Direct Electron Detector
There are a variety of technologies available for detecting and recording the images, Electron diffraction, diffraction patterns, and Electron energy loss spectroscopy, electron energy loss spectra produced using transmission electron microscopy (TEM). Traditional detection techniques Traditionally, TEM images or diffraction patterns could be observed using a fluorescent viewing screen, consisting of powdered ZnS or ZnS/CdS, which is excited by the electron beam via cathodoluminescence. Once the microscopist could see a suitable image on their viewing screen, images could then be recorded using photographic film. For electron microscopes, film typically consisted of a gelatin and silver halide emulsion layer on a plastic support base. The silver halide would be converted to silver upon exposure to the electron beam, and the film could then be chemically developed to form an image, which could be digitized for analysis using a film scanner. In modern TEMs, film has largely been repla ...
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Electron Diffraction
Electron diffraction is a generic term for phenomena associated with changes in the direction of electron beams due to elastic interactions with atoms. It occurs due to elastic scattering, when there is no change in the energy of the electrons. The negatively charged electrons are scattered due to Coulomb forces when they interact with both the positively charged atomic core and the negatively charged electrons around the atoms. The resulting map of the directions of the electrons far from the sample is called a diffraction pattern, see for instance Figure 1. Beyond patterns showing the directions of electrons, electron diffraction also plays a major role in the contrast of images in electron microscopes. This article provides an overview of electron diffraction and electron diffraction patterns, collective referred to by the generic name electron diffraction. This includes aspects of how in a general way electrons can act as waves, and diffract and interact with matter. It a ...
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