bluuebunny/crossref_metadata_2025_split huggingface dataset:
Weak beam image of a superlattice dislocation in deformed Ni3 (AlHfB)
Authors: Wu X. F. 
Published: June 2020

A number of intermetallic compounds with the L12 structure exhibit a strange increase in the flow stress and work-hardening rate with increasing temperature. Despite the success of some model in explaining macroscopic properties, the detailed dislocation processes of model that are assumed to take place have not been observed in microscope. This work is an attempt to determine how the dislocation fine structure is related to the deformation behaviour of L12.Single crystal Ni-23Al-1Hf-0.1B(at%) was used in the present study. direction was chosen as compression axis. Samples were deformed to plastic strain of 6%, specimens were cut parallel to by spark erosion. Fined electropolishing was donein solution of 1% perchloric acid in methanol at −50°c and 30V. The g/3g diffraction condition used in weak beam observation.Fig1 shows the dislocation structure in foil. Long fairly straight screw dislocations with b=a[011] are imaged. The formation of dipoles is regarded as a characteristic and unusual feature of the dislocation structure. This indicates that annihilation is difficult at room temperature deformation. Weak beam images of superlattice dislocations are shown in fig.2 by using different reflections. The dislocation CC is long straight screw dislocation.
HRTEM observations of layer structure and stacking faults in MoS2 crystals
Authors: Shiojiri Makoto , Takahashi Noboru , Enomoto Susumu 
Published: June 2020

MoS2 has a six-folded coordinated layer structure represented by the stacking symbol aβ ab ab The Greek letters refer to Mo atoms in the positions (2c) ± (⅓ ⅔ ¼) , and the italic letters refer to S atoms in the positions (4f) ± (⅓ ⅔ 0.629; ⅔ ⅓ 0.129) of the space group C6/mmc. The bonds between two S layers are mainly Van der Waals type and hence considerably weaker than the covalent bonds between Mo and S atoms.A cleaved flake of MoS2 was embedded in synthetic resin and ultramicrotomed with a diamond knife perpendicular to the cleaved surface. The section was observed with an ABT EM-002B electron microscope having a UHR lens of Cs=0.4 mm.Fig. 1 shows an observed HRTEM image of an MoS2 crystal and its electron diffraction pattern. The incident beam was parallel to the [2
0] axis.
The use of HREM in studying clay minerals
Authors: Qing Chen Quan , Lu Xing 
Published: June 2020

A wider scope of clay research has been opened by investigators in various branches of science and technology due to their increasing interest in such materials. Electron microscope is one of the important methods for studying clay and clay minerals. Although a previous contribution of electron microscopy was to clarify the morphology and later electron diffraction (ED) of fine clay particles.However with the continous improvement of instrument and high resolution electron microscopy (HREM) techniques has provided more detailed information of clay minerals. This paper presents the use of HREM in stúdying clay minerals among our research.1. Analysis of the structure of clay minerals
Recent advances in crystal structure analysis have indicated that disordered features are commonly revealed to various extents in clay mineral structure, such as polytypes,stacking disorders,mixed-layers.......etc. When the fraction of disordered feature is rather low, which cannot be distinguished by other method such as x-ray diffraction,however by using HREM lattice imaging, ED, and computer simulating (CS), which can be distinguished distinctly and sensitively. Fig.1a shows the structure of kaolinite with enantio morphic types i.e. left-handed and right-handed kaolinite. The computer simulated image (CSI) and electron diffraction pattern (EDP) are included for interpretation. It was also found that dickite is exhibited as intergrowth or stacking faults in the koalinite.
A multislice calculation of asymmetry of the weak-beam images of intrinsic stacking faults
Authors: Liu Z. Q. , Cockayne D. J. H. 
Published: June 2020

Weak-beam images of stacking faults with one sign of a reflection can show some contrast changes to the images with the opposite sign of the reflection, that is so called asymmetry. This was first reported by Cullis and Booker, then this research has been carried on. For example. Foil et al and Cockayne et al.The asymmetry for intrinsic stacking faults seems more complicated experimentally and theoretically. This asymmetry was observed (e.g.,Liu), and an example is shown in Fig. 1, where intrinsic stacking fault A shows less contrast with 400 in (a) than with 00 in (b). A multislice calculation was carried for an intrinsic stacking fault inclined on 001 silicon foil. The unit cell has 001 axis down along the incident beam, and is shown in Figure 2. Figure 3 shows the projected potential arrays of several successive slices with the thickness of 2.71 Å. Line A A' separates the arrays into two parts with different projected potentials due to the existence of the fault. The darkened dots which actually have larger values of the potential correspond to the atomic positions in the slices. The shifts of the atoms near the fault can be seen. The calculation were carried for the foil thickness of 271.00 - 371.07Å with relatively large deviation parameter s (.054Å)-1 The Laue center has been carefully chosen so that the weak-beam conditions are obtained. Five successive supercells with the same thickness but with different depths of the fault were used so that the fault is joined up smoothly tor the calculation. The final results of the calculation is shown in Figure 4, where (a) is for 040 and (b) is for 040. Five different symbols represent five different depths of the fault. The periodicity of the fault agrees with 1/s. The contrast ratio for±040 is 0.85.
Interface motion during recrystallization of amorphous NiSi2
Authors: Batstone J. L. , Smith D.A. 
Published: June 2020

Recrystallization of amorphous NiSi2 involves nucleation and growth processes which can be studied dynamically in the electron microscope. Previous studies have shown thatCoSi2 recrystallises by nucleating spherical caps which then grow with a constant radial velocity. Coalescence results in the formation of hyperbolic grain boundaries. Nucleation of the isostructural NiSi2 results in small, approximately round grains with very rough amorphous/crystal interfaces. In this paper we show that the morphology of the rccrystallizcd film is dramatically affected by variations in the stoichiometry of the amorphous film.Thin films of NiSi2 were prepared by c-bcam deposition of Ni and Si onto Si3N4, windows supported by Si substrates at room temperature. The base pressure prior to deposition was 6 × 107 torr. In order to investigate the effect of stoichiomctry on the recrystallization process, the Ni/Si ratio was varied in the range NiSi1.8-2.4. The composition of the amorphous films was determined by Rutherford Backscattering.
In situ investigations of the fcc to hcp martensitic phase transformation in CoNi
Authors: Karnthaler H.P. , Waitz T. 
Published: June 2020

CoNi alloys show like pure Co a martensitic phase transformation between the fcc high temperature phase and the hcp low temperature phase. In Co+32%Ni the mean transformation temperature is at room temperature RT. Since the hysteresis is rather large (± 150°C) both phases can be observed in a stable configuration at RT. The two close packed lattices can transform into each other by the movement of a Shockley partial dislocation on every other close packed plane. In the case of the fcc → hcp transition there are four {111} planes which can act as habit planes. Therefore, caused by topological reasons the growing lamellas will hinder each other during their expansion. This seems to be an important difference to the reversed transformation where only one habit plane exists.Single crystals of Co+32%Ni were grown under vacuum by a modified Bridgeman technique. The crystals were in the fcc phase at RT. Discs of 1mm diameter with 〈112〉 orientation were prepared by spark erosion.
Precipitation in silicon-implanted by oxygen and carbon plus oxygen
Authors: Chen Y. L. , Carpenter R. W. , Sjoreen T. P. 
Published: June 2020

Interest in precipitation processes in silicon appears to be centered on oxygen and carbon impurities in thermally aged materials, and on oxygen implanted materials to form buried dielectric layers. The precipitation reaction products are small, and the presence of carbon is often an important consideration. This abstract reports high resolution electron microscopy observations of precipitate morphology in FZ-Si implanted with oxygen (2.3×l020cm-3 concentration at projected range. Rp). and with oxygen plus carbon (both 1.2×l020cm-3concentration at Rp), and then post-implanted annealed at 923K for 120 hours. These oxygen and carbon concentrations are significantly higher than the saturation oxygen and carbon concentrations in Si at the melting point, which are ∼2×l018 cm-3.After mechanical and argon-ion-milling thinning, (001) wafers were examined in [011] cross-section with an LSI 002B at 200kv for HREM and a Philips EM400ST FEG at l00kv for EELS. A typical implanted region is shown in Fig. 1a for O-implanted and Fig. 1b for O-plus-C-implanted specimens.
Copper precipitation on extrinsic defects in silicon
Authors: Rice P.M. , Kim M.J. , Carpenter R.W. 
Published: June 2020

The gettering of impurity copper in silicon has been investigated for over a decade because of its technological importance in electronic device fabrication.it is known that Cu can be extrinsically gettered in silicon at deliberately introduced nucleation sites. However, its reaction mechanism and the nature of the reaction product are not well understood. Here we report the interaction of Cu with dislocations in Si created by mechanical abrasion.A damaged region was introduced into CZ{001} silicon wafers on one side by abrasion. A Cu layer 200nm thick was deposited onto the abraded surface in a UHV chamber at room temperature. After Cu deposition the wafers were sealed immediately into quartz ampules under vacuum and annealed at 1000 C for 24 hrs, followed by quenching. Cross section specimens were prepared by mechanical dimpling and Ar beam ion milling. Diffraction contrast imaging and microdiffraction experiments were done in a JEM-2000FX at 200kV, and a Philips 400TEM/STEM/FEG at 100kV.
Phase separation and silicide formation in the films of Pd-W alloys on Si
Authors: Rozhanski N. , Lifshitz V. 
Published: June 2020

Pd-W alloy films are of interest because of their use for contact fabrication in microelectronic devices.In the present work Pd2 5W7 5, Pd4 0W6 0, Pd9 0W1 0 films were sputter deposited on Si(100) and only Pd9 0W1 0 films were polycrystalline.The amorphization of Pd- W films, possibly due to impurities, was not observed previously. The reaction of Pd9 0W1 0 films with a Si substrate begins at 200°C and leads to the formation of Pd2Si in two equivalent epitaxial orientations: A and B.In contrast to Ni-Nb films the presence of the native SiO2 layer under Pd-W alloy does not prevent the diffusion processes and the formation of silicides both on bulk and on plan-view specimens.Amorphous Pd-W films do not react with Si up to∼500°C and their crystallisation begins at T∼575°C.The reaction is also followed by the formation of two types of epitaxially oriented Pd2 Si islands as shown in Figure 1.The crystallisation of the films is accompanied by the formation of W grains.Pd crystals were not observed, that is possibly due to Pd precipitation at W grain boundaries.
The reaction of amorphous Ni-Nb films with Si in the presence of a native SiO2 layer
Authors: Rozhanski N. , Barg A. 
Published: June 2020

Amorphous Ni-Nb alloys are of potential interest as diffusion barriers for high temperature metallization for VLSI. In the present work amorphous Ni-Nb films were sputter deposited on Si(100) and their interaction with a substrate was studied in the temperature range (200-700)°C. The crystallization of films was observed on the plan-view specimens heated in-situ in Philips-400ST microscope. Cross-sectional objects were prepared to study the structure of interfaces.The crystallization temperature of Ni5 0 Ni5 0 and Ni8 0 Nb2 0 films was found to be equal to 675°C and 525°C correspondingly. The crystallization of Ni5 0 Ni5 0 films is followed by the formation of Ni6Nb7 and Ni3Nb nucleus. Ni8 0Nb2 0 films crystallise with the formation of Ni and Ni3Nb crystals. No interaction of both films with Si substrate was observed on plan-view specimens up to 700°C, that is due to the barrier action of the native SiO2 layer.
Investigation of the uniformity of well thickness in InP/InGaAs single quantum wells by large-angle convergent beam electron diffraction and dark-field imaging
Authors: Jordan IK , Cherns D. , Hockly M , Spurdens PC 
Published: June 2020

The sharpness of interface, and the uniformity of well width, is of great interest in the growth of single quantum well (SQW) structures. These properties are usually investigated using High resolution electron microscopy (HREM) on cross sectioned samples. However this technique allows the imaging of only very small areas, and long Tange structure present in a sample may not be detected.In the lattice matched InP/InGaAs system discussed here selective etches enable the preparation of plan view samples with up to 1mm2 of flat, electron transparent, area. Large angle convergent beam electron diffraction (LACBED) may then be used on these samples to obtain an extended rocking curve. Analysis of the rocking curve enables a measurement of the mean well width to be made. All structures reported on here were grown using MOVPE.At large values of deviation parameter, s, typically greater than 0.003Å−1, the main features of rocking curves can be interpreted using the kinematic approximation.
The oval defects on MBE grown GaAs(100)
Authors: Hsu Tung , Petrich G.S. , Cohen P. I. 
Published: June 2020

Oval defects were observed on specimens of MBE grown GaAs(100) samples. Substrates were GaAs(100) tilted 2ò toward [011] (A misorientation); chemically etched before growing 0.2μm of GaAs at 600òC, at a rate of 0.4μm/h, and using a 3:1 As:Ga flux ratio. After the growth samples were transferred through air to a JEOL-200CX electron microscope for REM and RHEED study,Surfaces of the sample exhibited bunched atomic steps and wide atomically flat (100) terraces. There were approximately 100 such defects, large and small, within a specimen surface of 1 mm2.The defects were of various sizes, indicating that they were at different stages of growth, but had the same general shape. After shooting a series of pictures from different azimuth angles, a three demensional computer model is then constructed and the model is tilted and rotated to simulated the views from different directions. There is a good agreement between the simulated and the experimental pictures.
The characterization of Ga0.5In0.5P/GaAs solar cells grown on Si substrates
Authors: Jones K.M. , Al-Jassim M.M. , Olson J.M. , Kurtz S.R. , Kibbler A.E. , Vernon S.M. 
Published: June 2020

Multijunction solar cells have the potential of achieving conversion efficiencies in excess of 30%. It has been recently demonstrated that Ga0.5In0.5P/GaAs tandem solar cells can achieve efficiencies higher than 27%, These devices are grown on GaAs substrates. However, there is an increasing need for a cheaper, lighter substrate with higher thermal conductivity than GaAs for space solar cell applications. In this work, we have investigated the structural and luminescent properties of GaAs/GaInP multilayers grown on Si substrates. All layers were grown by MOCVD on (100), n-type Si substrates misoriented by 2° towards (110). The TEM examination was performed in a Philips CM-30 TEM operating at 300 KeV.The first part of this study focussed on the growth of GaAs on Si for further use as a substrate for growing GaAs/GaInP cell structures. GaAs layers grown under standard MOCVD conditions exhibited dislocation densities in the 2-4 x 108 cm−2 range for 2μm thick layers. On the other hand, thermal cycle growth (TCG) gave rise to layers with significantly improved structural quality. This was carried out by several repetitions of deposition-annealing-cool down cycles during the growth. The effect of annealing on dislocation propagation is quite evident in TEM cross-sections (Fig. 1). The majority of defects are confined to a relatively thin region close to the interface. Wafers that had been in situ annealed 3 or 4 times exhibited a heavily faulted interface region, approximately 5000 Å thick, with the rest of the GaAs layer having a dislocation density in the 7-9 x 106 cm−2 range.
Spin-polarized Scanning Electron Microscopy
Authors: Koike Kazuyuki , Matsuyama Hideo 
Published: June 2020

Spin-polarized scanning electron microscopy (spin SEM), where the secondary electron spin polarization is used as the image signal, is a novel technique for magnetic domain observation. Since its first development by Koike and Hayakawa in 1984, several laboratories have extensively studied this technique and have greatly improved its capability for data extraction and its range of applications. This paper reviews the progress over the last few years.Almost all the high expectations initially held for spin SEM have been realized. A spatial resolution of several hundreds angstroms has been attained, which is nearly one order of magnitude higher than that of conventional methods for thick samples. Quantitative analysis of magnetization direction has been performed more easily than with conventional methods. Domain observation of the surface of three-dimensional samples has been confirmed to be possible. One of the drawbacks, a long image acquisition time, has been eased by combining highspeed image-signal processing with high speed scanning, although at the cost of image quality. By using spin SEM, the magnetic structure of a 180 degrees surface Neel wall, magnetic thin films, multilayered films, magnetic discs, etc., have been investigated.
Characterisation of planar crystal defects in Y2Fe17Cx (0.6 ≤ x ≤ 1.6) magnetic material by High Resolution Electron Microscopy
Authors: Coene W. , Hakkens F. , Jacobs T.H. , Buschow K.H.J. 
Published: June 2020

Intermetallic compounds of the type RE2Fe17Cx (RE= rare earth element) are promising candidates for permanent magnets. In case of Y2Fe17Cx, the Curie temperature increases from 325 K for x =0 to 550 K for x = 1.6 . X ray and electron diffraction reveal a carbon - induced structural transformation in Y2Fe17Cx from the hexagonal Th2Ni17 - type (x < 0.6 ) to the rhombohedral Th2Zn17 - type ( x ≥ 0.6). Planar crystal defects introduce local sheets of different magnetic anisotropy as compared with the ordered structure, and therefore may have an important impact on the coercivivity mechanism .High resolution electron microscopy ( HREM ) on a Philips CM30 / Super Twin has been used to characterize planar crystal defects in rhombohedral Y2Fe17Cx ( x ≥ 0.6 ). The basal plane stacking sequences are imaged in the [100] - orientation, showing an ABC or ACB sequence of Y - atoms and Fe2 - dumbbells, for both coaxial twin variants, respectively . Compounds resulting from a 3 - week annealing treatment at high temperature ( Ta = 1000 - 1100°C ) contain a high density of planar defects.
Electron-beam patterning of materials with nanometer resolution
Authors: Berger S.D. , Macaulay J.M. , Brown L.M. 
Published: June 2020

It was first reported in 1978 that intense electron irradiation of thin films of NaCl leads to the formation of holes with a diameter of the order of the probe. Since that time the same phenomena has been observed in a variety of materials, typical examples being AlF3, MgO and Al2O3. Quantitative and qualitative descriptions of the damage have been given by a number of workers in an attempt to understand the underlying mechanisms. While groups of chemically or structurally similar materials often show the same general sequence of events in the hole formation process, it is a common observation that polymorphs or different preparation techniques result in very different behavior, Furthermore, examples of hole formation have been given which appear to show characteristics specific to that material system.In an effort to gain insight into the hole formation process we decided to concentrate on a set of observations which are reasonably common.
The buckling of thin EM specimens
Authors: Thölén A.R. 
Published: June 2020

Thin electron microscope specimens often contain irregular bend contours (Figs. 1-3). Very regular bend patterns have, however, been observed around holes in some ion-milled specimens. The purpose of this investigation is twofold. Firstly, to find the geometry of bent specimens and the elastic properties of extremely thin foils and secondly, to obtain more information about the background to the observed regular patterns.The specimen surface is described by z = f(x,y,p), where p is a parameter, eg. the radius of curvature of a sphere. The beam is entering along the z—direction, which coincides with the foil normal, FN, of the undisturbed crystal surface (z = 0). We have here used FN = [001]. Furthermore some low indexed reflections are chosen around the pole FN and in our fcc crystal the following g-vectors
are selected:
SEM study of quartz grains from recent sediments: Western Iraq
Authors: Al-Kufaishi F. 
Published: June 2020

Two localities (Al-Marij and Laik) were selected to investigate the type of Quartz Grains from crustal material formed by evaporation of waters discharged by springs in Hit area, western Iraq, Previous studies on the crustal material (1,2) showed that the water discharged by these springs are associated with Abu-Jir fault system which run parallel to the Euphrates river,Factor analyses of the crustal and soil materials (50 samples analysed for 16 variables)(2) showed five factors; the first factor includes SiO2, Al2O3 and TiO2 with positive factor loading, and CaO, L.O.I. with negative loading and hence lead to the conclusion that the distribution of these variables is a reflection of transported clay material.This study concentrates on the use of SEM to investigate the contribution of Quartz grains found in the crustal material on two selected
sites.
Modelling of the electron beam scattering by fine-dispersed structures and calculation of topographical contrast of cathodoluminescent images in the SEM
Authors: Viskov M.V. , Nikolaev A.G. , Obyden S.K. , Saparin G.V. , Meleshkin S.M. 
Published: June 2020

A three-dimensional model of the scattering of a high-energy electron beam in a fine-dispersed structure (FDS) is developed. The model is intended for calculating, by the Monte-Carlo method, the color and black-and-white contrast of the image formed in the course of investigations of powdered structures in the cathodoluminescence (CL) mode in the SEM. The theory is developed in the approximation of an infinitely thin electron beam, which limits the minimum sizes of FDS crystals by the value of the order of 10μm under the experimental conditions (the electron beam diameter of 0.8 to 1.0 μm).The model takes account of: 1) elastic and inelastic interactions, and the absorption of the electrons of the primary beam scattered during the whole succession of the acts of interaction with FDS crystals; 2) secondary electron emission: the “birth”, elastic and inelastic scattering, and the absorption of secondary electrons during the whole succession of the acts of interaction with FDS crystals; 3) a change in the intensity and wavelength of the detected monochromatic CL-radiation of each of the FDS crystals with allowance made for the elastic and Raman scattering and the absorption of CL photons; 4) a stochastic character of the volume distribution of the FDS crystals, as well as their random orientation and possible defects of their shape; the requirement of the identical size of the crystals being kept in force; 5) the geometry of the light-collecting system, namely, the angular aperture of the luminescence collector.