bluuebunny/crossref_metadata_2025_split huggingface dataset:
Near-field optical microscopy/spectroscopy of discrete quantum emitters
Authors: Betzig E. 
Published: June 2020

A subwavelength sized source or detector of visible light can be raster scanned in close proximity to the surface of a sample to generate images at a resolution well beyond the classical diffractional limit. Applications of the resultant technique, near-field scanning optical microscopy (NSOM), include fluorescence imaging of fixed cells, mode profiling of semiconductor lasers, and high density magnetooptic data storage. The focus of this presentation, however, will be on the more recent use of NSOM in the identification and characterization of discrete quantum emitters from within an ensemble.Two such systems will be discussed. The first involves the detection and characterization of single fluorescent molecules. The usual difficulty with single molecule detection is not the inherently weak luminescence signal from each molecule, but rather the large background from impurity luminescence and Raman scattering within the excitation volume. NSOM greatly reduces this volume and hence the resultant background, yielding sensitivity of 0.005 molecules.
Displacement at the twin boundary in YBa2Cu3O7 superconductor
Authors: Zhu Yimei , Pan M. , Li Z.G. , Suenaga M. , Welch D. 
Published: June 2020

A shear displacement at the twin boundary in YBa2Cu3O7 superconductor has been observed by means of High Resolution Electron Microscopy. It was found that the a and b planes across the twin boundary are shifted along the boundary by a distance of (1/3 ∼ 1/2) · 2d110. In order to confirm our observation and give an optimum interpretation of the HREM image, computer simulation of the twin structure in YBa2Cu3O7 was carried out.A large supercell, 81.72×21.72×11.70 Å, with a total of 1492 atoms was constructed to simulate the twin structure. The twin boundary is modeled not only by a rotation of the planes in one domain with respect to the adjacent domain by an angle of 90° - ϕ (ϕ≈0.967°) but also by a translation (R= 1/3•2d110) along the boundary. In addition, in order to simulate the diffused boundary, boundary steps in and directions as shown in Fig.1(d) were introduced.
HRTEM analysis on phase transitions in Bi-based superconductive oxides
Authors: Horiuchi S. , Shoda K. , Wu X.J. , Nozaki H. , Tsutsumi M. , Matsui Y. 
Published: June 2020

It is known for the superconductors in a Bi-Sr-Ca-Cu-O system that there are three phases. Bi2Sr2CuOx, Bi2Sr2CaCu2Ox and Bi2Sr2Ca2Cu3Ox, which are called for simplicity the (2201), (2212) and (2223) phases with the critical temperatures Tc at about 20, 85 and 110K respectively. Their crystal structures are closely related and the phase transition among them often occurs. When the specimen in the partially molten state was quenched to ice-water, it was composed of a Bi-rich, amorphous phase and impurity phases like Ca1−zSrzCuO2. On crystallization the former became the (2201) phase. On further heating at higher temperature firstly the (2212) phase and secondly the (2223) phase were obtained.In the present study the structural variation during the transition from the (2201) phase to the (2212) phase and further to the (2223) phase was clarified mainly by using a high-resolution transmission electron microscopy (IIRTEM). Thin specimens were prepared by ion-thinning method and observed by a 200kV TEM (JEM 2000EX). The mechanism of the phase transition was discussed from the structural viewpoint.
Origin of superstructure modulations in Bi-Sr-Ca-Cu-O superconductors
Authors: Gai Pratibha L. , Subramanian M.A. , Sleight Arthur W. 
Published: June 2020

New insights into the origin of superstructure modulations in Bi-Sr-Ca-Cu-O superconductors with the idealized formulation Bi2Sr2CaCu2O8 (2212) have been obtained primarily from electron microscopy. Systematic investigations of the Bi-Sr-Ca-Cu-O samples annealed in both reducing and oxidizing environments show that the superconducting transition temperature (Tc) decreases for the oxygen-annealed samples containing oxygen interstitials. Electron diffraction has revealed significant local differences in the modulation periodicities depending on the annealing environment. Superstructure modulations have also been found in the samples prepared entirely in reducing nitrogen. Rare-earth doped Bi2Sr2Ca1−xYxOy have also been examined in different environments. High precision microanalysis using quantitative EDX shows that the modulations are insensitive to the concentration of cation point defects.Proposed models for superstructure modulations include: a rigid rotation of CuO5 polyhedra which may result from small differences in the equilibrium bond lengths between Bi-O and Cu-O layers; ordering of Bi-concentrated and deficient zones;
The role of specimen morphology in the preparation of High-TC superconductors for Transmission Electron Microscopy
Authors: Powers M. 
Published: June 2020

It is vital in TEM investigations, especially for high resolution studies, that specimen quality be optimized and the information desired in a particular TEM analysis often prescribes the method of specimen preparation required. We have found that the morphology of a bulk superconductor sample can significantly influence the ultimate success of the preparation technique utilized.Methods employed for the production of electron transparent foils of ceramic oxide superconductors include mechanical grinding, cleavage, jet polishing, ultramicrotomy and ion milling. Grinding and cleavage are both low cost, quick and easy specimen preparation techniques. However, because of the layered crystal structures of these materials, they display a marked tendency to cleave along (001) planes, and hence the range of crystallographic orientations available with these methods is restricted. With grinding in particular, mechanical deformation can be a problem while with cleavage, transparent areas are confined to the vicinity of particle edges.
Correlation of electrical properties of Bi-Sr-Ca-Cu-O superconductor with changes in microstructure and composition caused by rapid heating and cooling
Authors: Duan Q. , Dash J. 
Published: June 2020

Samples of Bi2Sr2CaCu2Ox were prepared from a mixture of reagent-grade Bi2O3, SrCo3, CaCo3, and CuO. After mixing and grinding, the powder was sintered for 24 h at 800 C. Then the sinter was again ground and then pressed into pellets about 12.5 mm dia.The pellets were heated at 880 C in air for 20 h and then quenched rapidly in liquid nitrogen. In this condition the surface had a granular structure, as shown by the SEM image, Fig. 1. The average surface composition of this area is indicated by the EDS spectrum, Fig. 2.The pellets were then exposed to pure argon at about 1000 C and 1000atm pressure in a ballistic compressor. The time of exposure to hot, dense argon was about 10−3 sec. The samples were then cooled at a rate of about 105 C per second. After this treatment, the granular surface texture was completely gone, Fig. 3.
Xenon ion irradiation of superconducting YBa2Cu3O7 thin films
Authors: Watanabe H. , Kabius B. , Roas B. , Urban K. 
Published: June 2020

Recently it was reported that the critical current density(Jc) of YBa2Cu2O7, in the presence of magnetic field, is enhanced by ion irradiation. The enhancement is thought to be due to the pinning of the magnetic flux lines by radiation-induced defects or by structural disorder. The aim of the present study was to understand the fundamental mechanisms of the defect formation in association with the pinning effect in YBa2Cu3O7 by means of high-resolution electron microscopy(HRTEM).The YBa2Cu3O7 specimens were prepared by laser ablation in an insitu process. During deposition, a substrate temperature and oxygen atmosphere were kept at about 1073 K and 0.4 mbar, respectively. In this way high quality epitaxially films can be obtained with the caxis parallel to the <100 > SrTiO3 substrate normal. The specimens were irradiated at a temperature of 77 K with 173 MeV Xe ions up to a dose of 3.0 × 1016 m−2.
A model for the modulation in Bi2−xPbxSr2CaCu2O8+δ with large x
Authors: Zandbergen H. W. , van Tendeloo G. 
Published: June 2020

Compounds with composition Bi2−xPbxSr2CaCu2O8+∂ show to have two different kinds of incommensurate superstructures. The first one (Bi-type) occurs for x being small and for the pure Bi compound. This superstructure is reported by many authors, which all reports shifts of all atoms. The modulation is directed along the b axis and the modulation vector was found to vary between about 3.5b and 5.0b for Ca completely replaced by Y and Bi2−xPbxSr2CaCu2O8+∂ with x being 0.1 respectively. A model for the modulation was proposed by Zandbergen et al, based on the interpretation of HREM images and structural chemistry arguments. This model, assuming the introduction of extra oxygen in the BiO layers to decrease the mismatch between the BiO layers and the perovskite blocks with which the BiO layers are sandwiched, has been proven to be basically right and is schematically represented in Figure 1.For x being larger than about 0.2 the amplitude of the Bi type of modulation starts to decrease and another type of modulation (Pb-type) is occurring. A number of authors have reported this type of of modulation but up till now no explanation has been given. The modulation vector is mostly reported to be close to 7.5b but also a variation with x is reported. When x is between 0.2 and 0.5 both types of modulation are present and Pierre et al report that when both modulation are present the ratio of both modulation vectors is 3/2. Similarly to the Bi type of modulation, the Pb type of modulation is accompanied with a periodicity of 0.54 nm along the a axis, as is shown in Figure 2.
Structures and crystallization of vacuum-deposited amorphous Se and Sb films
Authors: Shiojiri Makoto , Isshiki Toshiyuki , Fudaba Tetsuya , Hirota Yoshihiro 
Published: June 2020

In hexagonal Se crystal each atom is covalently bound to two others to form an endless spiral chain, and in Sb crystal each atom to three others to form an extended puckered sheet. Such chains and sheets may be regarded as one- and two- dimensional molecules, respectively. In this paper we investigate the structures in amorphous state of these elements and the crystallization.HRTEM and ED images of vacuum-deposited amorphous Se and Sb films were taken with a JEM-200CX electron microscope (Cs=1.2 mm). The structure models of amorphous films were constructed on a computer by Monte Carlo method. Generated atoms were subsequently deposited on a space of 2 nm×2 nm as they fulfiled the binding condition, to form a film 5 nm thick (Fig. 1a-1c). An improvement on a previous computer program has been made as to realize the actual film formation. Radial distribution fuction (RDF) curves, ED intensities and HRTEM images for the constructed structure models were calculated, and compared with the observed ones.
TEM study of amorphization of Cu and Ti foils by cold-rolling
Authors: Chiou W. A. , Jeon N. L. , Xu Genbao , Meshii M. 
Published: June 2020

For many years amorphous metallic alloys have been prepared by rapid quenching techniques such as vapor condensation or melt quenching. Recently, solid-state reactions have shown to be an alternative for synthesizing amorphous metallic alloys. While solid-state amorphization by ball milling and high energy particle irradiation have been investigated extensively, the growth of amorphous phase by cold-rolling has been limited. This paper presents a morphological and structural study of amorphization of Cu and Ti foils by rolling.Samples of high purity Cu (99.999%) and Ti (99.99%) foils with a thickness of 0.025 mm were used as starting materials. These thin foils were cut to 5 cm (w) × 10 cm (1), and the surface was cleaned with acetone. A total of twenty alternatively stacked Cu and Ti foils were then rolled. Composite layers following each rolling pass were cleaned with acetone, cut into half and stacked together, and then rolled again.
Formation process of periodic non-conservative antiphase boundary structure in L-Pd5Ce
Authors: Itakura Masaru , Kuwano Noriyuki , Oki Kensuke 
Published: June 2020

The low temperature phase of Pd5Ce (L-Pd5Ce) has a one-dimensional long period superstructure (1D-LPS) derived from Ll2. The periodic antiphase boundaries (APBs) are parallel to (110) planes and have a shift vector of 1/2[110]. Hereafter, the indices are referred to the basic lattices of Ll2 As insertion of the APB causes a change in composition, such an APB is called “non-conservative”. Then, a domain size M depends upon the Ce concentration in the alloy. It was found that M increases also with temperature. The temperature dependency of M is attributed to a change of the degree of order within the antiphase domains. In this work, morphology of the non-conservative APBs is observed to clarify the formation process of the 1D-LPS.The alloy of Pd-16.7 at%Ce was prepared by arc melting in argon atmosphere. Disc specimens made from the alloy ingot were first held at 985 K for 260 ks and quenched in iced water to obtain the state of M=∞ or Ll2, followed by annealing for various lengths of time. The annealing temperature was 873 K where the equilibrium value for M is about 3 in unit of (110) lattice spacing of Ll2. Observation was carried out using microscopes JEM-2000FX, JEM-4000EX (HVEM Lab., Kyushu Univ.) and JEM-2000EX (Dept. of Mater. Sci. Tech., Kyushu Univ.).
Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4
Authors: Yamamoto Naoki , Kikuchi Makoto , Atake Tooru , Hamano Akihiro , Saito Yasutoshi 
Published: June 2020

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.
HREM observation of stacking faults in Guinier-Preston zones for Al-Ag alloys
Authors: Schwander P. , Dubey Ph.A. , Kostorz G. 
Published: June 2020

The decomposition of Al-rich Al-Ag-alloys quenched from the solid solution (α) and aged within the metastable miscibility gap, follows the sequence GP zones → γ' → γ (Ag2Al). Nearly spherical GP zones (Guinier-Preston zones) coherent with the fee matrix are formed by homogeneous nucleation and growth, whereas γ' plate-like precipitates with an hdp structure — lying on {111}-planes of the fee matrix — nucleate heterogeneously at dislocations after a certain incubation time. In the present work HREM was used to investigate the internal structure of the GP zones.Single crystals of Al-3 at.% Ag grown by strain-annealing were cut along (110) by spark erosion. The samples were homogenized for 2 h at 580°C prior to ageing for 43 h at 160°C. They were electrolytically thinned at −30°C in a methanol-HNO3 (2:1) solution. The TEM work was performed on a Philips CM 30 fitted with a Super Twin Lens and a double tilt holder. To bring the electron beam parallel to the optical axis the coma-free alignment was used. At 300 kV the instrumental point resolution was determined to be 1.9 Å using the Young’s fringes method.
Understanding complex phase chemistry in a Ni-base superalloy: A combined AEM/APFIM approach
Authors: Burke M.G. , Miller M.K. 
Published: June 2020

Alloy 718 is a Nb-modified Ni-base superalloy widely-used for gas turbine and related applications which require microstructural stability and good mechanical properties at elevated temperatures (≈ 650°C). In order to achieve the desired properties, the alloy is given a multi-step thermal treatment during which a complex multiphase microstructure is developed. The primary strengthening phases in this alloy are DO22-ordered γ" and Ll2-ordered γ'. A variety of other phases such as Laves, MC-type carbides, and δ (Ni3Nb) have been observed in this material. In this study, the techniques of analytical electron microscopy (AEM) and atom probe field-ion microscopy (APFIM) have been successfully applied to characterize the microstructure of Alloy 718.The nominal bulk composition of the material examined in this investigation is listed in Table 1 together with the heat treatment schedule. Specimens for AEM characterization were examined in a Philips EM400T analytical electron microscope operated at 120kV and equipped with a Link LZ5/AN10-85S analyzer system.
Fractal formation in Al/Ge bilayer films after annealing
Authors: Wu Zi-Qin , Zheng Bin 
Published: June 2020

The temperature of crystallization of amorphous semiconductor films contacted with metal film is much lower than that of isolated amorphous films. This phenomenon is called metal-enhanced crystallization. In our previous works many fractals were formed after crystallization in bilayer films Pd/Si, Au/Ge and Ag/Ge. Based on TEM observation a mechanism of random successive nucleation was proposed to simulate the fractal formation in Pd/Si films. In this paper the fractal formation in Al/Ge films with different thickness ratios of Al and Ge is reported.At first Ge and then Al were evaporated onto fresh cloven NaCl in ordinary high vacuum without breaking the vacuum. Thicknesses of Ge and Al were obtained from masses of Ge and Al used according to the formula of point evaporation source as follows:
Use of ultra-microtomy to study phase relationships in industrial alumina particles
Authors: Antonovsky Ari 
Published: June 2020

Production of smelting grade alumina relies on the transformation at high temperature (1200°C) of aluminium hydroxide (Al2(OH)3) to alumina (A12O3). In this process, a number of poly-morphic transformations occur which are related to the thermal conditions experienced by particles as they pass through a calcination furnace. TEM is required to study the effect of these transformations on the internal morphology of industrial alumina particles. The information from this can then be related to performance within the smelting operation. Cross-sections of whole particles (up to 70μm diameter) can only be obtained by ultra-microtomy of resin-embedded alumina.Samples of aluminium hydroxide and alumina were embedded in resin blocks (EPON or L.R. White - Hard Grade). Ultra-thin sections (∽50nM) were cut from the blocks using a MICRO-STAR diamond knife and an LKB IV ultra-microtome. Sections of particles were examined using a TEM to identify the different forms of alumina present, and characterise their relative distribution in a sample.
HREM studies of modulated structures of the monoclinic (B) phase in CaO-Dy2O3 solid solutions
Authors: Kim Y. J. , Kriven W. M. 
Published: June 2020

Dysprosia (Dy203) undergoes a monoclinic (B) to cubic (C) transformation on cooling through 1860°C, which is accompanied by an 8% volume increase and shattering. Minor additions of CaO combined with rapid quenching, however, are able to stabilize the high temperature phase at room temperature, which is incommensurately modulated. TEM studies revealed the existence of three different modulations: q1 (001-type; λ ≈ 9.0 Å), q2 (200-type; λ ≈ 7.5 Å), and q3 (λ ≈ 40 Å). HREM studies on modulated specimens have been conducted to search for the origin of these modulated microstructures.Fig. 1 shows characteristic modulations in the [010]B orientation. Whereas both q1 and q2 look like normal lattice fringes in moderate resolution TEM images, HREM images indicate that they are actually not strictly linear but somewhat displaced. This discontinuity is more obvious in the HREM images displaying separate q1 and q2 modulations such as q1 in the [110] orientation (Fig. 2) and q2 in the [011] orientation (Fig. 3).
The structure of small metal crystallites on cerium dioxide
Authors: Cochrane Heather D. , Hutchison John L. , White Donald 
Published: June 2020

Many important catalyst systems involve small metal particles supported on ceramics. The development of such catalysts requires an understanding of the structures of the particles and their relationship with their supports. There have been several studies of the dynamic behaviour of metal particles on apparently inactive supports, an example being the work by Iijima on gold particles supported on silicon.The high resolution microscopy technique of surface profile imaging has been used to study ceria by itself and various ceria supported metal particles including platinum and gold. Electron Microscopy was carried out using two JEOL 4000EX electron microscopes with 1.67 and 1.6 angstrom resolution respectively. Real and model catalysts were prepared as described elsewhere to produce metal particles up to 4nm in diameter, on well-crystallised ceria.
Comparison of TEM and STM observations of small silver clusters on different carbon supports
Authors: Tesche Bernd , Schilling Tobias 
Published: June 2020

The objective of our work is to determine:a) whether both of the imaging methods (TEM, STM) yield comparable data andb) which method is better suited for a reliable structure analysis of microclusters smaller than 1.5 nm, where a deviation of the bulk structure is expected.The silver was evaporated in a bell-jar system (p 10−5 pa) and deposited onto a 6 nm thick amorphous carbon film and a freshly cleaved highly oriented pyrolytic graphite (HOPG).The average deposited Ag thickness is 0.1 nm, controlled by a quartz crystal microbalance at a deposition rate of 0.02 nm/sec. The high resolution TEM investigations (100 kV) were executed by a hollow-cone illumination (HCI). For the STM investigations a commercial STM was used. With special vibration isolation we achieved a resolution of 0.06 nm (inserted diffraction image in Fig. 1c). The carbon film shows the remarkable reduction in noise by using HCI (Fig. 1a). The HOPG substrate (Fig. 1b), cleaved in sheets thinner than 30 nm for the TEM investigations, shows the typical arrangement of a nearly perfect stacking order and varying degrees of rotational disorder (i.e. artificial single crystals). The STM image (Fig. 1c) demonstrates the high degree of order in HOPG with atomic resolution.
The influence of surface defects on the catalytic reaction of submonolayer films observed by photoemission electron microscopy
Authors: Mundschau M. , Kordesch M. E. , Rausenberger B. , Engel W. , Bradshaw A. M. , Zeitler E. 
Published: June 2020

Defects on surfaces are known to greatly enhance the rate of many catalytic reactions. In some cases, the active sites in catalysis may reside only at defect sites. Surface defects are best characterized by microscopic techniques. It was demonstrated earlier that catalytic reactions can be followed using an ultra high vacuum version of a classical photoemission electron microscope. This technique can image submonolayer coverages because of the extreme sensitivity of photoemission to local work function.We report here studies on the catalytic oxidation of adsorbed CO on Pt which was followed in situ and in real time. For temperatures below 500 K and for partial pressure ratios of oxygen to CO of less than ∽ 10:1, an adsorbed layer of CO forms which effectively blocks the co-adsorption of oxygen.