Hrem of Grain Boundaries in Oxides

1986 ◽  
Vol 82 ◽  
Author(s):  
Karl L. Merkle
Keyword(s):  
Grain Boundaries ◽  
Recent Progress ◽  
Atomic Scale ◽  
Resolution Electron ◽  
Ionic Solids ◽  
Electron Microscopes ◽  
Point To Point ◽  
New Generation ◽  
Theory And Experiment ◽  
Better Than

ABSTRACTRecent progress in the understanding of the atomic structure of grain boundaries in ionic solids is briefly reviewed with emphasis on the application of the HREM technique to observations of tilt grain boundaries in NiO. The new generation of high-resolution electron microscopes which are capable of a point-to-point resolution of better than 2 Å have allowed atomic-scale observations that can be directly compared to theoretical grain boundary models. Agreements and differences between theory and experiment are discussed.The importance and significance of faceting and asymmetrical boundaries is pointedout.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

Atomic structure imaging of the Si/SiO2 interface with high-resolution electron microscopy

1986 ◽  
Vol 44 ◽  
pp. 390-391
Author(s):  
J.L. Batstone ◽  
J.M. Gibson ◽  
Alice.E. White ◽  
K.T. Short
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Atomic Structure ◽  
High Resolution Electron Microscopy ◽  
Medium Voltage ◽  
Voltage Electron ◽  
Resolution Electron ◽  
Structural Image ◽  
Electron Microscopes ◽  
Point To Point

High resolution electron microscopy (HREM) is a powerful tool for the determination of interface atomic structure. With the previous generation of HREM's of point-to-point resolution (rpp) >2.5Å, imaging of semiconductors in only <110> directions was possible. Useful imaging of other important zone axes became available with the advent of high voltage, high resolution microscopes with rpp <1.8Å, leading to a study of the NiSi2 interface. More recently, it was shown that images in <100>, <111> and <112> directions are easily obtainable from Si in the new medium voltage electron microscopes. We report here the examination of the important Si/Si02 interface with the use of a JEOL 4000EX HREM with rpp <1.8Å, in a <100> orientation. This represents a true structural image of this interface.

Characterization of Rh/Si multilayer structure by HREM and HAADF

1992 ◽  
Vol 50 (1) ◽  
pp. 122-123
Author(s):  
Y. Cheng ◽  
J. Liu ◽  
M.B. Stearns ◽  
D.G. Steams
Keyword(s):  
Normal Incidence ◽  
High Resolution Electron Microscopy ◽  
X Rays ◽  
Beam Direction ◽  
Cross Sectional ◽  
Optical Elements ◽  
Resolution Electron ◽  
Point To Point ◽  
Better Than

The Rh/Si multilayer (ML) thin films are promising optical elements for soft x-rays since they have a calculated normal incidence reflectivity of ∼60% at a x-ray wavelength of ∼13 nm. However, a reflectivity of only 28% has been attained to date for ML fabricated by dc magnetron sputtering. In order to determine the cause of this degraded reflectivity the microstructure of this ML was examined on cross-sectional specimens with two high-resolution electron microscopy (HREM and HAADF) techniques.Cross-sectional specimens were made from an as-prepared ML sample and from the same ML annealed at 298 °C for 1 and 100 hours. The specimens were imaged using a JEM-4000EX TEM operating at 400 kV with a point-to-point resolution of better than 0.17 nm. The specimens were viewed along Si [110] projection of the substrate, with the (001) Si surface plane parallel to the beam direction.

Limits for high-resolution electron microscopy of inorganic materials?

1987 ◽  
Vol 45 ◽  
pp. 4-5
Author(s):  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
Spherical Aberration ◽  
High Resolution Electron Microscopy ◽  
Inorganic Materials ◽  
Atomic Scale ◽  
Resolution Limit ◽  
Contrast Transfer Function ◽  
Existing Problems ◽  
Resolution Electron ◽  
Electron Microscopes

The era of atomic-resolution electron microscopy has finally arrived. In virtually all inorganic materials, including oxides, metals, semiconductors and ceramics, it is possible to image individual atomic columns in low-index zone-axis projections. A whole host of important materials’ problems involving defects and departures from nonstoichiometry on the atomic scale are waiting to be tackled by the new generation of intermediate voltage (300-400keV) electron microscopes. In this review, some existing problems and limitations associated with imaging inorganic materials are briefly discussed. The more immediate problems encountered with organic and biological materials are considered elsewhere.Microscope resolution. It is less than a decade since the state-of-the-art, commercially available TEM was a 200kV instrument with a spherical aberration coefficient of 1.2mm, and an interpretable resolution limit (ie. first zero crossover of the contrast transfer function) of 2.5A.

The Contribution of Intermediate-Voltage, High-Resolution Electron Microscopy In Materials Science: An Appraisal

1990 ◽  
Vol 48 (1) ◽  
pp. 478-479
Author(s):  
John L. Hutchison
Keyword(s):  
High Resolution ◽  
Materials Science ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
The Past ◽  
Resolution Electron ◽  
Extreme Sensitivity ◽  
Electron Microscopes ◽  
New Generation ◽  
Small Metal Particles

Over the past five years or so the development of a new generation of high resolution electron microscopes operating routinely in the 300-400 kilovolt range has produced a dramatic increase in resolution, to around 1.6 Å for “structure resolution” and approaching 1.2 Å for information limits. With a large number of such instruments now in operation it is timely to assess their impact in the various areas of materials science where they are now being used. Are they falling short of the early expectations? Generally, the manufacturers’ claims regarding resolution are being met, but one unexpected factor which has emerged is the extreme sensitivity of these instruments to both floor-borne and acoustic vibrations. Successful measures to counteract these disturbances may require the use of special anti-vibration blocks, or even simple oil-filled dampers together with springs, with heavy curtaining around the microscope room to reduce noise levels. In assessing performance levels, optical diffraction analysis is becoming the accepted method, with rotational averaging useful for obtaining a good measure of information limits. It is worth noting here that microscope alignment becomes very critical for the highest resolution.In attempting an appraisal of the contributions of intermediate voltage HREMs to materials science we will outline a few of the areas where they are most widely used. These include semiconductors, oxides, and small metal particles, in addition to metals and minerals.

Characterization of Grain Boundaries and Interfaces by High Resolution Transmission Electron Microscopy

1989 ◽  
Vol 153 ◽  
Author(s):  
William Krakow
Keyword(s):  
High Resolution ◽  
Grain Boundaries ◽  
Ohmic Contacts ◽  
Dielectric Material ◽  
Medium Voltage ◽  
Voltage Electron ◽  
Resolution Electron ◽  
Interfacial Structures ◽  
Tilt Boundaries ◽  
Electron Microscopes

AbstractSeveral examples will be given of high resolution electron microscope images of both grain boundaries and interfaces and the methods which have been applied to understanding their atomic structure. Specific expitaxial interfacial structures considered are: Pd2Si/Si used for ohmic contacts, Al on Si overlayers and CaF2/Si where the CaF2, is an attractive possibility as a dielectric material. For the case of grain boundaries specific examples of both twist and tilt boundaries in Au will be given to show the imaging capability with the new generation of medium voltage electron microscopes.

Lattice Imaging of a High-Angle Grain Boundary in Germanium at 500kv

1977 ◽  
Vol 35 ◽  
pp. 108-109
Author(s):  
O.L. Krivanek ◽  
S. Isoda ◽  
K. Kobayashi
Keyword(s):  
Phase Contrast ◽  
Room Temperature ◽  
Materials Science ◽  
High Angle ◽  
Lattice Imaging ◽  
Imaging Parameters ◽  
Resolution Electron ◽  
Electron Microscopes ◽  
New Generation ◽  
Transfer Interval

The promise of the new generation of high-voltage, high-resolution electron microscopes (HREMs) for atomic resolution studies in materials science has excited considerable interest (1). This paper describes an application to elemental Ge of the first member of this generation, the Kyoto 500kV HREM (2).Fig. 1 shows a (Oil) Ge crystal almost certainly less than 100Å thick, supported by a thin amorphous Ge film and surrounded by several Au crystallites. The specimen was prepared by vapor co-deposition of Au and Ge from separate sources onto a rock salt substrate held at room temperature. The imaging parameters were: accelerating voltage 500kV, axial illumination, no objective aperture, el. opt. mag. 200 000x, exposureotime 10 secs and, as the optical diffractogram (Fig. lb) shows, defocus =-600Å (≃ Scherzer defocus). The dashed circles in the diffractogram show the theoretical extent of the first phase-contrast transfer interval. The interval easily includes all the 111 diffraction spots, indicating that all the end-on (ill) planes and the defects they contain have been imaged faithfully and without distortion.

High-resolution imaging of symmetric tilt and mixed character boundaries in Al

1990 ◽  
Vol 48 (4) ◽  
pp. 336-337
Author(s):  
M. Shamzuzzoha ◽  
P.A. Deymier ◽  
David J. Smith
Keyword(s):  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Thin Foil ◽  
Polycrystalline Materials ◽  
Voltage Electron ◽  
Symmetric Tilt ◽  
Resolution Electron ◽  
Resolution Imaging ◽  
Electron Microscopes

The determination of the core structure of grain boundaries is central to a better understanding of the properties of polycrystalline materials. With the recent advent of intermediate-voltage electron microscopes (300-400kV), it is possible to obtain atomic-resolution images of grain boundaries in many metals - for example, the atomic structure of periodic grain boundaries in selected metals has been studied. Our knowledge of materials properties can be further enhanced by investigating more complex, arbitrarily misoriented grain boundaries. In this paper, we will report HREM imaging of a symmetric tilt low-angle grain boundary and a twist-and-tilt (mixed character) grain boundary in Al.The Al bicrystals used in this study were produced by cross-rolling and annealing methods described in detail elsewhere. Thin foil specimens of 3mm diameter containing specific boundaries were obtained by spark-cutting and subsequent electropolishing in 73% methanol, 25% nitric acid and 2% hydrochloric acid. HREM was performed with a JEM-4000EX operated at 400kV, using axial illumination and without an objective aperture. High-resolution electron micrographs were recorded near the optimum defocus, typically at a magnification of 500,000 times.

Research thrusts and the BRITE-EURAM project

1991 ◽  
Vol 49 ◽  
pp. 448-449
Author(s):  
D. Van Dyck
Keyword(s):  
High Resolution ◽  
Amorphous Materials ◽  
High Resolution Electron Microscopy ◽  
Reliable Information ◽  
Atomic Scale ◽  
Trial And Error ◽  
Resolution Electron ◽  
Structural Details ◽  
Electron Microscopes ◽  
The Individual

The most performant high resolution electron microscopes nowadays achieve a resolution of about 0.2 nm so that the structural details of matter can be visualised at the atomic scale.If a resolution of 0.1 nm could be reached, most of the individual atoms of a structure could be resolved which would make high resolution electron microscopy (HREM) an extremely and unparalleled technique for the study of materials, especially for the characterisation of the structure of defects, new materials, crystalline as well as disordered and amorphous, etc. However, the potential power of the technique is still severely limited by the problem of the interpretation of the images. Thus far, the only way to obtain reliable information is by comparing simultaneously the experimental images with computer calculated images for various structure models. However, this trial and error technique requires a large amount of prior information obtained by other techniques and makes HREM much more dependent and thus much less powerful. For complicated structures such as defects, disordered and amorphous materials, hardly no reliable information can be obtained at present.

Quantification of grain boundary parameters using high-resolution Electron Microscopy

1994 ◽  
Vol 52 ◽  
pp. 912-913
Author(s):  
M. I. Buckett ◽  
K. L. Merkle
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Volume Expansion ◽  
Boundary Energy ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Lattice Fringe ◽  
Resolution Electron ◽  
Point To Point

With the advances in instrumentation and the capability of point-to-point resolution better than 0.2 nm, high resolution electron microscopy (HREM) is becoming more widely used for the quantitative study of both surfaces and internal interfaces. The elegance of the technique lies in its ability to deduce atomic-scale information on a localized scale. Without the proper analysis, however, HREM images can easily be misinterpreted. We investigate the considerations necessary for quantification of HREM images, using the measurement of the grain boundary volume expansion via the lattice fringe displacement technique as an example. The volume expansion, a parameter directly related to the grain boundary energy, is measured (in length units on the order of tenths of Å) as a rigid body translation normal to the boundary. It can be determined experimentally using statistical techniques which locate and fit the peak and valley positions in an experimental HREM image such that a direct measurement of the lattice fringe displacements is made.

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