarating voltage of 200kV, using a liquid nitrogen cooling holder.
Effects of dopant concentration on the microstructure of tin- doped indium oxide thin films
Authors: Rauf I. A. 
Published: June 2020

To understand the electronic conduction mechanism in Sn-doped indium oxide thin films, it is important to study the effect of dopant atoms on the neighbouring indium oxide lattice. Ideally Sn is a substitutional dopant at random indium sites. The difference in valence (Sn4+ replaces In3+) requires that an extra electron is donated to the lattice and thus contributes to the free carrier density. But since Sn is an adjacent member of the same row in the periodic table, the difference in the ionic radius (In3+: 0.218 nm; Sn4+: 0.205 nm) will introduce a strain in the indium oxide lattice. Free carrier electron waves will no longer see a perfect periodic lattice and will be scattered, resulting in the reduction of free carrier mobility, which will lower the electrical conductivity (an undesirable effect in most applications).One of the main objectives of the present investigation is to understand the effects of the strain (produced by difference in the ionic radius) on the microstructure of the indium oxide lattice when the doping level is increased to give high carrier densities. Sn-doped indium oxide thin films were prepared with four different concentrations: 9, 10, 11 and 12 mol. % of SnO2 in the starting material. All the samples were prepared at an oxygen partial pressure of 0.067 Pa and a substrate temperature of 250°C using an Edwards 306 coating unit with an electron gun attachment for heating the crucible. These deposition conditions have been found to give optimum electrical properties in Sn-doped indium oxide films. A JEOL 2000EX transmission electron microscope was used to investigate the specimen microstructure.
Electron Microscope contrast mechanisms of doped semiconductor layers
Authors: Perovic D.D. , Weatherly G.C. 
Published: June 2020

With the development of crystal growth techniques such as molecular beam epitaxy, it is now possible to fabricate modulation-doped superlattices consisting of alternating, ultra-thin layers of n- and/or p-type material abruptly separated by undoped material. At sufficiently high dopant concentrations it has been found that these atomically abrupt layers can be readily imaged in the transmission electron microscope. This study is concerned with the visibility of boron and arsenic-doped layers in silicon from which a generalized interpretation of the TEM contrast of doped layers can be obtained.Fig.l is a cross-sectional, two-beam dark field image of a B-doped superlattice consisting of five three-layer sets. Each three-layer set was grown using a different substrate temperature in the range 600 to 800 °C; the boron occupies substitutional positions in the Si lattice at the lower temperatures while at the higher temperatures the boron has precipitated in stable clusters (∽3nm) as observed by direct lattice imaging. The maximum concentration of boron in all layers is ≈ 0.7 at.% which is well above the solid solubility limit at these temperatures. There are several important contrast features to note in Fig. 1. First, in the thicker areas of the foil where anomalous absorption effects are dominant, the B-doped layers appear dark relative to the Si matrix; the same is true in bright field.
The interaction of electron beams with solids - Some new effects
Authors: Humphreys C J , Bullough T J , Devenish R W , Maher D M , Turner P S 
Published: June 2020

It has recently been found that electron beams, of energy typically 100 keV, can damage a very wide range of solids, many of which are normally thought to be stable to electron irradiation. For example, metals, semiconductors and ceramics can all be damaged by electrons having energy less than that required for direct displacement damage. Radiation damage effects are particularly apparent when using intense electron beams from field emission guns in STEM's, TEM's and SEM's, but damage also occurs in materials thought to be stable when using electrons from LaB6, or heated W filaments. Considerable care must therefore be taken in microanalysis, etc, particularly when using field emission guns.If the incident electron beam is focussed to nanometre-scale diameter, then nanometre-scale surface and volume structures (e.g. indentations, holes and lines) can be produced in a variety of specimens. It is also possible to cut a specimen to a desired shape with nanometre precision and to remove surface steps from surfaces, leaving them atomically smooth.
Some examples of ruthenium tetroxide staining technique for TEM of polymers
Authors: Heckmann W. 
Published: June 2020

Staining is essential for examination of polymers under the electron microscope. Organic polymers consist exclusively of light atoms, e.g. carbon, oxygen, hydrogen and nitrogen, with the consequence that natural contrast is faint and completely inadequate. The aim of staining is to treat the polymer molecules with chemical substances, which must contain heavy atoms, and thus to modify them so that the electron density is drastically increased on the molecular site. Frequently, a hardening and structure-stabilizing effect is also achieved.In the last few years, ruthenium tetroxide staining has developed into a very useful method. Ruthenium tetroxide (RuO4) is a very strong oxidizing agent that can react not only with unsaturated, but also with many saturated polymers. For this reason, the method is less selective than others, yet it attracts interest for some polymer systems, because it allows differences in the rate of reaction and reaction intensity between various polymers to be exploited. This will be explained in the light of a few examples.
Correlative STM, FESEM, and TEM studies of fibrillar structures in liquid crystalline polymers
Authors: Musselman I. H. , Russell P.E. , Chen R.T. , Jamieson M.G. , Sawyer L.C. 
Published: June 2020

Hierarchical fibrillar structures have been reported to be present in liquid crystalline polymer (LCP) extrudates such as fibers and tapes. Using conventional scanning and transmission electron microscopy (SEM, TEM), the smallest fibrils were shown to be about 50 nm wide and 5 nm thick. With the emergence of higher resolution imaging techniques such as scanning tunneling microscopy (STM) and field emission SEM (FESEM), we have been able to further explore the ultrastructures in the LCP fibrils and extend the LCP structural model.The LCP materials investigated consist of copolyesters of 4-hydroxybenzoic acid (HBA) and 2- hydroxy-6-napthoic acid (HNA) in the form of melt-spun fibers and extruded tapes. These materials exhibit unidirectionally-oriented structures as revealed by x-ray diffraction and microscopy studies. For STM and FESEM, samples were prepared by a peel-back method which reveals the internal structures of fibrils. In addition, ultrasonication was used to disintegrate the LCP fibers and tapes to provide fine “fibrillar” samples for STM, FESEM, and TEM studies. The original tape and fiber surfaces were also examined by STM and FESEM. Thin Pt coatings (ca. 5 nm) were deposited on the LCP samples using ion beam sputtering to provide a conducting surface for STM and FESEM imaging. These coatings have been shown to introduce minimal topography to the original sample surface.
Impurity-controlled contrast in secondary-electron images of reaction-bonded silicon carbide
Authors: Youngman R.A. 
Published: June 2020

Reaction-bonded SiC is formed by the high temperature (>2100°C) heat treatment of a mixture of alpha-SiC powder and organic binders in the presence of elemental Si. The bonding occurs by the in-situ formation of beta-SiC from the reaction of the pyrolyzed binder and the Si. Substantial microstructural characterization of these materials has been carried out in the past. A particular feature of these analyses is the so-called trace-impurity-controlled contrast of secondary electron (SE) images of uncoated specimens. This report describes further attempts to elucidate the origin of this contrast mechanism.Samples of reaction-bonded SiC (Hexoloy KT, The Carborundum Co.) were prepared for multiple-technique analysis. This was accomplished by preparing an optical thin section for reflected and transmitted optical microscopy. Regions of interest were diamond-scribed on the optical microscope (Leitz, Orthoplan) and then SE and backscattered electron (BE) microscopy (CamScan, Series IV) of the same areas (both coated and uncoated with evaporated carbon) was conducted. Finally, the same areas were imaged in a secondary ion mass spectrometer (SIMS) (Cameca, IMS3F) to detect trace and major impurity levels.
Effect of refractory elements on microstructure and fracture of rapidly solidified nickel base alloys
Authors: Adeva P. , González-Carrasco J.L. , Ibáñez J. , Aballe M. 
Published: June 2020

In order to evaluate the effect of refractory elements on the microstructure and properties, and especially on ductility of nickel- base rapidly solidified materials, three rapidly solidified alloys have been obtained by melt spinning under helium atmosphere of 0.04 Pa at linear speed of 47 ms-1 in the form of smooth 20 ∼30 ∼m thick and ∼1 mm wide ribbons. Starting materials were inert gas induction melted alloys with 12 at.% Cr and 20 at.% A1, with additions of 1.5 at.% Nb, 1.5 at.% Ta or 1.9 at.% Mo respectively, balance nickel. Samples were observed by AEM and EPMA in the as-cast condition, and by SEM-EPMA after mechanical testing at temperatures between 300 and 773K. Tensile specimens were suitable ribbon lengths with gauge length 16 mm, and initial strain rate was 10-4s-1. Results were compared with those previously obtained on a similar alloy not containing refractory elements (Ni - 15 at.% Cr - 20 at.% Al).Longitudinal sections show columnar through thickness grains (Fig.l) and in some cases equiaxed grains in the region close to the gas side. The free surface shows grains and cells with an average area in the prepared section of ∼3 μm2 and 0.8 μm2 approximately, as measured by quantitative metallography.
Microstructure of mechanically alloyed and hot-pressed Al5CuZr2
Authors: Mitchell T. E. , Desch P. B. , Schwarz R. B. 
Published: June 2020

Al3Zr has the highest melting temperature (1580°C) among the tri-aluminide intermetal1ics. When prepared by casting, Al3Zr forms in the tetragonal DO23 structure but by rapid quenching or by mechanical alloying (MA) it can also be prepared in the metastable cubic L12 structure. The L12 structure can be stabilized to at least 1300°C by the addition of copper and other elements. We report a TEM study of the microstructure of bulk Al5CuZr2 prepared by hot pressing mechanically alloyed powder.MA was performed in a Spex 800 mixer using a hardened steel container and balls and adding hexane as a surfactant. Between 1.4 and 2.4 wt.% of the hexane decomposed during MA and was incorporated into the alloy. The mechanically alloyed powders were degassed in vacuum at 900°C. They were compacted in a ram press at 900°C into fully dense samples having Vickers hardness of 1025. TEM specimens were prepared by mechanical grinding followed by ion milling at 120 K. TEM was performed on a Philips CM30 at 300kV.
An Electron Microscope study of structure of high damping capacity Ti - 644 casting titanium alloy during the quenching and aging
Authors: Guozhao Xu , Jianke Sun , Yuli Fan , Guilan Cheng 
Published: June 2020

Ti-6A1-4V-4Mo casting titanium alloy is a new high damping capacity α + β martensitic titanium alloy, which suits for the manufacture of rotating blades particularly of large sizes or for highspeed operations. It was found that a remarkable improvement in damping capacity is made possible by rapidly cooling the alloy from a proper temperature in the α + β phase temperature range after heating a predetermined time. Especially the alloy will have the highest damping capacity when heating in the 850-900°C temperature range.Fig. 1 Shows the relation between the damping capacity of the alloy and solution treatment temperatures. It also was found that damping capacity of the alloy decreases when the specimens were reheated at, 150-300 ° C temperature range for a certain time after solution treatment, the results show in Fig. 2.