Recent applications of TEM to the study of interfaces

1990 ◽  
Vol 48 (4) ◽  
pp. 308-309
Author(s):  
C. Barry Carter
Keyword(s):  
High Resolution ◽  
Sample Preparation ◽  
Grain Boundaries ◽  
Diffuse Scattering ◽  
Imaging Techniques ◽  
Amorphous Material ◽  
Contrast Imaging ◽  
Current State ◽  
Actual Nature ◽  
High Resolution Images

This paper will review the current state of understanding of interface structure and highlight some of the future needs and problems which must be overcome. The study of this subject can be separated into three different topics: 1) the fundamental electron microscopy aspects, 2) material-specific features of the study and 3) the characteristics of the particular interfaces. The two topics which are relevant to most studies are the choice of imaging techniques and sample preparation. The techniques used to study interfaces in the TEM include high-resolution imaging, conventional diffraction-contrast imaging, and phase-contrast imaging (Fresnel fringe images, diffuse scattering). The material studied affects not only the characteristics of the interfaces (through changes in bonding, etc.) but also the method used for sample preparation which may in turn have a significant affect on the resulting image. Finally, the actual nature and geometry of the interface must be considered. For example, it has become increasingly clear that the plane of the interface is particularly important whenever at least one of the adjoining grains is crystalline.A particularly productive approach to the study of interfaces is to combine different imaging techniques as illustrated in the study of grain boundaries in alumina. In this case, the conventional imaging approach showed that most grain boundaries in ion-thinned samples are grooved at the grain boundary although the extent of this grooving clearly depends on the crystallography of the surface. The use of diffuse scattering (from amorphous regions) gives invaluable information here since it can be used to confirm directly that surface grooving does occur and that the grooves can fill with amorphous material during sample preparation (see Fig. 1). Extensive use of image simulation has shown that, although information concerning the interface can be obtained from Fresnel-fringe images, the introduction of artifacts through sample preparation cannot be lightly ignored. The Fresnel-fringe simulation has been carried out using a commercial multislice program (TEMPAS) which was intended for simulation of high-resolution images.

scholarly journals Simulation and Processing of High Resolution Images of Defects and Interfaces in Superconducting YBa2Cu3O7

1987 ◽  
Vol 99 ◽  
Author(s):  
H. W. Zandbergen ◽  
R. Gronsky ◽  
K. Wang ◽  
G. Thomas
Keyword(s):  
High Resolution ◽  
Grain Boundaries ◽  
Phase Contrast ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Phase Contrast Imaging ◽  
Contrast Imaging ◽  
Resolution Electron ◽  
High Resolution Images

The superconducting performance, in particular the critical current, of polycrystalline YBa2Cu3O7 will depend strongly on the structure of grain boundaries and the nature and number of defects in the microstructure. To characterize the atomic structure of defects and grain boundaries in these materials, a high resolution electron microscopy study has been initiated. Emphasis has been placed on the technique of phase contrast imaging with corresponding computer simulation and processing for optimum interpretation of results.

High-resolution imaging of Σ=5 tilt boundaries in gold

1988 ◽  
Vol 46 ◽  
pp. 590-591
Author(s):  
F. Cosandey ◽  
S.-W. Chan ◽  
P. Stadelmann
Keyword(s):  
High Resolution ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Computational Models ◽  
Spherical Aberration ◽  
Computational Techniques ◽  
Recent Developments ◽  
Tilt Boundaries ◽  
High Resolution Images ◽  
Resolution Imaging

Until recently most of the information concerning the atomic structure of grain boundaries in metals has been obtained using molecular static and molecular dynamic computational techniques. With the recent developments of intermediate voltage microscope (300-400KV) this situation has changed and grain boundary atomic resolution is now possible for most metals. The purpose of this research is to examine the atomic structure of Σ=5 tilt boundaries in Au by high resolution microscopy and to compare the results to computational models.Thin film Au bicrystals containing Σ=5 (θ=36.5°±0.5) tilt grain boundaries were produced by epitaxial growth on NaCl bicrystalline substrates using a technique described in detail elsewhere. All high resolution images were obtained with a Philips 430 ST microscope using axial illumination and without objective aperture. All image simulations were obtained using the multislice formalism with EMS programs. All four {200} reflections from each crystal were used for the simulations with the following instrumental parameters; accelerating voltage V=300KV, spherical aberration constant Cs=1.1mm, defocus spread Δ=8nm and semi-angle beam divergence α=8mrad.

The Study of Grain Boundaries in Ceramics by Electron Diffraction

1980 ◽  
Vol 38 ◽  
pp. 370-373
Author(s):  
C.B. Carter
Keyword(s):  
Grain Boundaries ◽  
Imaging Techniques ◽  
Amorphous Material ◽  
Ceramic Materials ◽  
Boundary Region ◽  
Dark Field ◽  
Intimate Contact ◽  
Diffraction Contrast ◽  
Weak Beam ◽  
Lattice Fringe

Grain boundaries are particularly important in polycrystalline ceramics since it is found experimentally that the properties of the grain boundary region control many properties of the material. In ceramic materials, most interfaces between adjacent grains appear to take one of two forms: they can have a periodic structure if the two grains are in intimate contact - such boundaries would be similar to boundaries observed in metals; or there may be a film of amorphous material present in the interface - the width of such a film may be as little as ~lnm. it is also possible that a second crystalline phase is present at the boundary or, of course, the structure of the interface may consist of a combination of these. Until recently the main techniques used for studying grain boundaries in ceramics have been the strong-beam bright-field and weak-beam dark-field modes of diffraction contrast and lattice-fringe imaging techniques. Diffraction contrast techniques are particularly valuable for studying grain boundaries composed of dislocations where the dislocation spacing is greater than ~15nm or ~4nm for strong-beam and weak-beam respectively. The lattice-fringe imaging technique has been particularly valuable for the identification of boundaries which contain thin films of amorphous material. An additional technique using diffuse scattered electrons to study such boundaries has been shown to be susceptible to misinterpretation when the specimen is coated to prevent charging in the microscope.

Hrem on Grain Boundaries in Oxide Superconductors

1989 ◽  
Vol 156 ◽  
Author(s):  
H.W. Zandbergenl ◽  
G. van Tendeloo
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Amorphous Material ◽  
High Resolution Electron Microscopy ◽  
Critical Currents ◽  
Polycrystalline Materials ◽  
Oxide Superconductors ◽  
Resolution Electron ◽  
Superconducting Oxides

ABSTRACTHigh resolution electron microscopy has been carried out on grain boundaries in a number of superconducting oxides: YBa2Cu3O77−∂, LaCaBaCu3O7−∂, Bi2Sr2CanCun+1O2n+6+∂, and Pb2(Sr, Ca)3−xAxCu2+nO6+2n+∂. In general no amorphous material or another phase is observed at the grain boundaries. It is argued that the low critical currents in these polycrystalline materials are caused by the atomic structure of (001) interfaces at grain boundaries and concerning YBa2Cu3O7 and LaCaBaCu3O7−∂ by the intercalation of CuO layers starting from the grain boundaries.

Z-Contrast Imaging of Grain-Boundary Core Structures in Semiconductors

MRS Bulletin ◽  
1997 ◽  
Vol 22 (8) ◽  
pp. 53-57 ◽  
Author(s):  
M.F. Chisholm ◽  
S.J. Pennycook
Keyword(s):  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Phase Contrast ◽  
Atomic Scale ◽  
Resolving Power ◽  
Boundary Structure ◽  
Contrast Imaging ◽  
Contrast Technique ◽  
Z Contrast

Interest in semiconductor grain boundaries relates to the development of polycrystalline materials for photovoltaics and integrated-circuit interconnects. Although these structures are responsible for deleterious electrical effects, there are few experimental techniques available to study them at the required atomic scale. Therefore models of the physical processes occurring at grain boundaries have necessarily taken a macroscopic approach. Fortunately recent developments have resulted in tools that provide unprecedented glimpses into these interfaces and that will allow us to address anew the connection between grain-boundary structure and properties.Z-Contrast ImagingWhen exploring the unknown, we rely heavily on our eyes (incoherent imaging) to provide a direct image of a new object. In order to explore the unforeseen atomic configurations present at extended defects in materials, it again would be desirable if one could obtain a directly interpretable image of the unfamiliar structures present in the defect cores. Z-contrast electron microscopy provides such a view with both atomic resolution and compositional sensitivity.This high-resolution imaging technique differs from conventional high-resolution phase-contrast imaging. The phase-contrast technique produces a coherent image, an interference pattern formed by recombining the waves diffracted by the specimen. In the Z-contrast technique, the image is incoherent; it is essentially a map of the scattering power of the specimen. Additionally as was first determined by Lord Rayleigh, the incoherent mode of image formation has double the resolving power of the coherent mode.

scholarly journals Biophotonics Modalities for High-Resolution Imaging of Microcirculatory Tissue Beds Using Endogenous Contrast: A Review on Present Scenario and Prospects

2011 ◽  
Vol 2011 ◽  
pp. 1-20 ◽  
Author(s):  
Hrebesh M. Subhash
Keyword(s):  
High Resolution ◽  
Optical Imaging ◽  
Perfusion Imaging ◽  
Imaging Techniques ◽  
Laser Speckle ◽  
Contrast Imaging ◽  
Endogenous Contrast ◽  
Contrast Mechanism ◽  
Recent Developments ◽  
Resolution Imaging

The microcirculation is a complex system, and the visualization of microcirculation has great significance in improving our understanding of pathophysiological processes in various disease conditions, in both clinical and fundamental studies. A range of techniques are available or emerging for investigating different aspect of the microcirculation in animals and humans. This paper reviews the recent developments in the field of high-resolution and high-sensitive optical imaging of microcirculatory tissue beds, emphasizing technologies that utilize the endogenous contrast mechanism. Optical imaging techniques such as intravital microscopy, Capillaroscopy, laser Doppler perfusion imaging, laser speckle perfusion imaging, polarization spectroscopy, photo-acoustic tomography, and various implementations of optical coherence tomography based on Doppler and speckle contrast imaging are presented together with their prospectives and challenges.

High-resolution and diffraction contrast imaging of linear islands formed during molecular beam epitaxy

1995 ◽  
Vol 53 ◽  
pp. 106-107
Author(s):  
D. Loretto ◽  
F. M. Ross ◽  
C. A. Lucas
Keyword(s):  
High Resolution ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Effusion Cell ◽  
Contrast Imaging ◽  
Experimental Conditions ◽  
Plan View ◽  
Diffraction Contrast ◽  
Scientific Curiosity ◽  
High Resolution Images

There is currently a great deal of interest in the growth and properties of 'one-dimensional' structures. This is motivated by scientific curiosity and by the practical urge to fabricate faster, smaller and more efficient electronic and optical devices. It has recently been reported that under certain conditions linear islands can form spontaneously during growth. In this work we investigate linear CaF2 islands which form on Si during molecular beam epitaxy. By combining low resolution diffraction contrast images from plan-view specimens with high resolution images from cross-section specimens we determine that these islands are extremely uniform in width, can be as narrow as 5 nm, and extend over many 10s of μm. We postulate a mechanism for the formation of these novel features based on surface energy minimization.The experimental conditions have been reported in detail elsewhere. Briefly, CaF2 is deposited from an effusion cell onto a Si substrate at 700°C in a vacuum of 1010 Torr.

High-resolution z-contrast imaging of YBa2Cu3O7-δ grain boundaries

1989 ◽  
Vol 47 ◽  
pp. 198-199
Author(s):  
M. F. Chisholm ◽  
S. J. Pennycook
Keyword(s):  
High Resolution ◽  
Grain Boundaries ◽  
Critical Current ◽  
Tilt Angle ◽  
Large Angle ◽  
Boundary Segregation ◽  
Boundary Structure ◽  
Contrast Imaging ◽  
Transmission Electron ◽  
Tilt Boundaries

A rapid reduction of the critical current density across grain boundaries with increasing tilt angle up to ∽10° has been observed in YBa2Cu3O7−δ superconductors. These results fit nicely with an investigation of the structure of low-angle tilt boundaries in these materials. The boundaries are observed to be composed of an asymmetric array of dislocations with a Burgers vector of 1.17 nm for [100] tilt boundaries (Fig. 1) and 0.389 nm for [001] tilt boundaries. It is observed that at 7.5° tilts, the dislocation cores begin to overlap (Fig. 2). Increasing the tilt angle beyond this value is not expected to significantly change the boundary structure which corresponds closely to the point where tilt angle had little further effect on critical current. A complication which was not completely addressed in the study of the structure of these low-angle boundaries is that ceramic materials have a strong tendency to form thin intergranular glass phases and to exhibit enhanced segregation of impurities to the grain boundaries. Conventional transmission electron microscopy and x-ray microanalysis with emitted photons using an energy dispersive spectrometer is of questionable use for this application. A new method for forming high resolution images with strong chemical sensitivity using large-angle elastically scattered electrons in a scanning transmission electron microscope has been used in this study to directly address the grain boundary segregation question.

The Application of High Resolution Chemical Imaging Techniques for Butyl Rubber Blends

2008 ◽  
Vol 81 (2) ◽  
pp. 265-275 ◽  
Author(s):  
Donald A. Winesett ◽  
Andy H. Tsou
Keyword(s):  
High Resolution ◽  
Sample Preparation ◽  
Spatial Resolution ◽  
Secondary Ion Mass Spectrometry ◽  
Imaging Techniques ◽  
Chemical Species ◽  
Chemical Imaging ◽  
Rubber Blends ◽  
Tof Sims ◽  
Good Spatial Resolution

Abstract Atomic Force Microscopy (AFM), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) imaging, and Scanning Transmission X-ray Microscopy (STXM) are applied to identical series of elastomeric blends to evaluate the relative strengths and weaknesses of each imaging technique. AFM is a high resolution, high contrast technique with straight forward sample preparation that derives contrast through elastic modulus variations, but, when used in a conventional mode, has limited chemical specificity. ToF-SIMS imaging can map phases, detect trace levels (ppm) of additives and other chemical species based on relatively straight forward sample preparation, but has poorer spatial resolution and the instrumentation is expensive. STXM has excellent chemical specificity and good spatial resolution but is only available at a beamline and requires more advanced sample preparation. Each technique will be overviewed briefly and relative merits of each will be compared based on evaluations of some commercially relevant rubber blend materials.

scholarly journals FEI Helios NanoLab 400S FIB-SEM

2016 ◽  
Vol 2 ◽  
Author(s):  
Doris Meertens ◽  
Max Kruth ◽  
Karsten Tillmann
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Sample Preparation ◽  
High Performance ◽  
Process Development ◽  
Ion Beam ◽  
High Deposition Rate ◽  
Contrast Imaging ◽  
X Ray ◽  
Sem Imaging

The FEI Helios NanoLab400S FIB-SEM is one of the world's most advanced DualBeamTM focused ion beam (FIB) platforms for transmission electron microscopy (TEM) sample preparation, scanning electron microscopy (SEM) imaging and analysis in semiconductor failure analysis, process development and process control. The FEI Helios NanoLab400S FIB-SEM combines an ElstarTM electron column for high-resolution and high-contrast imaging with a high-performance SidewinderM ion column for fast and precise cross sectioning. The FEI Helios NanoLab M 400S is optimised for high throughput high-resolution S/TEM sample preparation, SEM imaging and energy dispersive X-ray analysis. Its exclusive FlipStageTM and in situ STEM detector can flip from sample preparation to STEM imaging in seconds without breaking vacuum or exposing the sample to the environment. Platinum gas chemistry is the preferred metal deposition when a high deposition rate and precision of the deposition are required. Carbon deposition can be chosen as well. The system additionally allows for spatially resolved compositional analysis using the attached EDAX Genesis XM 4i X-ray microanalysis system.

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