bluuebunny/crossref_metadata_2025 huggingface dataset:
In-situ observation of solid-state amorphization in a Ni/Ti multilayer
Authors: Wall Mark A. , Jankowski Alan F.
Published: June 2020

Solid-state amorphization between thin films of two pure crystalline metals that have a negative heat of mixing is shown by Schwartz. An isothermal anneal is used to amorphize a binary crystalline structure via interdiffusion of one species, preferentially into the other. We report a metallic-glass formation by solid state amorphization in a Ni/Ti multilayered structure by low temperature annealing in the electron microscope. TEM allows us to view the composition modulation and interfaces of the Ni/Ti multilayered structure in crossection. Crossectional TEM is regularly used to view the composition modulation and interfaces of thin films. A TEM fitted with a hot-stage sample holder makes it possible to heat the cross-sectioned multilayer in-situ and record the ensuing reaction at the Ni-Ti interfaces.

Ni/Ti multilayers with a period of 26 nm (55 at.pct. Ni) were fabricated by magnetron sputtering, the details and parameters are outlined elsewhere. TEM specimens were prepared for cross-section viewing with a technique similar to Bravman and Sinclair, in combination with encapsulating the epoxied pieces with in a metal tube as described by Newcomb, et al.
Effect of oxygen on the stability of 1-D Lps in Cu3Pd
Authors: Huang P. , Menon E. S. K. , Ceder G. , de Fontaine D.
Published: June 2020

The variety of ordered phases exhibited by Cu-Pd alloys has led many investigators to study it both experimentally and theoretically. Recently, we have determined the Cu-rich portion of the Cu-Pd phase diagram (Fig. 1) and indicated that the region denoted as 1-d LPS actually represents a large number of single phase fields of long period superstructures (LPS) separated by narrow two phase regions in agreement with theoretical calculations. Each single phase field would correspond to an LPS with a characteristic modulation period, which can be measured from the splitting of the 001 reflection in diffraction patterns. High resolution electron microscopy (HREM) studies on Cu-Pd alloys have revealed that the antiphase boundaries (APB) associated with the LPS formed at low temperatures exhibit a sharp character, while those in LPS equilibrated at high temperatures are diffuse. In a recent theoretical study on LPS, Ceder et al. pointed out that the pair interaction potential in reciprocal space, V(k), associated with Cu-Pd alloys shows a rather deep minimum which arises as a result of flat sections on the Fermi surface. Ordering concentration waves located away from the minimum of V(k) would quickly disappear at higher temperatures because of their higher contribution to the configuration energy, thus leading to the formation of a smooth modulation profile. Consequently, in selected area diffraction patterns (SAD), only first order satellites are expected. On the other hand, at lower temperatures, where the contribution from the ordering concentration waves away from the minimum in V(k) is also significant, higher order satellites should be observable in SAD patterns.
The role of TEM in the development of advanced materials
Authors: Loretto M H
Published: June 2020

In general the microstructural assessment of advanced materials can be satisfactorily assessed using optical and scanning electron microscopy together with X-ray diffraction. Transmission electron microscopy (TEM) is used only when the scale and nature of the information which can be obtained from TEM is appropriate. The aim of the present article is to highlight some examples of the unique role that TEM has played in the field of structural materials. Four areas will be discussed: metal matrix composites; precipitation in Al-Li based alloys; rapid solidification; intermetallics.

In the field of metal-matrix composites one of the most important aspects is nature of the bonding and interaction between the reinforcement and the matrix, and this is an area where the spatial resolution of analytical TEM is required in order to characterise any interaction. The recent work on Ti6A14V/TiC and Ti24All INb/TiC composites has illustrated this very clearly. Even after heat treatments of 50h at 1100°C the TiC appears to be unaffected as assessed by both optical and scanning electron microscopy. Only when TEM is used is it possible to see that there has been any interaction.
XTEM microscopy of martensitic transformations in noble gas implanted stainless steel
Authors: Johnson E. , Johansen A. , Sarholt-Kristensen L. , Gerritsen E. , Politiek J. , Keetels H.A.A. , Coene W.M.J.
Published: June 2020

Cross-sectional transmission electron microscopy (XTEM) has been used to study the microstructure of noble gas implanted austenitic stainless steels, and in particular to analyse the depth distribution of implantation induced martensite in relation to the general radiation damage distribution.

Large discs of low-austenitic stainless steels have been ion implanted with noble gases to fluences in the range l.1020 - 1.1021 m-2. Samples of the implanted discs for cross-sectional transmission electron microscopy (XTEM) were made by electroplating the implanted surface with a 3 mm thick layer of nickel, cutting 3 mm discs from the interface and electropolishing the discs to perforation using a Struers TENUPOL immersion jet apparatus.

In samples implanted with low fluences (1-1020 m-2) the implantation zone consists of a heavily damaged top layer containing a dense distribution of microscopic noble gas inclusions, which are visible in defocusing phase contrast. The inclusions are ∽ 3-5 nm in diameter, and the smallest inclusions contain noble gas in the solid phase.
Imaging of crystalline structure in thermotropic copolymers
Authors: Spontak Richard J. , Windle Alan H.
Published: June 2020

Electron-diffraction analysis and dark-field (DF) imaging of crystalline structure in highly-oriented polymers have been used effectively to discern structure-property relationships in these materials. Diffraction patterns of some thermotropic copolyesters, such as those composed of 4-hydroxybenzoic acid (B) and 2,6-hydroxynaphthoic acid (N) or those from N and terephthalic acid/hydroxyaniline (TA), exhibit sharp equatorial reflections, suggestive of finite intermolecular ordering, and aperiodic meridional maxima, indicative of random intramolecular sequencing (see inset of Fig. 1). However, diffraction analysis of a related thermotropic copolymer, composed of B and isophthalic acid/hydroquinone (IQ), reveals periodic meridional maxima and ill-defined equatorial reflections. DF imaging in conventional transmission electron microscopy is utilized here to permit accurate assessment of the crystallite morphologies in these two chemically-related families.

Samples of the B-N and N-TA materials were provided by the Hoechst-Celanese Corporation, and the B-IQ copolymer was supplied by ICI Advanced Materials. Electron-transparent films were produced by first heating a small chunk of each material on freshly-cleaved rocksalt to a predesignated temperature. The samples were then quickly sheared with a razor blade, and the resultant films were quenched on an aluminum block.
In-situ Electron Microscopy in catalysis research
Authors: Gai Pratibha L
Published: June 2020

The dynamic nature of surfaces and interfaces in catalytic oxides, and in metal particle catalysts on oxide supports, is of fundamental importance in heterogeneous catalysis. In-situ electron microscopy with a controlled environment has been used, together with other EM-based techniques, to obtain a better understanding of disorder under reaction conditions in these non-stoichiometric materials. It is important to recognize that the structure of the solid surface under reaction conditions may differ from that occurring under static conditions or in different atmospheres, including the usual EM high vacuum specimen environment.

Powders of co-precipitated silica supported copper-ruthenium are used in ethane hydrogenolysis; whilst Cu on alumina is used in methanol related catalysis and some power cells. The performance, sintering, metal-ceramic adhesion and fracture depend on the interface structures. They are controlled by chemical and other materials properties under working conditions Fig.1a and c show in-situ EM reaction sequences of Cu with amorphous alumina at ∼200°C in H2 and CO Fig.1c and d show the subsequent reaction of the particles in oxygen.
Controlling microvoid formation in TiO2(B) catalyst support
Authors: Reine Wallenberg L. , Sanati Mehri , Andersson Arne
Published: June 2020

It is known that the support may sometimes influence the performance of close-to-monolayer catalysts by formation of specific surface species of the active phase. For a 1.5 monolayer vanadium oxide catalyst, supported on TiO2B) which is a recently discovered form of titanium dioxide, an increase in conversion rate of more than 2 times was found compared to pure V2O5 in the case of ammoxidation of toluene. On investigation by High Resolution Electron Microscopy (HREM), it was found that a large number of sharply facetted voids, so called “negative crystals”, were present in the TiO2(B) support (Fig. 5). HREM stereo micrographs showed that the voids, 3-30 nm in size, were distributed throughout the bulk of the crystals.

In an attempt to open these voids to channels, which would give substantially larger specific surface area of the catalyst, the chemical composition of the starting material was varied.

The support was formed by calcining a mixture of KNO3 with TiO2 (anatase) at 950°C, which produces an intermediate support precursor.
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;
Systematic zone-Axis orientation of NM-scale particles for microdiffraction
Authors: Boyes E D , Hanna L
Published: June 2020

A VG HB501 FEG STEM has been modified to provide track whilst tilt [TWIT] facilities for controllably tilting selected and initially randomly aligned nanometer-sized particles into the high symmetry zone-axis orientations required for microdiffraction, lattice imaging and chemical microanalysis at the unit cell level. New electronics display in alternate TV fields and effectively in parallel on split [+VTR] or adjacent externally synchronized screens, the micro-diffraction pattern from a selected area down to <1nm2 in size, together with the bright field and high angle annular dark field [HADF] STEM images of a much wider [˜1μm] area centered on the same spot. The new system makes it possible to tilt each selected and initially randomly aligned small particle into a zone axis orientation for microdiffraction, or away from it to minimize orientation effects in chemical microanalysis. Tracking of the inevitable specimen movement with tilt is controlled by the operator, with realtime [60Hz] update of the target designation in real space and the diffraction data in reciprocal space. The spot mode micro-DP and images of the surrounding area are displayed continuously. The regular motorized goniometer stage for the HB501STEM is a top entry design but the new control facilities are almost equivalent to having a stage which is eucentric with nanometric precision about both tilt axes.
Electron Microscopy characterisation of fluorinated zeolites
Authors: Castaño V. , Vázquez A. , Saniger J. , Sánchez N. , Flores J.
Published: June 2020

Zeolites constitute one of today 's most important materials in Catalysis and their characterisation, in every respect, remains a challenge for scientists in the field. Generally speaking, zeolites can be classified as follows: a) High Si/Al ratio zeolites and b) Zeolites with a small Si/Al relationship. Obviously, many of the properties are quite different for the two types of zeolites since low Si/Al zeolites have less acidic sites of high catalytic strength. Thus, it is important to devise a simple and efficient way to modify low Si/Al zeolites to have higher Si to A1 ratios. One way for achieveing this is via the modification with F of 4A-type zeolites. Figures 1 and 2 show a comparative EDX analysis of an unchanged zeolite and of a fluorinated one, respectively. As can be observed there, the Si/Al ratio remains basically the same, result that is contrary to some previous reports which claimed a loss of A1 during the fluorination. High Resolution Electron Microscopy, on the other hand, shows interesting changes at the microstructural level since some amorphization of the fluorinated samples was detected, as can be observed in the digitally processed high resolution image of figure 3. From our electron microscopy studies we conclude that, for low-pressure fluorination conditions, the zeolites behaves as an inert support for the F whereas for higher pressures the F is incorporated to the zeolite structure
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.
Transmission Electron Microscopy studies of the structure of martensitic interfaces in Cu-Zn: HRTEM
Authors: Chen F.-R. , Olson G. B.
Published: June 2020

The crystallography and interfacial structure of martensite in Cu-38.6%Zn has been studied by conventional TEM and reported in these proceedings. The parent phase is bcc and the martensite phase has a 9R close-packed structure with the stacking order “ABC/BCA/CAB/A” normal to the c axis. Here, the bcc-9R interfaces are studied by using high resolution electron microscopy. The coherency dislocation/step structure of enclosed second phase particles has been treated by Olson and Cohen. The most significant coherency dislocation/step in an interface is formed by the intersection of interface and the most close-packed lattice plane which is nearly parallel to the interface. The average habit plane of martensite in Cu-38.6%Zn determined from experiment and CRAB crystallographic theory is very close to (4 21 22)b which is 7.6° away from the most close-packed lattice plane (011)b. Therefore, the best crystallographic direction for high-resolution electron microscopy studies is [01]b where the habit plane and the (011)b are all edge-on. Unfortunately, in this beam direction there is only one set of lattice fringes from both parent and martensite phases which can be resolved and they provide little information about interfacial structure. As shown in Figure 1 the high resolution images are therefore taken along the [11]b lattice invariant line (anti-coherency dislocation line) direction where the interfacial boundary and the internal stacking faults of the martensite are near edge-on. Figure 1 (a) and (b) are in the same area but taken with different defocus. These images were taken using the Berkeley ARM operated at 800 kv.
A technique for measuring small atomic displacements in HREM images
Authors: Dahmen U. , Hetherington C.J.D. , Westmacott K.H.
Published: June 2020

An important problem in materials science is the measurement of elastic strain fields, lattice rotations and rigid body shifts. High resolution microscopy is a simple and direct means of mapping displacement fields near defects, interfaces or precipitates. Large and highly localized atomic relaxations such as those found near the core of dislocations or structural units in grain boundaries are sensitive to thickness and defocus conditions and must be interpreted with the use of image simulations. However, displacements of small magnitude or displacement fields that vary slowly enough to allow only a gradual change of the periodic interatomic distance avoid artifacts caused by oscillations of the contrast transfer function. Such displacements are accurately reflected in the position of atomic column images under most imaging conditions and can be measured directly and without the aid of image simulations. Spot-to-spot measurements can be performed directly on a high resolution image, but such measurements are tedious and of low accuracy. Plane-to-plane measurements are more accurate but require the use of a microdensitometer. The present contribution introduces an alternative method based on interference effects between two overlaid images or lattices to produce Moiré patterns that display the displacement field in a graphic and accurate manner. The method makes use of the fact that small violations of perfect translation, rotation and mirror symmetries will give rise to large changes in the periodicity of the Moirés.
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.
A bright-field method for determining the nature of stacking faults in FCC materials which is applicable to thin crystals
Authors: Kim H. S. , Sheinin S. S.
Published: June 2020

Two well established methods for determining whether a stacking fault is intrinsic or extrinsic have been given in the literature. Both methods involve the use of asymmetrical dark field images of stacking faults obtained under strong beam diffraction conditions. The asymmetry in these images is due to the effects of anomalous absorption and, therefore, this asymmetry can only be observed in thicker regions of a specimen. As a result these methods are more difficult to apply to crystals which have low absorption coefficients such as silicon. The authors of this paper have shown that an asymmetry found in bright field images can be used to determine the nature of a fault. This asymmetry does not depend on the effects of absorption and, therefore, can be used to determine the nature of a fault under conditions which make the conventional techniques difficult or impossible to use. The asymmetry in bright field images referred to above is associated with the inclination of the entrance surface of the specimen and/or the stacking fault plane to the incident electron beam. In the calculation of contrast obtained in the stacking fault image, this implies that symmetrical Laue diffraction conditions cannot be assumed and the column approximation cannot be made. An illustration of the asymmetry referred to above can be seen by comparing Figs. la and b.
Radiation-induced disordering and amorphization—An in situ HVEM study of uranium silicide with comparison to natural processes in zirconolite
Authors: Birtcher R. C. , Wang L. M. , Allen C. W. , Ewing R. C.
Published: June 2020

We present here results of in situ TEM diffraction observations of the response of U3Si and U3Si2 when subjected to 1 MeV electron irradiation or to 1.5 MeV Kr ion irradiation, and observations of damage occuring in natural zirconolite. High energy electron irradiation or energetic heavy ion irradiation were performed in situ at the HVEM-Tandem User Facility at Argonne National Laboratory. In this Facility, a 2 MV Tandem ion accelerator and a 0.6 MV ion implanter have been interfaced to a 1.2 MeV AEI high voltage electron microscope. This allows a wide variety of in situ experiments to be performed with simultaneous ion irradiation and conventional transmission electron microscopy. During the electron irradiation, the electron beam was focused to a diameter of about 2 μ.m at the specimen thin area. The ion beam was approximately 2 mm in diameter and was uniform over the entire specimen. With the specimen mounted in a heating holder, the temperature increase indicated by the furnace thermocouple during the ion irradiation was typically 8 °K.
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.
Multiple phase transitions investigated by high-speed TEM
Authors: Bostanjoglo Oleg , Thomsen-Schmidt Peter
Published: June 2020

Thin GexTe1-x (x = 0.15-0.8) were studied as a model substance of a composite semiconductor film, in addition being of interest for optical storage material. Two complementary modes of time-resolved TEM were used to trace the phase transitions, induced by an attached Q-switched (50 ns FWHM) and frequency doubled (532 nm) Nd:YAG laser. The laser radiation was focused onto the specimen within the TEM to a 20 μm spot (FWHM). Discrete intermediate states were visualized by short-exposure time doubleframe imaging /1,2/. The full history of a transformation was gained by tracking the electron image intensity with photomultiplier and storage oscilloscopes (space/time resolution 100 nm/3 ns) /3/. In order to avoid radiation damage by the probing electron beam to detector and specimen, the beam is pulsed in this continuous mode of time-resolved TEM,too.Short events ( <2 μs) are followed by illuminating with an extended single electron pulse (fig. 1c)
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).
Effect of temperature on defect formation during oxygen implantation of silicon-on-insulator material
Authors: Jung C. O. , Visitsemgtrakul S. , Krause S.J. , Roitman P. , Cordts B.
Published: June 2020

Oxygen implanted silicon-on-insulator material, SIMOX, (Separation by IMplanted Oxygen) provides improved speed and radiation hardness over bulk silicon for integrated circuits which are built on the thin superficial Si layer above the buried oxide layer. A high quality superficial Si layer is required, but may be degraded by high defect densities of 109 to 1010 cm-2 in annealed SIMOX. Defect densities have been reduced down to 106cm-2 or less. They were achieved with a final high temperature annealing step (1300-1400°C) in conjunction with: a) high temperature implantation or; b) channeling implantation or; c) multiple cycle implantation. The defect structure developed during implantation, which is strongly affected by temperature, plays a significant role in the defect structure in the annealed material. In this work we are reporting on the effect of implantation temperature on defect formation and also some new details on the structure of the defects that are present.
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.
Characterisation of multilayer materials using a position-sensitive atom probe
Authors: Mackenzie RAD , Smith G D W , Cerezo A. , Liddle J A , Grovenor CRM , Hetherington M G
Published: June 2020

The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, permits both chemical and spatial information in three dimensions to be recorded from a small volume of material. This technique is particularly applicable to situations where there are fine scale variations in composition present in the material under investigation. We report the application of the POSAP to the characterisation of semiconductor multiple quantum wells and metallic multilayers.

The application of devices prepared from quantum well materials depends on the ability to accurately control both the quantum well composition and the quality of the interfaces between the well and barrier layers. A series of metal organic chemical vapour deposition (MOCVD) grown GaInAs-InP quantum wells were examined after being prepared under three different growth conditions. These samples were observed using the POSAP in order to study both the composition of the wells and the interface morphology. The first set of wells examined were prepared in a conventional reactor to which a quartz wool baffle had been added to promote gas intermixing. The effect of this was to hold a volume of gas within the chamber between growth stages, leading to a structure where the wells had a composition of GalnAsP lattice matched to the InP barriers, and where the interfaces were very indistinct. A POSAP image showing a well in this sample is shown in figure 1. The second set of wells were grown in the same reactor but with the quartz wool baffle removed. This set of wells were much better defined, as can be seen in figure 2, and the wells were much closer to the intended composition, but still with measurable levels of phosphorus. The final set of wells examined were prepared in a reactor where the design had the effect of minimizing the recirculating volume of gas. In this case there was again further improvement in the well quality. It also appears that the left hand side of the well in figure 2 is more abrupt than the right hand side, indicating that the switchover at this interface from barrier to well growth is more abrupt than the switchover at the other interface.
Morphological and structural study of integrated circuits using XTEM and HREM
Authors: Bharadwaj L.M. , Gantcheva L.M. , Simov S. , Balossier G. , Faure J. , Bonhomme P.
Published: June 2020

There is increasing interest in the use of cross-sectional transmission electron microscopy (XTEM) to understand fundamental and technological problems associated with fabrication of integrated circuit (IC). This is because with XTEM it is possible to obtain exact morphological configuration and structure at atomic level of different layers and interfaces. For the study of a MOS device we used slightly modified XTEM specimen preparation technique than reported by other authors. To monitor region of interest during mechanical preparation two techniques were used as illustrated in Fig.1. First by glueing two slabs (10 × 4 mm2) of wafer each exactly identical in terms of geometrical dimension and device features and second by glueing a transparent glass plate on the top of wafer. The epoxy has higher ion beam etching rate than other materials so to obtain uniform thinning, ion beam was centered slightly away from the epoxy line . The thinned specimens were observed under Philips CM-30 electron microscope.
Effect of annealing ambient on the precipitation processes in oxygen-implanted silicon on-insulator material
Authors: Roitman P. , Simons D.S. , Visitserngtrakul Supapan , Jung C.O. , Krause S J.
Published: June 2020

In the last decade, oxygen implanted silicon-on-insulator material (SIMOX: Separation by IMplantation of OXygen) has been extensively studied, due to its potential advantages of increased speed and radiation hardness in integrated circuits. SIMOX material requires two processing steps: first, implantation of a high dose of oxygen to form a buried oxide layer below a thin, top silicon layer; second, a high temperature anneal in an inert gas atmosphere to remove implantation damage and oxide precipitates. Most earlier studies investigated the effect of annealing temperature and time, but did not consider the effect of gas ambient. The effect of nitrogen and argon on the oxide-precipitate formation in bulk silicon has been established. Raider et al. found that in annealing of bulk silicon, nitrogen can diffuse to an oxide-silicon interface and chemically react with silicon. The nitrogen-containing layer acts as a barrier to further oxidation. Consequently, nitrogen influences the growth kinetics of the thermal oxide while annealing in an argon ambient does not. This should apply to SIMOX as well. We have, therefore, investigated the effect of nitrogen and argon ambient on the oxide-precipitate removal during annealing of SIMOX material.