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SCANNING ELECTRON MICROSCOPY
Pages 10 (2510 words)
| Type your name here Select and compare a SE and BSE image taken from the same region of a sample. 1a. Highlight differences between the two images, referring to specific features in the images. The above micrographs represent a Secondary electron image (SE) and a Backscatter electron image (BSE) of the same region of an asbestos sample.
There is a greater contrast in the BSE image than the SE one. The fibers in the BSE image are clearer, but those in the SE image look clumped. The SE image provides a better view of the finer details of the specimen, unlike the BSE image. There is a greater edge highlight in the SE image. 2b. Using the properties or characteristics of the SE and BSE, explain the observed differences. Clearly state the contrast mechanisms in each image. 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. ...
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