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.

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.

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.

Surface studies in UHV: Applications of High-resolution electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 444-445
Author(s):  
M. R. McCartney ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Vacuum ◽  
High Resolution Electron Microscopy ◽  
Plan View ◽  
Voltage Electron ◽  
Resolution Electron ◽  
Video Systems ◽  
Electron Microscopes

The examination of surfaces requires not only that they be free of adsorbed layers but the environment of the sample must also be maintained at high vacuum so that the surfaces remain clean. The possibility of resolving surface structures with atomic resolution has provided the motivation for optimizing intermediate and high voltage electron microscopes for this particular application. Electron microscopy offers a variety of techniques which have the capability of achieving atomic level detail of surfaces including plan-view imaging, REM and profile imaging. Operation at higher voltages permits reasonable pole piece dimensions thereby providing space for in situ studies yet still compatible with high resolution. Moreover, video systems can be attached which permit observation and recording of dynamic phenomena without compromising microscope performance.

Recent trends in high-resolution electron microscopy

1986 ◽  
Vol 44 ◽  
pp. 530-533
Author(s):  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Two Dimensional ◽  
Planar Defects ◽  
Medium Voltage ◽  
Resolution Electron ◽  
Routine Basis ◽  
Recent Trends ◽  
Electron Microscopes

The recent advent of high-resolution electron microscopes (HREMs) capable of resolving sub-2-Ångstrom detail on a routine basis has led to an enormous increase in the range of materials which can be usefully studied. Not only is it possible to resolve individual atomic columns in low index zones of most common metals but observations of semiconductors, for example, are no longer restricted to the traditional [110] zone, thereby making it feasible at last to obtain two-dimensional information about surfaces, interfaces and other planar defects. There is a worldwide upsurge of interest in the capabilities of these machines and the so-called medium-voltage (300-400kV) HREMs are selling rapidly despite their considerable expense. Our objective here is to provide a brief and selective overview of the latest applications and likely trends in HREM studies of materials - further details can be found elsewhere in these proceedings. No attempt is made to review instrumentation developments since they are being considered separately.

A New Method of Preparing Tilt Boundaries for High Resolution Electron Microscopy

1987 ◽  
Vol 115 ◽  
Author(s):  
William Krakow ◽  
Victor Castańo
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
High Resolution ◽  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Zone Axis ◽  
New Method ◽  
Lateral Overgrowth ◽  
Resolution Electron ◽  
Tilt Boundaries

ABSTRACTA new method of preparing bicrystal substrates of NaCl with a common tilt zone axis has been developed. Upon a lateral overgrowth of NaCl, bridging the two mechanically polished and oriented crystals, very thin films can then be vapor deposited. Au bicrystals of ∼ 75Å thickness and b.c.c. Cr films of similar thickness with grain boundaries have been fabricated.

High-resolution Electron Microscopy of defects in Ni3Al

1989 ◽  
Vol 47 ◽  
pp. 302-303
Author(s):  
M. J. Mills
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Theoretical Models ◽  
High Resolution Electron Microscopy ◽  
Current Application ◽  
Voltage Electron ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Electron Microscopes ◽  
Anti Phase Boundary

The improved resolution of the latest generation of intermediate voltage electron microscopes makes possible the direct study of the atomic structure of defects in close-packed metals and alloys. Of particular technological interest are several classes of intermetallic compounds which exhibit desirable mechanical properties at higher temperatures. This paper demonstrates the current application of high resolution transmission electron microscopy (HRTEM) to the study of dislocation cores and interfaces in nickel-based alloys, and the implications of the observations in terms of models of deformation and fracture.Several intermetallic alloys with the L12 (Cu3Au) structure exhibit an anomalous increase in the flow stress as a function of temperature. The theoretical models that have been proposed to explain this behavior are based upon consideration of a thermally activated cross slip of screw dislocations from {111} to {010}. These models assume that the dissociation of the a superlattice (SL) dislocation occurs by the formation of an anti-phase boundary (ABP) which is bounded by two a/2 superpartial (SP) dislocations with parallel Burgers vectors.

High-resolution electron microscopy of nanostructured materials

1995 ◽  
Vol 53 ◽  
pp. 172-173
Author(s):  
M. José-Yacamán
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Nanostructured Materials ◽  
High Resolution Electron Microscopy ◽  
Hrem Image ◽  
Small Particles ◽  
Resolution Electron ◽  
Nanophase Materials

Electron microscopy is a fundamental tool in materials characterization. In the case of nanostructured materials we are looking for features with a size in the nanometer range. Therefore often the conventional TEM techniques are not enough for characterization of nanophases. High Resolution Electron Microscopy (HREM), is a key technique in order to characterize those materials with a resolution of ~ 1.7A. High resolution studies of metallic nanostructured materials has been also reported in the literature. It is concluded that boundaries in nanophase materials are similar in structure to the regular grain boundaries. That work therefore did not confirm the early hipothesis on the field that grain boundaries in nanostructured materials have a special behavior. We will show in this paper that by a combination of HREM image processing, and image calculations, it is possible to prove that small particles and coalesced grains have a significant surface roughness, as well as large internal strain.

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 Tilt Boundaries by Ultra High Resolution Electron Microscopy

1984 ◽  
Vol 41 ◽  
Author(s):  
W. Krakow ◽  
J. T. Wetzel ◽  
D. A. Smith ◽  
G. Trafas
Keyword(s):  
High Resolution ◽  
Grain Boundary ◽  
Structural Information ◽  
Theoretical Work ◽  
High Resolution Electron Microscopy ◽  
Point Of View ◽  
Experimental Point ◽  
Structure Information ◽  
Resolution Electron ◽  
Tilt Boundaries

AbstractA high resolution electron microscope study of grain boundary structures in Au thin films has been undertaken from both a theoretical and experimental point of view. The criteria necessary to interpret images of tilt boundaries at the atomic level, which include electron optical and specimen effects, have been considered for both 200kV and the newer 400kV medium voltage microscopes. So far, the theoretical work has concentrated on two different [001] tilt bounda-ries where a resolution of 2.03Å is required to visualize bulk lattice structures on either side of the interface. Both a high angle boundary, (210) σ=5, and a low angle boundary, (910) σ=41, have been considered. Computational results using multislice dynamical diffraction and image simulations of relaxed bounda-ries viewed edge-on and with small amounts of beam and/or specimen inclina-tion have been obtained. It will be shown that some structural information concerning grain boundary dislocations can be observed at 200kV. However, many difficulties occur in the exact identification of the interface structure viewed experimentally for both [001] and [011] boundaries since the resolution required is near the performance limit of a 200kV microscope. The simulated results at 400kV indicate a considerable improvement will be realized in obtain-ing atomic structure information at the interface.

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