The study "Scanning Electron Microscopy" presents the selection and comparison of a SE and BSE image taken from the same region of a sample. The researcher of this study aims to analyze the relative merits of the BSE image, x-ray maps and spot mode spectra…
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Secondary Electron images (SE) Vs. Backscattered Electron images (BSE)Secondary electron images are formed from the low energy electrons that are formed near the surface of the sample (Johnson). The brightness is affected by the surface topology of the specimen. For backscattered electron images, higher energy electrons formed deeper in the material are used to form the image. The result of these images is less contrast due to surface topology and more contrast due to different chemical composition (Johnson). This explains the 3D nature of the SE image in comparison to the flat BSE image, and the higher contrast of the BSE image in comparison to the SE image.Secondary electrons have lower energy compared to backscattered electrons, and so, they interact with the outer regions of the specimen by inelastic collisions. Therefore, only the surface topology of the specimen is clearly defined. This is the reason why the fibers in the SE looked clumped.The contrast in the BSE image is because of the production of backscatter electrons produced due to collisions of high energy electrons of the specimen. Parts of the specimen with higher atomic number cause higher backscatter than the lighter atomic number elements, resulting in a greater contrast, enabling a better study of the chemical composition of the specimen.The greater edge highlight in the SE image is because raised surfaces yield more secondary electrons....
The greater edge highlight in the SE image is because raised surfaces yield more secondary electrons. Images of a tilted TEM grid are provided showing a large difference in depth of field (file names DOF 1, 2, 3). 3 Calculate the depth of field from the images provided. Explain how you arrived at your answer. Compare SEM figures with the depth of field that would be available from an optical microscope for the same magnification. Large depth of field is one of the most important characteristics of SEM. The sharpness of the images recorded at low magnifications depends more on depth of field available than on small beam size (Lyman 1990). We know that depth of field, Where, d = minimum resolution of SEM W = Working distance D = aperture size Accordingly, the depth of field from the given images is computed as follows: Taking the following assumptions, d = minimum resolution of SEM= 3.5 nm = 3.5 ?10-9 m W = Working distance = as given in image in mm ?10-3 m D = aperture size= 200?m = 200?10-6 m Depth of field for first image with WD=13.0 mm= 13.0?10-3 m = 0.455?10-6 m = 4.55?10-7 m Depth of field for second image with WD=14.3 mm= 14.3?10-3 m =0.5005?10-6 m = 5?10-7 m Depth of field for second image with WD=44.3 mm= 44.3?10-3 m =1.55?10-6 m Comparison of SEM figures with the depth of field that would be available from an optical microscope for the same magnification The depth of field of SEM can be as great as 300 times that of the optical microscope. At low magnifications, below 300 to 400X, the image formed by the SEM is inferior to that of the optical microscope (Abbaschian et al 2008). At the same magnification, the depth of field that would be
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Images in TEM are obtained by focusing an electron beam on the specimen. The electrons are absorbed, transmitted, scattered or backscattered. Depending on the kind of image required by the operator, either the transmitted electrons (called direct beam) or the scattered electrons (called diffracted beam) is selected.
From this paper, it is clear that TEM has a large number of applications in innumerable fields ranging from life sciences to material science. TEM has proved to be a priceless tool for studying the ultrastructure of metals (Egerton 2005, 14). In life sciences, it is used for studying bacteria, viruses, and tissues of plants and animals.
SEM images were used to carry out size distribution analysis of the powder particles using a software package CARNOY. BSE image of the powder particles was taken and EDS was performed to get chemical information about bright particles in the powder sample.
This essay analyzes that spherical aberration also occurs in the Electron Microscopes when electrons passing through the side of the lens are refracted greater than those passing along the axis.2 (Lam, 2009); while Diffractive aberrations are brought about by the deviations from geometrical optics caused by the wave nature of light.
The author states that low-voltage electron microscopes (LVEM) have proven to be effective in comparison to High-voltage electron microscopes (HVEM). Both types of microscopes work on the same principles, but the significant different between them results from the effect of electron acceleration voltage variation.
Scanning electron microscopy (SEM), as well as other techniques such as energy dispersive spectroscopy (EDS) is an effective tool used for the identification and characterization of particulate contamination and foreign body contamination of food.
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QUESTION ONE Photoelectric effect Photoelectric effect is the process by which electrons are emitted from the surface of a photosensitive material when hit by light incidents. The intensity of the light energy determines the kinetic energy of the produced photoelectrons.
Besides, attenuation of the primary electron beam will also be lesser. This will lead to better image quality and better microanalytical capability of a TEM. Besides, minimizing molecule – electron beam interaction, better vacuum level
In the process, it gives off energy in form of X-rays. In the figure below, x-rays penetrates an atom and collides with an electron in the K-shell, strongly bound electrons, phenomena known as photon emission1. The energy of the incoming rays must be
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