scanning+electron+microscope+(SEM)

=__**Scanning Electron Microscope (SEM)**__= Jessie Terrano The Scanning Electron Microscope (SEM) is an instrument that takes images of a sample by scanning the sample with a focused electron beam, under low or high vacuum.

Figure 1: SEM set up at SUNY Oswego

The images taken by an SEM are constructed by the electron interaction with the surface of the sample, differing by composition and topography (1). Often SEMs create secondary electron and back-scatter electron signals (1). SEMs can also create characteristic X-rays, chathodoluminescence, specimen current and transmitted electron signals. A cartoon of the inner workings of an SEM with secondary electron, backscatter and x-ray detectors is provided in Figure 2.
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Figure 2: SEM Schematic (2) The sample is placed on the stage. The camera is used to assist with aligning sample once it is in the instrument.

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Scanning Electron Microscopes can have large ranges of electron beam strength, electron beam diameter as well as magnification. The beam strength determines how deep the electron beam penetrates; this is useful for 3D samples. Many SEMs have the beam strength adjustable between as low as <1kV and as high as 40kV. Beam diameter determines how much of the sample you can see at once and can vary from 0.4nm to 5nm. It is also common for SEMs to have magnifications as low as 10x and all the way up to and beyond 500,000x. All these possible adjustments make the instrument useful for a large variety of samples.

This instrument technique is useful for getting a close, real image of a substance. Understanding the structure of a surface could provide a lot of information. Physically, an SEM image could reveal the texture of a small sample or help understand how an organism interacts with its environment. Chemically, provided a good interpretation of the image is possible, one could discern whether or not a substance is hydrophobic or hydrophyllic; or possibly find where reaction or activation sites are located on a specimen.
 * Uses of the SEM **

The first SEM image was taken in 1935 by Max Knoll, a German electrical engineer. Knoll and his co-worker Ernst Ruska invented the first electron microscope in 1931 (3). Knoll had created an image of silicon steel that showed electron channeling contrast (4). In 1937, Manfred von Ardenne improved on the scanning electron microscope design and function, had it patented, but never create a commercial version of the instrument (5). It wasn’t until 1965 when Professor Sir Charles Oatley and student Gary Stewart further improved the SEM and marketed it.
 * History **

A new advancement of a nanomanipulation system inside the scanning electron reduces the risk of contamination because opening the high-vacuum chamber is less frequent using this system (10).
In the article “Flow-Through Pore Characteristics of Monolithic Silicas and Their Impact on Column Performance in High-Performance Liquid Chromatography”, the authors used SEM imaging to determine the pore and skeleton diameters of their silica samples (6). In the article “Microstructure Characteristics and Mechanical Properties of Al 413/Mg Joint in Compound Casting Process”, the authors found that a trilayer of uniform interface was formed during their casting process (7). In the article “Vertical Arrays of SiNWs-ZnO Nanostructures as High Performance Electron Field Emitters”, the authors used SEM imaging to confirm that the proper array structures were formed when using their new synthesis technique to create them (8). The SEM has allowed researchers to observe the morphologies of the discharge product from lithium-oxygen batteries which indicates an uneven distribution of ionic and electronic conductivities (11). Nerve tissue morphology and neuroregenerative properties were able to be investigated and axonal outgrowth could be identified using the SEM (12).
 * Recent Research **

1. Goldstein, G. I.; Newbury, D. E.; Echlin, P.; Joy, D. C.; Fiori, C.; Lifshin, E. (1981). //Scanning electron microscopy and x-ray microanalysis//. New York: Plenum Press. 2. [] 3. http://www.nobelprize.org/nobel_prizes/physics/laureates/1986/ruska-autobio.html 4. Knoll, Max (1935). " Potentiel charging and secondary emission electron- irradiated body ." //Journal of Technical Physics // 5. V on Ardenne M. (1937) “Improvements in electron microscopes.” 6. Skudasa, R.; Grimesb, B.A.; Thommesc, M.; Unger, K.K.. (2009) “Flow-Through Pore Characteristics of Monolithic Silicas and Their Impact on Column Performance in High-Performance Liquid Chromatography.” //Journal of Chromatography A// 7. Hajjari, E.; Divandari, M.; Razavi, S. H.; Homma, T.; Kamado, S. (2012) “Microstructure Characteristics and Mechanical Properties of Al 413/Mg Joint in Compound Casting Process.” //Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science// 8. Devarapalli, R. R.; Shinde, D. R.; Barka-Bouaifel, F.; Yenchalwar, S. G.; Boukherroub, R.; More, M. A.; Shelke, M. V. (2012) “Vertical Arrays of SiNWs-ZnO Nanostructures as High Performance Electron Field Emitters.” //Journal of Materials Chemistry// 9.[] 10. Zhang, Y. L., Zhang, Y., Ru, C., Chen, B. K., & Sun, Y. (2013). A load-lock-compatible nanomanipulation system for scanning electron microscope. //Mechatronics, IEEE/ASME Transactions on//, //18//(1), 230-237. 11. Zheng, H., Xiao, D., Li, X., Liu, Y., Wu, Y., Wang, J., ... & Li, H. (2014). New Insight in Understanding Oxygen Reduction and Evolution in Solid-State Lithium–Oxygen Batteries Using an in Situ Environmental Scanning Electron Microscope. //Nano letters//, //14//(8), 4245-4249. 12. Szarek, D., Marycz, K., Laska, J., Bednarz, P., & Jarmundowicz, W. (2013). Assessment of In vivo behavior of polymer tube nerve grafts simultaneously with the peripheral nerve regeneration process using scanning electron microscopy technique. //Scanning//, //35//(4), 232-245. 13. Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2008). //Molecular biology of the cell// (5th ed.). New York: Garland Science.
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