bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Resolution Transmission Electron Microscopy of an automobile catalytic converter
Authors: Malm Jan-Olle , Bovin Jan-Olov 
Published: June 2020

Understanding of catalytic processes requires detailed knowledge of the catalyst. As heterogeneous catalysis is a surface phenomena the understanding of the atomic surface structure of both the active material and the support material is of utmost importance. This work is a high resolution electron microscopy (HREM) study of different phases found in a used automobile catalytic converter.The high resolution micrographs were obtained with a JEM-4000EX working with a structural resolution better than 0.17 nm and equipped with a Gatan 622 TV-camera with an image intensifier. Some work (e.g. EDS-analysis and diffraction) was done with a JEM-2000FX equipped with a Link AN10000 EDX spectrometer. The catalytic converter in this study has been used under normal driving conditions for several years and has also been poisoned by using leaded fuel. To prepare the sample, parts of the monolith were crushed, dispersed in methanol and a drop of the dispersion was placed on the holey carbon grid.
Optimum collection angle for detection of small catalyst particles in high-angle dark-field Scanning Transmission Electron Microscopy
Authors: Amali Adam , Rez Peter 
Published: June 2020

Since Crewe et al demonstrated the detection of single heavy atoms on thin carbon support films, there has been considerable interest in the use of high angle annular dark field detectors(HADD) to study particles in the subnanometer size range. A recent contribution to this subject is the work of Treacy and Rice.Increased interest in this technique can be attributed to the minimization of diffraction and phase contrast effects in the imaging of small atom catalyst particles .In this study we calculate the expected signal using realistic electron scattering cross sections. For the high angle dark field considered, it is reasonable to assume single scattering and to consider dynamical effects averaged out by the averaging over annular aperture.The electron scattering amplitude used is given by the Mott formula;
In situ TEM study of the Ru-RuOx/TiO2 catalyst for low temperature methanation of carbondioxide
Authors: Ruterana P. , Buffat (I2M) P-A. , Thampi K.R , Graetzel (ICP) M. 
Published: June 2020

The Ru-RuOx/TiO2 catalyst has been shown to be able to produce methane from hydrogen and carbon dioxide at room temperature and atmospheric pressure at reasonably high rates (TOF: 10-6 at 25C and 10-4 at 90C). The best results were obtained using the P25 support (Degussa 80% anatase and 20% rutile) in the 55-60 m2/g surface area range. The optimal loading for the metal is 3.8% Ru metal.We found that in the most active catalysts, the metal (>90%) is selectively loaded on the rutile crystallites. This distribution shows up clearly in a 500C reduced sample (fig.l) in which the size of the metal particles has increased.
EM study of carbon shell formation on Ni/MgO catalyst
Authors: Tracz E. , Borowiecki T. , Scholz R. 
Published: June 2020

Previous HREM studies have treated the creation of filamentous carbon deposits during the steam reforming of n-butane reaction on Ni/MgO catalysts at temperatures 673 K to 953 K. At highest temperatures besides tubular filaments so-called carbon shells are generated enclosing Ni particles. The mechanism of carbon filament growth has extensively been discussed by several authors and seems to be understood. The creation of shells, on the other hand, has rarely been described up to now. The frequent observation of some intermediate forms between carbon tubes and shells attracted our interest in this problem.Common carbon tubes are formed behind Ni particles whereas the intermediate forms under discussion have the following essential appearances :- Tubes containing Ni inclusions along the tube besides Ni particles on both ends of the tube (Fig. 1).- The Ni particles at the ends of the tubes are either both enclosed by shell-like carbon structures, or one of these particles is partly free of carbon such as the tip particles in common tubes.- One part of these forms often looks like a chain of carbon shells always including Ni particles (Fig. 1, 4 ).- The respective Ni particles appear in various shapes (Fig. 1-5) often drop-like (Fig. 3, 4) or elongated (Fig. 1, 4), suggesting proceeding transformations.
Low-energy surfaces and interfaces in aluminum nitride
Authors: McKenan Stuart , Grant Norton M. , Barry Carter C. 
Published: June 2020

As a potential semiconductor substrate material, aluminum nitride (AIN) has recently become the subject of much research. In particular, the nature of the defects which occur in this material is yet to be fully understood. The mechanical strength, high thermal conductivity and large electrical resistivity and a relatively small thermal expansion coefficient, of the defect-free, single crystal material make it extremely well suited for use as a semiconductor substrate material. The polycrystalline AIN contains grain- boundaries, second phases, and many internal defects, all of which may produce a degradation in the physical properties of the substrate. The characterization of these microstructural defects in this material is obviously necessary in the understanding of the properties of the polycrystalline material.AIN has the hexagonal, wurtzite structure rather than the cubic structure of the more common semiconductors. It is also a polar material, and many of the polar surfaces are low-index planes. Grain boundaries (and other interfaces) composed of different crystallographic planes may be expected to have different physical and electrical properties. This effect of the crystallography has been investigated by TEM in two ways; firstly, grain boundaries in polycrystalline AIN have been characterized.
Transmission Electron Microscopy studies of the structure of martensitic interfaces in Cu-Zn: Diffraction contrast
Authors: Chen F.-R. , Olson G. B. 
Published: June 2020

A Cu-38.6%Zn alloy was treated at 870°C and quenched in ice brine(10% NaOH) to produce martensitic transformation. The parent phase is bcc structure and the martensite phase is 9R close-packed structure. The orientation relationship of the parent phase and martensite was determined by the Kikuchi pattern and diffraction pattern. The experimental lattice deformation matrix can then be deduced from the orientation relationship and assumed correspondence. The lattice deformation matrices determined from experiment and calculated from CRAB martensite crystallography theory are as follows:As shown in Figure 1, a set of dislocations is observed in the martensitic interface whose Burgers vector is determined to be l/3[101]b by the two beam technique. The direction and the average spacing of these dislocations determined from experiment are [.49 .
.47]b and 5±1nm respectively. This set of dislocations is consistent with the lattice invariant shear l/3[101]b on the (
01)b plane with the magnitude 0.022 used in the CRAB martensite crystallography which corresponds to an anticoherency dislocation array with the spacing of 7.75nm and in the direction [.514,.
,.514]b. The habit plane determined from experiment is (.13,.65,.75 )b and close to (.13,.68,.72)b from the prediction of CRAB martensite crystallography.
An HREM study of interface structure between S’ phase and Al matrix in 2024 alloys
Authors: Ye H. Q. , Hu K.Y. 
Published: June 2020

The precipitate in 2024 alloys containing Cu and Mg as the main strengthening elements is the S’ phase, which belongs to an orthorhombic system with the Cmcm space group and lattice constants of a=0.400 nm, b=0.923 nm and c=0.714 nm. The orientation relationships between the S’ phase and matrix were established by x-ray diffraction data as follows: [100]s’ //[100], [010]s’ //[021], [001]s’ //[01
]. Recent HREM observations on the crystallography and morphology of the S’ phase have been reported. In this work Hr images of the S’ -matrix interface are presented with suitable resolution power.A 2024 Al alloy containing 4.43wt% Cu, 2.0wt% Mg and 0.53wt% Mn was treated at 495°C for 1h and quenched in water. Aging treatments were carried out at 190°C for 6h and 24h, respectively. Specimens were examined on the JEOL 200CX and 4000EX microscopes, the later of which has interpretable resolution of about 0.17 nm.
HREM study of interface of intermetallic matrix composites TiAl and Ti2AlN prepared by a combustion-reaction method
Authors: Sukedai Eiichi , Mabuchi Hiroshi , Hashimoto Hatsujiro , Nakayama Yutaka 
Published: June 2020

Intermetallic compound TiAl has characteristic properties of light and high strength at elevated temperature but poor in ductility and toughness at room temperature. To improve these properties, recently this compound was made as a composite material containing a second phase such as boride. Present authors have developed a new combustion-reaction method to make a composite material under a nitrogen atmosphere and it was found that the composite material has good ductility, toughness and strength at both room and elevated temperatures(400MPa at 1173K). In the present paper, the structures of matrix TiAl and Ti2AlN were investigated in atomic scale by using high resolution electron microscopy.Ti powder (99.5% purity) and Al powder (99.5% purity) were mixed into the stoichiometric composition of TiAl. Using these powders, the composite material of TiAl (matrix) and Ti2AlN was prepared by the combustion-reaction method under the nitrogen atmosphere at 0.lMPa, which will be presented in details soon. Specimens were prepared by electro-polishing and observed by JEM-4000EX operated at 350kV.
HREM image contrast at the CoSi2/Si interface
Authors: de Jong A.F. , Bulle-Lieuwma C.W.T. 
Published: June 2020

Epitaxial layers of CoSi2 can be grown on both (111) and (001) substrates, or fabricated as a buried layer by ion implantation. The atomic structure at the interface is of interest because it determines the Schottky barrier height and because it is Coupled to the types of dislocations which are found. High-resolution electron microscopy (HREM) combined with image simulation is used to investigate the atomic structure at the interface. Detailed image simulations are needed to investigate under which imaging conditions the (small) differences between the models are visible. In this contribution an analysis is given of the HREM contrast within the CoSi2 unit cell, using a linear imaging theory. The results are used to investigate the various models proposed for the CoSi2/Si (111) interface.In the < 110 > imaging orientation the contrast in HREM images of CoSi2 is dominated by (200) and(111) fringes.
Fine structure and properties of defects in naturally occurring silicates and oxides
Authors: Veblen David R. 
Published: June 2020

Extended defects and interfaces control many processes in rock-forming minerals, from chemical reactions to rock deformation. In many cases, it is not the average structure of a defect or interface that is most important, but rather the structure of defect terminations or offsets in an interface. One of the major thrusts of high-resolution electron microscopy in the earth sciences has been to identify the role of defect fine structures in reactions and to determine the structures of such features. This paper will review studies using HREM and image simulations to determine the structures of defects in silicate and oxide minerals and present several examples of the role of defects in mineral chemical reactions. In some cases, the geological occurrence can be used to constrain the diffusional properties of defects.The simplest reactions in minerals involve exsolution (precipitation) of one mineral from another with a similar crystal structure, and pyroxenes (single-chain silicates) provide a good example. Although conventional TEM studies have led to a basic understanding of this sort of phase separation in pyroxenes via spinodal decomposition or nucleation and growth, HREM has provided a much more detailed appreciation of the processes involved.
Dislocation loops on cube planes in long range ordered Cu3Au
Authors: Rentenberger Ch. , Karnthaler H. P. 
Published: June 2020

Long range ordered Cu3Au exhibits like other L12 ordered alloys an anomalous increase in the yield strength with increasing temperature. Dislocations which have an antiphase boundary APB fault on the cube plane play a main role in theoretical models that have been proposed to explain this anomaly. In this investigation two types of loops are studied that occur on cube planes. From the measured dissociaton widths of the superlattice dislocations the value of the APB energy can be determined. Different values have been achieved for octahedral and cube planes; they can be compared with previous measurements and with the theoretical models.Single crystals of Cu3Au were grown under vacuum and subsequently annealed to achieve a high degree of order and a large domain size. The crystals were deformed in tension at room temperature. For the TEM investigation discs were cut parallel to the primary octahedral glide plane and to the cube cross slip plane. The preparation of the thin foils is rather difficult because of the large gold content.
HREM study on the structure of SrMnO3-x with planar defect
Authors: Shibahara Hiroyasu 
Published: June 2020

The system of SrMnO3-x is known to be layered structure closely related to that of perovskite with oxygen deficiency and based on a stacking of close- packed SrO3 layers with Mn metals occupying interlayer octahedral sites, SrMnO3 possesses a 4-layer structure with hexagonal stacking (sequence of “ABAC”) at normal pressure, and through a 6-layer structure (“ABCACB”) transform into a 3-layer structure with cubic stacking at higher pressure, Based on the observed images with HREM (JEM-2000EX) showing an irregular stacking along c-axis, the distribution and the origin of planar defect were discussed.Specimens of SrMnO3-x were prepared by the conventional solid-state reaction technique . The typical observed image of 4H structure along 010 direction is shown in Fig.l together with the calculated image. The planar defects were often observed in the sample as shown in Fig.2, in which they represent a bright contrast. The defects were classified by their characteristic in image contrast into the three classes (type A,B and C), which are indicated by the marks in Fig.2.
An in-situ TEM study on the slip activation across grain boundaries
Authors: Lee T. C. , Robertson I. M. , Birnbaum H. K. 
Published: June 2020

The movement of lattice dislocations in a polycrystalline material is usually impeded by the existence of grain boundaries. Depending on the local chemistry and the structure of the boundary, this impediment (or the interaction of dislocations and grain boundaries) can create dislocation pile- ups and eventually lead to one of the several possible reactions: 1) dislocations can be transferred directly through the grain boundary, 2) dislocations can be absorbed and become grain boundary dislocations, 3) dislocations can be ejected back into their original grain, 4) dislocations can be accommodated in the grain boundary, followed by the emission dislocations into the adjoining grain or 5) nucleation of a crack at or near the intersection of the dislocation pile-up and the grain boundary.In order to understand the mechanism of the these interactions and their sensitivity to the chemistry of the grain boundary, the in-situ TEM straining technique has been used. The material studied were 310 stainless steel, hyper- and hypo-stoichiometric Ni3Al with and without boron.
Identification of defects induced by heavy metal contamination on Si(100) surface using TEM
Authors: Sadamitsu Shinsuke , Sasaki Ayako , Hourai Masataka , Sumita Shigeo , Fujino Nobukatsu 
Published: June 2020

It is well known that heavy metallic contaminations are harmful to the performance of silicon devices. There are several investigations about the precipitation behaviors of heavy metals on Si wafers. In this study, the observations of transmission electron microscopy (TEM) were carried out to identify defects induced by intentional Cu, Ni and Fe contamination on Si(100) surface.P-doped 5-12 Ω·cm, 5inch-diameter CZ-Si(100)wafers, with a mirror polished front surface and only chemically etched back surface, were used. The front surfaces of wafers were contaminated quantitatively by the technique proposed previously. The concentrations of each element on the surface were determined with an atomic absorption spectrophotometer. Cross-sectinal and plane TEM observations were conducted with a Hitachi H-9000 at 300KV. The conditions of annealings are shown in Fig.1.When the wafer was contaminated with Cu, colony precipitates were observed within a thin region near an interface of Si and SiO2 formed during the annealing. Each precititate was the same crystallographic orientaion and lies along Si(110) plane(Fig.2).
Application of Electron Microscopy for the detection of point defects in MBE GaAs layers grown at low temperature
Authors: Liliental-Weber Zuzanna 
Published: June 2020

Integration of GaAs devices is a challenging problem due to the lack of stable natural oxides which could isolate devices from one another. This problem is commonly solved by ion implantation, introducing point defects which can compensate impurity-related shallow donors or acceptors to make this material highly resistive. Recently, another approach was found: growing GaAs buffer layers at low temperature (∽ 200°C) removes all sidegating effects and so achieves effective device isolation. Such layers exhibit high resistivity, which is sustained even after annealing at 600°C. Own investigations by analytical electron microscopy showed these as-grown layers to be very As rich. Electron paramagnetic resonance and optical absorption studies detected AsGa antisite defects in the low-temperature buffer layers, in concentrations up to 1020 cm-3. X-ray diffraction revealed an 0.1 % increase in the lattice parameter of the epitaxial layers. After annealing at 600°C, the lattice parameter of the layers decreases to the substrate value?Transmission electron microscopy of these layers shows that their perfection is very sensitive to growth temperature and layer thickness. The layers grown below 200°C show specific defects with noncrystalline core surrounded by dislocations, stacking faults and microtwins.
HRTEM and CTEM study of differently lattice-mismatched InxGa1-xAs/InP heterostructures grown by VPE
Authors: Frigeri C. , Attolini G. , Pelosi C. , Corticelli F. 
Published: June 2020

InxGa1-xAs/InP heterostructures are used for optical communication systems. In order to establish the dependence of the structural defects on the growth conditions, differently lattice- mismatched samples have been characterized by both CTEM and HRTEM. The InGaAs layers were grown by hydride Vapor Phase Epitaxy on (001) oriented sustrates. Different layer mismatch (composition) was obtained by changing the GaCl flow in the deposition zone whereas the AsH3 and InCl flows were kept constant. A JEOL 2000 FX TEM with a point-to-point resolution of 0.31 nm at the Scherzer defocus of - 110 nm was employed. Both plan-view and cross-sectional specimens were investigated.The lattice-matched layers (x=0.53) were nearly defect-free even at the interface to the substrate as shown by the axial illumination HRTEM image given in Fig. 1. Different type of defects were observed in the lattice-mismatched layers depending on whether the mismatch ε was negative or positive. For negative lattice-mismatch the defects were mostly pyramidal stacking faults in a quite high density even for small mismatch as shown in Fig. 2 for a layer with ε= - 0.16% (x=0.51).
Nucleation mechanism of misfit dislocations in multi-quantum wells
Authors: Zou J. , Cockayne D.J.H. , Sikorski A. , Usher B.F. 
Published: June 2020

A series of plan-view and cross-section samples of multi-quantum wells (MQWs) consisting of 32nm GaAs and 10.5nm In0.15Ga0.85As grown by molecular beam epitaxy on GaAs substrates were examined by TEM. Tne number of periods (n) of the MQWs were 3, 6, 12, 24, and 48. The results showed that for n smaller than or equal to 12 periods, almost all misfit dislocations (MDs) were found near the epitaxial surface (see figure 1) which is far away from the interface between the MQWs and the substrate; but for n equal to or larger than 24 periods, most MDs were observed at the bottom interface between the MQWs and the substrate (shown in figure 2).To explain these observations, a new nucleation mechanism for the MDs has been derived from energy considerations, based on the theory of the critical thickness of the half circular dislocation loop (HCDL) in a single epitaxial layer and the strain contribution in the MQWs.
Inclusion observation and AEM study of new type nonlinear optical crystal β-BaB2O4
Authors: Wen Liu , Minrong Gao 
Published: June 2020

It is well known that β-BBO is a new type nonlinear optical crystal discovered in our institute and now β-BBO is widely used in the fields of laser and nonlinear optics.However,there are still some inclusions in β-BBO crystal grown by flux method.Using AEM technique,we have studied the shape,composition and structure of inclusions which is very helpful to the explanation of the formation of inclusions.Under optical microscope,the inclusions appear to be irregular in shape and there are some micro-cracks extending to the substrate in the boundary of large inclusions.Under scanning electron microscope,they are spongy and consist of many irregular grains surrounded by voids(Fig.1).The backscattered electron image indicates that the distribution of barium in the inclusion is inhomogeneous(Fig.2).By using electron probe micro-analysis,we studied the impurities and their distribution in the inclusions and discovered that Na element is gathered in inclusions while Ba element is much less in inclusions than in substrate(Fig.3).The distribution of Na and Ba is also inhomogeneous in inclusions.