bluuebunny/crossref_metadata_2025_split huggingface dataset:
TEM study of surface modification of sapphire by pulsed-laser irradiation
Authors: Cao Siqi , Pedraza A. J. , Allard L. F. 
Published: June 2020

The mechanical strength of a metal-ceramic couple is primarily determined by the bonding force developed at the interface. The nature and magnitude of these forces depend upon the characteristics of the couples as well as the deposition process. In particular, noble metals show very poor adhesion onsapphire substrates in the as-deposited condition. However, the bonding of a metal-ceramic couple canbe improved by various surface modification methods such as laser irradiation and ion bombardment. Pedraza et al. studied the adhesion enhancement of metallic films ion-beam sputter-deposited on ceramicsubstrates. It was found that a very strong increase in the adherence of the metallic films could be achieved if the substrate had been laser-irradiated prior to film deposition. In this paper, the interfacial microstructure of cross-sectional samples of Au films deposited on laser irradiated sapphire was examined by TEM in order to gain some insight into the bonding mechanisms of these couples.Optically polished c-axis sapphire substrates were laser-irradiated in air with twenty sequential pulses of 3 J/cm2 each.
Morphology and development of flow-pattern defect with extended nonagitated Secco etching
Authors: Pan Y. 
Published: June 2020

The D defect, which causes the degradation of gate oxide integrities (GOI), can be revealed by Secco etching as flow pattern defect (FPD) in both float zone (FZ) and Czochralski (Cz) silicon crystal or as crystal originated particles (COP) by a multiple-step SC-1 cleaning process. By decreasing the crystal growth rate or high temperature annealing, the FPD density can be reduced, while the D defectsize increased. During the etching, the FPD surface density and etch pit size (FPD #1) increased withthe etch depth, while the wedge shaped contours do not change their positions and curvatures (FIG.l).In this paper, with atomic force microscopy (AFM), a simple model for FPD morphology by non-crystallographic preferential etching, such as Secco etching, was established.One sample wafer (FPD #2) was Secco etched with surface removed by 4 μm (FIG.2). The cross section view shows the FPD has a circular saucer pit and the wedge contours are actually the side surfaces of a terrace structure with very small slopes. Note that the scale in z direction is purposely enhanced in the AFM images. The pit dimensions are listed in TABLE 1.
Microstructural and magneto-optical characterization of ferrimagnetic multilayered thin-film rare-earth iron garnet heterostructures
Authors: Simion B. M. , Ramesh R. , Marinero E. , Pfeffer R. L. , Thomas G. 
Published: June 2020

The continuous demands of the computer industry for increased reliability, portability, and density of storage media, has opened a new chapter in the magnetic recording research, by focusing on the viability of magneto-optical materials for storage. Several materials are considered presently to be at the forefront of this new quest: ternary rare-earth transition-metal alloys (such as GdTbFe or TbFeCo), garnets, and Co/Pt or Co/Pd mutilayers. Of these, the ferrimagnetic garnets, due to their relatively flexible structure, may accommodate a large number of substituting ions, allowing thus for a very good control of their magnetic and magneto-optical properties. The good results obtained during thegrowth of epitaxial superconducting oxide thin films by pulsed laser deposition (PLD), has encouragedus to try this novel deposition technique in the growth of multilayered heteroepitaxial ferrimagneticiron garnet thin films.Superlattice heterostructures consisting of alternating single crystalline ferrimagnetic yttrium-iron-garnet (YIG) and bismuth-iron-garnet (BIG) thin film layers, as well as alternating YIG and europiumsubstituted BIG (EBIG), were deposited on single crystalline (111) paramagnetic gadolinium-galliumgarnet (GGG) substrates.
Energy-filtering Transmission Electron Microscopy in materials and life science
Authors: Reimer L. 
Published: June 2020

Energy-filtering transmission electron microscopy can be realized by an imaging filter lens in thecolumn of a TEM, a post-column electron energy-loss spectrometer or a dedicated STEM. This offers new possibilities in analytical electron microscopy by combining the operation modes of electron-spectroscopic imaging (ESI), electron-spectroscopic diffraction (ESD) and the record of an electron energy-loss spectrum (EELS).ESI can be used in the zero-loss mode to remove all inelastically scattered electrons. Thicker amorphous and crystalline specimens can be observed without chromatic aberration and with a transmissionof 10−3 up to 80(110) and 150(200) μg/cm2 at 80(120) keV, respectively. This results in a condiserable increase of scattering, phase and Bragg contrast, especially for low Z material because the ratio of inelastic-to-elastic cross section increases as 20/Z with decreasing atomic number. In future energy-filtered high-resolution crystal-lattice images will offer us a better comparison with dynamical simulations. Plasmon loss filtering can be applied for a better separation of phases (e.g. precipitates in a matrix), which differ in their plasmon loss by about 1 eV. Owing to intersections of the energy loss spectra, different parts of a specimen can change their contrast when tuning the selected energy window. Structures containing non carbon atoms will beconsiderably increased in a bright field like contrast relative to the carboneous matrix just below the carbon K edge (structure—sensitive imaging).
Atomic-resolution characterization of an SrTiO3 grain boundary in the STEM
Authors: McGibbon M. M. , Browning N. D. , Chisholm M. F. , McGibbon A. J. , Pennycook S. J. , Ravikumar V. , Dravid V. P. 
Published: June 2020

High-resolution Z-contrast imaging in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition across an interface can be interpreted intuitively without the need for preconcieved atomic structure models. Since the Z-contrast image is formed by electrons scattered through high angles, parallel detection electron energy loss spectroscopy (PEELS) can be used simultaneously to provide complementary chemical information on an atomic scale. The fine structure in the PEEL spectra can be used to investigate the local electronic structure and the nature of the bonding across the interface. In this paper we use the complimentary techniques of high resolution Z-contrast imaging and PEELS to investigate the atomic structure and chemistry of a 25 degree symmetric tilt boundary in a bicrystal of the electroceramic SrTiO3.Figure 1(a) shows a Z-contrast image of a symmetric region of the tilt boundary. The brightest spots in the image correspond to the increased scattering power of the Sr atomic columns (Z=38) with theless bright spots corresponding to the Ti atomic columns (Z=22). The lighter O atomic columns are notvisible in a Z-contrast image.
Twinning and oxygen ordering in Ba2YCu3O7−x crystals
Authors: Iijima Sumio , Ichihashi Toshinari 
Published: June 2020

Formation of twins in Or-BYCO crystals was studied by transforming them to T-phase by electron beam irradiation in the microscope. It is known that during the transformation the crystals developed twinning (STW), Ortho-II phase (1×2 superstructure), tweed structure. These structures occur in that order by the irradiation and the structural changes are caused by oxygen deficiency and oxygen atoms ordering. This work is aimed at elucidation of oxygen atom ordering by examining the structural evolution in terms of morphologies of the twins.Atypical evolution of an Or-BYCO crystal is shown in a series of micrographs in Figs. 1 to 5. As-grown twin (FTW) boundaries have a characteristic lens shape extending in the < 110> direction and terminate at a twin boundary in horizontal direction (Fig.1). These boundaries don't accompany strain contrast which is developed in the crystal after a brief irradiation (Fig.2). The strain contrasts, which are differentiated easily from the thickness contrast, appear parallel to the boundaries and change slowly across the boundaries.
TEM study of a laser ablated YBa2Cu3O7−x thin film on MgO substrate
Authors: Traeholt C. 
Published: June 2020

Since the high Tc superconductors were discovered, the most common compounds have been investigated in detail. This work has mainly been done on bulk specimens. Now as the preparation of these high Tc superconductors is well controlled with respect to the common compounds, thin films become of major interest. In order to study the film—substrate interface cross-sectional specimens for TEM have here been prepared and investigated considering the process of image formation.Thin films, about 100 nm thick, were laser ablated onto a single crystal MgO substrate. This was done in an oxygen atmosphere and with a rotating target of stoichiometric YBa2Cu3O7−x. The subsequent X—ray analysis showed what was believed to be an epitaxially grown film, with its c—axis only deviating a few degrees from the substrate normal. The a— and b—axes of the film were oriented parallel to the <100> directions of the substrate, in spite of a lattice mismatch (YBa2Cu3O7−x a = 3.82 Å, b = 3.89 Å, c = 11.68 Å; MgO a = b = c = 4.2 Å).
HRTEM observation of the phase transition from Bi2Sr2CaCu2O8 to Bi2Sr2Ca2Cu3O10
Authors: Wen Shulin , Ernst F. , Jaeger H. , Mader W. , Majewski P. , Marie M. , Petzow G. , Rühle M. 
Published: June 2020

The investigation of the phase transiton from Bi2Sr2CaCu2O8 (2212) to Bi2Sr2Ca2Cu3O10 (2223) in the system of Bi — Sr — Ca — Cu — O is of interest both from a theoretical and a practical point of view. The result from this investigation may probably lead to a successful pure 2223 phase preparation. The preparation of pure 2223 phase with a simple and satisfactory method still remains a problem although many efforts have been made recently to produce a large percentage of 2223 phase.In order to produce pure 2223 phase most efficiently, the investigation of the transition mechanism from the 2212 to the 2223 phase is necessary. Using a JEM4000EX high resolution transmission electron microscope (HRTEM)we observed this phase transition process at atomic level. The following equation describes the phase transition from 2212 to 2223:
The HREM observation of the boundary between YBCO thin film and substrate
Authors: Liu W. , Wang Y. G. , Li L. 
Published: June 2020

It is a very important problem to obtain high critical current density Jc in high critical temperature Tc superconductors. For high Tc thin film superconductors, the Jc value can reach >106 A/cm2 at 77K. We have prepared YBa2Cu3Oy (YBCO) thin films by magnetron sputtering method, the Jc values ranged from 104 -106 A/cm2, the films were deposited both on (100) SrTiO3 and (100) LaAlO3 substrates. It is well known that Jc is closely related to the microstructure of the film, in this paper we report the observation by high resolution electron microscopy of the boundary between film and substrate and analysis the result with relation to the Jc values of the films.The cross sectional specimens of the film and substrate boundary were
prepared by cutting the film-substrate sample into thin slices, then
stick the slices with film surface face to face by epoxy resin.
Recent progress in the Electron Microscopic studies of Sb and Pb doped Bi-Sr-Ca-Cu-O system
Authors: Fan Chenggao , Yang Li , Xu Qinlun , Cheng Tingzhu , Zhou Guien , Wang Xueqin , Zhang Yuheng 
Published: June 2020

Since 132K superconductivity in Sb and Pb doped Bi-Sr-Ca-Cu-O system was discovered by H.B.Liu et al, the experimental phenomenon has been repeated by many research groups in the world. It is well known that there always coexist several phases in such superconductors. Researchers in our university have attempted to find out which phase takes the responsibility for the high Tc transition by using different preparation methods, varying mixture ratio, changing heat treatment condition. In this contribution,some recent progress in the studies of Sb and Pb doped Bi-Sr-Ca-Cu-O system by electron microscope is presented.An unknown phase is always observed in the Sb and Pb doped Bi-Sr-Ca-Cu-O system.TEM images show that fractures of the phase are quite thick,but they can give sharp electron diffraction patterns accompanying with Laue Zone,and they contain little Cu and Pb which are hardly detectable by EDS. A nearly pure 110K phase specimen was prepared by Qinlun Xu et al, using codeposition of coprecipitated oxalats technique, Only two kinds of fractures have been observed in this sample by TEM, One appeared thin,another thick and small.It was difficult to take series electron diffraction patterns of the latter one, which had been proved to belong to the unknown phase. Considering the preparation condition,the presence of Sb and Pb served to enhance the formation of 80K phase to 110K phase.
In-situ observation of superstructure transformation in Gd2CuO4crystals at elevated temperatures
Authors: Chen C. H. , Cheong S-W. , Werder D. J. 
Published: June 2020

Recently, a commensurate superlattice modulation characterized by a wave vector of= (l/4, l/4, 0) was observed in both pure Nd2CuO4and electron-doped Nd2CuO4−xFx/Nd2−xCexCuO4compounds. The orthorhombic superlattice phase was found to exist in four possible variants with its c-axis parallel to the four equivalent zone-axes of the underlying tetragonal lattice. The origin of this modulation which is commonly observed in the beginning members of the rare-earth-based T' —214 compounds is not yet known. Gd2CuO4which represents the end member to this series has shown to exhibit anomalous magnetic properties.The present study was undertaken to investigate the superstructure in Gd2CuO4single crystals.Thin plate-like crystals of Gd2CuO4were grown from PbO- and CuO-based flux. TEM samples were prepared by ion-milling with a liquid-nitrogen-cooled sample holder.In-situheating experiments were carried out in a JEOL 2000FX electron microscope equipped with a Gatan hot stage.
Structure of carbon in SCS-6 fibers
Authors: Ning X. J. , Pirouz P. 
Published: June 2020

SCS-6 is a high strength (≈3950 MPa), high tensile modulus (≈400 GPa), low density (≈3050 kg/m3) commercial SiC fiber which is of considerable interest as a reinforcement in metal- and ceramic-matrix composites. The microstructure of this fiber has been recently studied in detail by TEM. The fiber microstructure is complicated and consists of an inner coating of carbon and four distinct layers of SiC all deposited on a carbon filament by CVD. In the coated SCS-6 fibers, three sub-layers of carbon, with a total thickness of ≈3μm, containing different densities of SiC particulates, cover the outermost SiC layer. In this paper, the microstructure of the carbon core (filament), the inner carbon coating and the outermost carbon sub-layers are discussed.Cross-sectional TEM specimens were prepared from as-received SCS-6 fibers. Fig. 1 shows a SEM micrograph of the fiber which has a total thickness of 142 μm. A high resolution electron micrograph (HREM) and an electron diffraction pattern (EDP) of the carbon core - of diameter 33 μm - is shown in Fig. 2. Both the HREM micrograph and the EDP are consistent with an assembly of Basic Structure Units (BSUs). A BSU is a small block of parallel graphitic planes stacked in a random manner about a common (c-) axis. The bonding in each plane is of the strong sp type which contrasts with the weak Van der Waals bonding between the planes.
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.
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.