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Fundamentals and Applications of Scanning and Transmission Electron Microscopes

Hugo Zea

Electron microscopes are equipment that use an accelerated electron beams as probes to generated images with magnifications and resolution not possible to obtain with optical microscopes (due to fact that electron wavelength can be 100,000 times shorter than visible light photons). Electron microscopes operating in the conventional high vacuum mode require conductive imaging specimens; therefore, non-conductive materials need the deposition of a conductive layer (Au-Pd alloys, carbon and osmium, among others). Low voltage mode of modern microscopes makes possible to observe non-conductive uncoated specimens. Transmission electron microscopes require thin samples (below 100 nm), placed onto appropriate sample holders. Electron microscopes are state of the art equipment that requires high operation and maintenance standards, therefore having a clear understanding of the operation fundamentals, equipment capabilities, suitable sample preparations and appropriate results interpretation is of critical importance to use the technique in the most suitable fashion.