The application of high-resolution SEM and EPMA to the study of coatings and interfaces of materials

Author(s):  
Joseph I. Goldstein

Microchemical and micro-structural analysis are often required when characterizing coatings and interfaces in materials. For coatings the interface between substrate and coating and between coating and the surface are of particular interest. The scanning electron microscope (SEM) and electron probe microanalyzer (EPMA) are often employed in characterizing interfaces in materials particularly because solid samples can be studied and sample preparation is usually restricted to developing a suitable flat polished surface for analysis. Both these instruments are essentially the same although the EPMA is equipped with wavelength dispersive detectors (WDS) and is dedicated to quantitative microchemical analysis.The spatial resolution for high resolution SEM where microstructural analysis of the surface is desired is now in many ways comparable to the transmission electron microscope (TEM). Magnifications of over 100,000 X are available in SEMs equipped with a field emission gun using the secondary electron mode. Figure 1 shows the interface region of a retained austenite region in the Tazewell iron meteorite shown in both TEM and SEM mode and Figure 2 shows the morphology of crystals, 0.3 μm wide by 1.5 μm long containing ledges 30-50 nm wide in an electrodeposited Zn coating on a steel in both TEM and SEM mode.

Author(s):  
James B. Pawley

Used in the secondary electron mode, the Scanning Electron Microscope (SEM) produces an image of the outside surface of a microscopic sample which looks very similar to what one might expect to see if the sample was a diffusely illuminated macroscopic object viewed with the unaided eye. Part of the familiarity of such an image is associated with the fact that one seems to look at the sample rather than through it, as in the case with the conventional electron microscope or the high resolution light microscope. A resulting limitation is the fact that an object of interest cannot be observed if it is below the outer surface. It has been shown (Gane and Bowden 1968) that useful surface hardness information can be obtained on a micro scale by observing the deformation produced when a small stylus, attached to a D'Arsonval meter movement, is brought to bear on the surface of a sample while it is in the SEM.


Author(s):  
A. V. Crewe

The high resolution STEM is now a fact of life. I think that we have, in the last few years, demonstrated that this instrument is capable of the same resolving power as a CEM but is sufficiently different in its imaging characteristics to offer some real advantages.It seems possible to prove in a quite general way that only a field emission source can give adequate intensity for the highest resolution^ and at the moment this means operating at ultra high vacuum levels. Our experience, however, is that neither the source nor the vacuum are difficult to manage and indeed are simpler than many other systems and substantially trouble-free.


Author(s):  
H. Tochigi ◽  
H. Uchida ◽  
S. Shirai ◽  
K. Akashi ◽  
D. J. Evins ◽  
...  

A New High Excitation Objective Lens (Second-Zone Objective Lens) was discussed at Twenty-Sixth Annual EMSA Meeting. A new commercially available Transmission Electron Microscope incorporating this new lens has been completed.Major advantages of the new instrument allow an extremely small beam to be produced on the specimen plane which minimizes specimen beam damages, reduces contamination and drift.


Author(s):  
H. Rose

The scanning transmission electron microscope offers the possibility of utilizing inelastically scattered electrons. Use of these electrons in addition to the elastically scattered electrons should reduce the scanning time (dose) Which is necessary to keep the quantum noise below a certain level. Hence it should lower the radiation damage. For high resolution, Where the collection efficiency of elastically scattered electrons is small, the use of Inelastically scattered electrons should become more and more favorable because they can all be detected by means of a spectrometer. Unfortunately, the Inelastic scattering Is a non-localized interaction due to the electron-electron correlation, occurring predominantly at the circumference of the atomic electron cloud.


Author(s):  
J. C. Russ ◽  
E. McNatt

In order to study the retention of copper in cirrhotic liver, rats were made cirrhotic by carbon tetrachloride inhalation twice weekly for three months and fed 0.2% copper acetate ad libidum in drinking water for one month. The liver tissue was fixed in osmium, sectioned approximately 2000 Å thick, and stained with lead citrate. The section was examined in a scanning electron microscope (JEOLCO JSM-2) in the transmission electron mode.Figure 1 shows a typical area that includes a red blood cell in a sinusoid, a disse, and a portion of the cytoplasm of a hepatocyte which contains several mitochondria, peribiliary dense bodies, glycogen granules, and endoplasmic reticulum.


Author(s):  
S. Wang ◽  
P. R. Buseck

Valleriite is an unusual mineral, consisting of intergrowths of sulfide layers (corresponding in structure to the mineral smythite - Fe9S11) and hydroxide layers (corresponding to brucite - Mg(OH2)). It has a composition of approximately 1.526[Mg.68Al.32(OH)2].[Fe1.07Cu.93S2] and consists of two interpenetrating lattices, each of which retains its individual structural and diffraction characteristics parallel to the layering. The valleriite structure is related to that of tochilinite, an unusual iron-rich mineral that is of considerable interest for the origin of certain carbonaceous chondrite meteorites and to those of franckeite and cylindrite, two minerals that are of interest because of their unique morphological and crystallographic properties, e.g., the distinctive curved form of cylindrite and the perfect mica-like cleavage with unusual striations and the long-period wavy structure of franckeite.Our selected-area electron diffraction (SAED) patterns and high-resolution transmission electron microscope (HRTEM) images of valleriite provide new structural data. A basic structure and a new superstructure have been observed.


Author(s):  
C. Stoeckert ◽  
B. Etherton ◽  
M. Beer ◽  
J. Gryder

The interpretation of the activity of catalysts requires information about the sizes of the metal particles, since this has implications for the number of surface atoms available for reaction. To determine the particle dimensions we used a high resolution STEM1. Such an instrument with its simple optical transfer function is far more suitable than a conventional transmission electron microscope for the establishment of particle sizes. We report here our study on the size and number distribution of Ir particles supported on Al2O3 and also examine simple geometric models for the shape of Ir particles.


Author(s):  
Edward Coyne

Abstract This paper describes the problems encountered and solutions found to the practical objective of developing an imaging technique that would produce a more detailed analysis of IC material structures then a scanning electron microscope. To find a solution to this objective the theoretical idea of converting a standard SEM to produce a STEM image was developed. This solution would enable high magnification, material contrasting, detailed cross sectional analysis of integrated circuits with an ordinary SEM. This would provide a practical and cost effective alternative to Transmission Electron Microscopy (TEM), where the higher TEM accelerating voltages would ultimately yield a more detailed cross sectional image. An additional advantage, developed subsequent to STEM imaging was the use of EDX analysis to perform high-resolution element identification of IC cross sections. High-resolution element identification when used in conjunction with high-resolution STEM images provides an analysis technique that exceeds the capabilities of conventional SEM imaging.


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