bluuebunny/crossref_metadata_2025_split huggingface dataset:
CBED analysis of extended defects in melt-grown GaSe single crystals
Authors: De Blasi C. , Manno D. 
Published: June 2020

The study of dislocations and stacking faults in melt grown GaSe single crystals has been carried out by the Convergent Beam Electron Diffraction (CBED) technique.The presence of stacking faults induces distortions in the Kikuchi lines observed in the CBED transmitted disk. According to the kinematical condition of the stacking fault visibility, such lines show modifications when g·R is not integer, The displacement vector R has been determined by the analysis of the visibility and invisibility conditions in the transmitted disk, recorded according to the Tanaka method, The Burgers vector b of dislocations has been determined by the analysis of the modifications induced both in Kikuchi lines and in the First Order Laue Zone (FOLZ) reflections, observed in low camera length CBED patterns. Splitting and unsplitting of the reflections correspond to the visibility and invisibility of the dislocations in the kinematical approximation of diffraction contrast, The condition g·b = 0 is not strictly a sufficient condition for the vanishing of the modifications induced by the dislocation, neverthless it is generally very useful as a criterion for determining the direction of b, Moreover, some reflections g give g·b = ⅓ in the case of partial dislocations. This condition does not produce enough contrast to be detected, so that it is one more for the defect invisibility. The Thompson construction has been used in order to calculate the amplitude of b and to discriminate perfect or partial dislocations.
In situ straining experiments in the Transmission Electron Microscope
Authors: Messerschmidt Ulrich 
Published: June 2020

Recently a number of in situ straining experiments have been carried out at temperatures between about 80 K and 1200 K. A new HVEM straining stage was constructed for temperatures above 1300 K. Its design features are: top entry double tilting stage, thermal expansion drive of high stiffness, heating by electron bombardment, and water cooling to quickly reach a steady state.The following deformation phenomena have successfully been treated by in situ experiments:Determination of the effective stress from the curvature of bowed-out dislocation segments: As shown by in situ experiments on MgO crystals, the line tension of dislocations may differ from its theoretical value. Nevertheless, the anomalous temperature dependence of the effective stress in ordered alloys as well as for prismatic slip in Be has been determined in accordance with macroscopic experiments. Measurement of velocities and kinematic behaviour of dislocations: In situ experiments allow the coordination of the motion of individual dislocation segments with their geometrical configuration.
TEM study of buried yttrium silicide formed by ion implantation
Authors: Alford T.L. , Theodore N.D. , Barbour J.C. , Carter C.B. , Mayer J.W. 
Published: June 2020

Metal silicides are now used extensively in very-large-scale-integrated (VLSI) electronics due to their low resistivity, good thermal stability, and ability to form on Si. Of these silicides, yttrium silicide, YSi2-x has essentially 0% lattice mismatch with (111)Si, a low Schottky barrier height on n-type Si, and a unit cell based on the AlB2-type structure, but with 15-20% vacancies on the Si sublattice. Recent investigations of high-temperature ion implantation of yttrium ions into Si have emphasized the formation of buried-silicide layers. This study is focussed on the microstructure and defects in the vicinity of buried YSi2-x layers formed by Y-ion implantation into Si.Yttrium-silicide buried layers were formed by implanting 330 or 660 keV Y ions into (11l)Si substrates held at 450°C followed by a 1000°C, 1-hour vacuum anneal. The implant fluences varied from 1 to 3.6×l017 Y/cm2. Cross-section transmission electron microscopy (XTEM) analysis was carried out using a JEOL 4000EX electron microscope operating at 400 kV.
Characterization of defects in Si films on SiO2 layer
Authors: Liu Ansheng , Shao Beiling , Yuan Jianming 
Published: June 2020

SOI (Silicon-on-lnsulator) offers many advantages for integrated circuits including faster switching speed, high packing density, radiation resistance, and latch-up free. It can also be used in the integration of high voltage devices and/ or sensors. Defect-free Si films with a small interior stress are required for the application mentioned above. Therefore a heat-sink and a valley entrainment structure (Fig. 1) were made in order to confine defects to predetermined locations and to leave the other areas of the recrystallized silicon film defect-free.Using a cross—section specimen electron microscopy we have observed some kinds of defects in unseeded rapid zone-melting-recrystallized (RZMR) Si films which were prepared with a RF-induced graphite strip heater system. The scanning speed of the graphite strip heater is 11 mm / sec. Fig.2 shows a cross-section image of a valley structure specimen. Not any defect has been found in region A, which means that about 10μm wide defect-free Si film can be obtained by the process. Region C is an unpatterned normal area with a uniform thickness.The subgrain boundaries (SGBs) with an interval less than 6μm were observed in the region C.
Electron microscope study of differential ion implantation damage in AlAs/GaAs epitaxial layers
Authors: Cullis A G , Jacobson D C , Poate J M , Smith P W 
Published: June 2020

Ion implantation processing applied to superlattice structures can produce controlled intermixing of the different strata and a range of studies have focused with special interest upon the GaAs-GaAlAs and InP-InGaAs systems. However, there can be marked differences in the susceptibilities of the superlattice materials to ion damage build-up which, thus, complicates interpretation. The present work has applied transmission electron microscopy (TEM) to the study of differential ion damage in the GaAs-AlAs system, together with an examination of thermal annealing behaviour.Single ˜90nm heteroepitaxial layers of AlAs were produced within a GaAs matrix grown by molecular beam epitaxy upon (001) GaAs substrates. Ion damage was introduced (77K) using Si+ ions with overlaid doses of 3.5×l014 ions/cm2 at 150keV and 7×1014 ions/cm2 at 200keV. Some samples were then subjected to rapid thermal annealing for 10s at 600°C or 800°C. The structure of the material after the various treatments was studied in cross-sectional samples by both conventional and high resolution TEM using a JEM 4000EX instrument operated at 400kV.
Silicon-induced disordering in GaAs-AlAs superlattices
Authors: Baba-Ali N. , Harrison I. , Tuck B. , Ho H.P. 
Published: June 2020

Compositional disordering of quantum well structures by impurity diffusion has attracted increasing interest since it was first discovered by Laidig et al in 1981. This phenomenon not only provides a simple way of fabricating new integrated optical devices but also enables fundamental studies of impurity diffusion and self-diffusion. Silicon has been found to induce intermixing in AlGaAs based multiquantum wells. Various techniques have been used to incorporate Si, these are diffusion from the surface, implantation followed by annealing and diffusion from a grown-in source.In the present work, diffusion in Molecular Beam Epitaxy (MBE) grown samples has been carried out from a grown-in source. The TEM characterization of the as-received specimen has revealed that the structure consisted in a 0.4 um thick Si-doped Al0.33Ga0.66As layer which was sandwiched between two superlattice areas each of which consisted of 17 periods of alternating GaAs(400A)-AlAs(200A) layers (Figure 1) .The samples were annealed in sealed Silica ampoules under various Arsenic pressures at 815°C and 915°C. Secondary Ion Mass Spectroscopy (Figures 4 and 5) demonstrates that the change in the Ga and Al profiles is the consequence of Si diffusion through the Superlattice layers. The TEM investigation of the samples (Figures 2 and 3) confirmed that intermixing had been induced during the diffusion. It also revealed the formation of intrinsic dislocation loops in the annealed specimens. The contrast analysis of the loops indicates that these are of the interstitial type. Finally,increasing the Arsenic overpressure has been found to cause preferential diffusion of Si towards the surface (Figures 6,7 and 8).
Amorphous structure of semiconducting CdAs2 doped with Ge
Authors: Hong K.S. , Berta Y. , Speyer R.F. 
Published: June 2020

In crystalline CdAs2, Cd and As atoms are arranged spirally, to form comparatively large (A- site) and small (B-site) vacant sites, bordered by As atoms. This crystalline structure is shown in Fig. 1. The structure of amorphous CdAs2 has been taken to closely resemble that of the crystalline form; doping the compound with Ge atoms would initially cause Ge occupation of the large A-sites with minimal local lattice distortion. Larger amounts of the dopant, in excess of the solubility limit, would cause the rejection of Ge atoms from the lattice, since occupation of the comparatively smaller B-site occupation would otherwise cause severe lattice distortion. With germanium additions in excess of CdGe0.6As2, the amorphous CdAs2 structure transforms to the CdGeAs2 structure, wherin the cation-sites are equally occupied by Cd and Ge at alternate sites.Samples with appropriate compositions were fabricated by water-quenching the molten compound,vacuum sealed in carbon coated (by pyrolysis) fused silica tubes. The samples were mechanically thinned and ion-milled using a liquid nitrogen cold stage, for examination in the TEM and for EDS.
Microstructural evaluation of reactive ion etched - regrown GaAs
Authors: Cole M.W. , Dutta M. , Rossabi J. , Lehman J.L. 
Published: June 2020

Reactive ion etching (RIE) is a preferred dry process step for fabrication of submicron III-V semiconductor device structures. This kinetically assisted chemical dry etch process offers several important advantages over other etching methods, namely etch anisotropy, etch rate control, selectively, accuracy, uniformity across the wafer and reproducibility. As a result of these desirable characteristics, a number of semiconductor device designs involve REE in their device fabrication process. Some of the more novel designs involve lateral quantum well arrays, whereby fabrication requires molecular beam epitaxial (MBE) regrowth on RIE semiconductors.A major drawback of RIE is the potential lattice damage introduced by energetic ion bombardment and contamination. This material damage may lead to deterioration of device performance. It is important to identify and understand this RIE induced damage in order to develop and refine the RIE process, i.e. minimize crystal damage and thus optimize device performance. This study identifies and analyzes the damage associated with various RIE parameters used for quantum well fabrication. Microstructural characterization via TEM is used to identify the nature of lattice defects, their distribution, and density. Optical methods, Photoluminescence and Raman spectroscopy are used to evaluate the crystal damage and serve as a reliable comparators for the TEM results.
Observation of magnetic domain in magnetic disk
Authors: Nagata F. , Shimotsu T. , Tsuruta C. , Kubozoe M. 
Published: June 2020

A technological key to successful development of high-density magnetic disk lies in how to prevent mutual interference between adjacent bits i.e. how to provide narrower and simpler configulation of magnetic domain. Development of observation technique of finer magnetic domain, therefore, has been strongly required. Lorentz microscopy is one of the most promising method. Some studies have been made to observe recorded magnetic thin films.The purpose of the present investigation is to develop high resolution Lorentz microscopy(out of focus method) for investigation of recorded magnetic disk.High resolution and high voltage electron microscope (H-9000UHR) is used operating at 300kV. Objective lens is excited to realize smaller aberration. In order to protect specimens from magnetic field of objective lens, a special specimen holder is developed. Figure 1 shows a sectional view of objective lens and specimen holder.
The effect of sputtering pressure on microstructure and recording performance of high-density magnetic recording media
Authors: Nguyen Thao A. , Yogi Tadashi , Lambert Steven E. 
Published: June 2020

Understanding the magnetic properties of thin films applicable to high density recording requires detailed knowledge of the microstructure and microchemistry of the film. Interactions such as exchange and magnetostatic as well as anisotropies have been shown theoretically to influence the magnetic properties and recording characteristics of the media. These magnetic interactions and anisotropies are very sensitive to microstructure. This study reports the efTcct of sputtering pressure on the microstructurc and magnetic properties of thin CoPtCr films. The relation between the microstructural features and the magnetic interactions will be discussed.The film structure, C/Co77Pt6Cr17/Cr, was sequentially sputtered onto Si and NiP/AlMg substrates precleaned by an rf plasma. The thicknesses were 25/25-60/100 nm respectively. Sputtering pressures ranging from 3 to 24 mtorr were investigated. The magnetic properties of the films (coercive field, Hc, coercive squareness, S*, remanent and saturation moments, Mrand Ms) were determined by vibrating sample magnetometry. The magnetic recording measurements were made with thin film inductive write heads and experimental shielded magnetoresistive read head with a track width of about 10μm. The head-media spacing was 5 μin. Noise voltages for transition densities up to 3000 fc/mm were determined in the usual fashion. The microstructures were studied using the JEOL JEM 2000 FX and 4000 EX transmission electron microscopes.
Effects of electron irradiation on alkaline earth fluorides
Authors: Diehl P. , McCartney M.R. , Smith David J. 
Published: June 2020

Alkaline earth fluorides are important materials in the electronics industry because of their use in the epitaxial growth of semiconductor-on-insulator (SOI) devices. Their main advantages are their close lattice match with the common semiconductors, and the fact that they evaporate as molecular units upon heating which implies good control of film stoichiometry in Molecular Beam Epitaxy. More recently, further interest has developed relating to their use in nanolithography because they are materials which can be suitably patterned with an electron beam in device processing.Moreover, some inorganic fluorides potentially offer inherently higher resolution than resists so far used.Various studies have been made on the effects of irradiation on these Group IIA fluorides. It has also been noted during electron microscope characterization of the SOI structures that these fluorides are very easily damaged. Since image detail is lost, it has been suggested that the fluorides are becoming amorphous.
HREM studies of structure, defects and phase transformation in zirconia and Mn stabilised zirconia
Authors: Sharma Renu 
Published: June 2020

Zirconia is known to exist in three different structure types: monoclinic, tetragonal and cubic. Monoclinic is the room temperature form that transforms to tetragonal and finally to cubic at progressively higher temperatures. The monoclinic to tetragonal transformation is reversible, exhibits hysteresis and has been widely studied by thermal analysis, high temperature x-ray diffraction and electron diffraction. This transformation has an undesirable effect on some materials properties. The cubic form of zirconia has been stabilised with yttria, calcia, alumina and magnesia. The decomposition of zirconium carbonate and zirconium manganese carbonate to the respective oxides and their phase tranformation has been studied in situ by electron diffraction and high resolution electron microscopy (HREM) and the results are reported here.The carbonates used in these studies were precipitated from their aqueous solution. Thin crystal fragment were dispersed on holey carbon grids using a suspension in ethanol. A JE0L 4000EX microscope, with double tilt goniometer and on-line Digital MicroVAX II image-analysis system, operating at 400KV, was used for HREM studies.
High-resolution work on zeolites
Authors: Alfredsson V. 
Published: June 2020

Zeolites are aluminosilicates with very open frameworks . The structures are characterized by the presence of tunnels or large cavities. The Si and Al sit in the centre of oxygen tetrahedra which are linked together.HREM work on zeolites has two big disadvantages. The greatest problem is the beam sensitivity of the crystals. After a short time in the electron beam they become amorphous. To improve the stability, the zeolites are made with as high Si/Al ratio as possible, the microscope is run with a very spread electron beam and at low magnification. A TV-camera with an image intensifier is used for focusing. Higher accelerating voltage has also proved to enhance the lifetime of the crystals in the beam. Secondly, an artefact caused by the shape of the contrast transfer function (CTF), gives false information to the images creating dark contrast in areas where there are no atoms. Two different solutions to this problem have been worked out. The first is to change the shape of the CTF by changing the focus and the second by removing the artifact effect caused by the CTF by means of image processing.
Radiation damage in rutile and perovskite
Authors: Buck E.C. , Jones I.P. 
Published: June 2020

The radiation damage characteristics of some of the phases of SYNROC, notably rutile and the perovskites, barium titanate and calcium titanate have been investigated. The effects of electron irradiation on a number of simple oxides, such Al2O3 , ZnO and MgO are well documented. The effects are generally more complicated than those in metals, as there are two or more charged species usually of significantly differing masses. Electron irradiated oxides generally form pure edge interstitial loops and undergo a decrease in displacement energy (Ed ) with increasing temperature. The latter effect has been ascribed to the occurrence of two separate displacements, one for the anion and one for the cation, corresponding to the minimum and maximum in the temperature versus displacement voltage curves. Optical measurements have been used to distinguish anion from cation displacements.Irradiation of rutile in the temperature range 200°C to 400°C with lMeV electrons caused the production of pure edge interstitial unfaulted dislocation loops of the type b=a<100> lying on {100}s planes (FIG. 1.).
Successive observation of hydration growth with cryo-SEM
Authors: Suzuki T. , Ogura K. , Ono A. 
Published: June 2020

A cryo-scanning microscope enables us to observe specimens at a temperature as low as 140K. Thus a specimen containing much water can be observed in a frozen state, and morphological changes of specimens such as hydrates can be stopped, for observation at an adequate stage of reaction. The former feature is mainly used for biological specimens. We made an experiment to confirm the possibility of the good use of the latter feature for observation of the hydration process.When water is added to cement or plaster, the hydrate is grown and its morphology is extremely changed after the reaction. The morphology of the materials before or after the reaction can be observed with a conventional SEM easily. But, morphological changes under reaction cannot be observed by the conventional method. Such an observation, especially successive observation of the same region, is considered to be quite interesting and important.
TEM observation of iron oxide pillars in montmorillonite
Authors: Mori H. , Murata Y. , Yoneyama H. , Fujita H. 
Published: June 2020

Recently, a new sort of nano-composites has been prepared by incorporating such fine particles as metal oxide microcrystallites and organic polymers into the interlayer space of montmorillonite. Owing to their extremely large specific surface area, the nano-composites are finding wide application[1∼3]. However, the topographic features of the microstructures have not been elucidated as yet In the present work, the microstructures of iron oxide-pillared montmorillonite have been investigated by high-resolution transmission electron microscopy.Iron oxide-pillared montmorillonite was prepared through the procedure essentially the same as that reported by Yamanaka et al. Firstly, 0.125 M aqueous solution of trinuclear acetato-hydroxo iron(III) nitrate, [Fe3(OCOCH3)7 OH.2H2O]NO3, was prepared and then the solution was mixed with an aqueous suspension of 1 wt% clay by continuously stirring at 308 K. The final volume ratio of the latter aqueous solution to the former was 0.4. The clay used was sodium montmorillonite (Kunimine Industrial Co.), having a cation exchange capacity of 100 mequiv/100g. The montmorillonite in the mixed suspension was then centrifuged, followed by washing with deionized water. The washed samples were spread on glass plates, air dried, and then annealed at 673 K for 72 ks in air. The resultant film products were approximately 20 μm in thickness and brown in color.
Austenite transformation products in quenched low-carbon HSLA steel
Authors: Varughese R. , Howell P. R. 
Published: June 2020

The alloy design for the HSLA-100 plate steel aims at optimizing the strength and toughness through developing a refined ferritic microstructure while enhancing the weldability by lowering the carbon levels to 0.04 wt% or less. The austenite grain refining potential of microalloying additions of niobium is coupled with the hardenability effects of Mn, Ni, Cr and Mo to achieve a fine acicular microstructure through water quenching prior to age-hardening through copper precipitation. Wilson et. al, in developing CCT diagrams for these HSLA steels noted that the as-quenched microstructure in the 0.04 wt% carbon steel consisted of a mixture of martensite and bainite and their results indicated that a fully martensitic microstructure at slightly higher carbon levels contributed to enhanced toughness. In this paper, we present our results on the microstructural features found in an oil-quenched sample of the HSLA-100 steel.The chemical composition (in weight percentage) of the 1 1/4" thick plate steel is given below.
TEM of the tempering reactions in 2.25 Cr 1Mo steel
Authors: Parameswaran P. , Vijayalakshmi M. , Raghunathan V.S. 
Published: June 2020

The precipitation of carbides in the ferritic steels, has been the subject of several investigations. This paper discusses the precipitation of carbides in 2.25Cr-1Mo steels. The sequence of changes that occur in the morphology, structure and composition of carbides as a function of tempering temperatures and carbon content, 0.06%C(A) and 0.11%C(B) has been examined in detail.The steels were austenitized at 1323K for 1h and quenched in flowing argon gas(AQ), followed by tempering in the range 823-1023K for varying durations of time. Structural and chemical information of carbides were obtained using electron diffraction and analytical microscopy respectively. The Cliff-Lorimer ratio method, incorporating theoretically calculated correction factors was employed in the analysis of spectra.Following AQ, both steels exhibited a mixture of bainite and polygonal ferrite. Fig.1 shows the presence of coarse distribution of carbides in bainite and relatively carbide-free ferrite matrix in steel B. The repartitioning of carbon takes place during AQ and transforms carbon rich regions into bainite. The inset in Fig.1 is the SAD pattern obtained from the bainite, the analysis of which confirms that the precipitates are Fe3C.