Scanning Electron. Microscopy. Laboratory session in the course âModern Imaging Methodsâ. Lab assistants: Haiping Lai, Amine Yousfi and Anna Jansson.
SEM Scanning Electron Microscopy Laboratory session in the course “Modern Imaging Methods” Lab assistants: Haiping Lai, Amine Yousfi and Anna Jansson
1 !m
“SEM-image of an etched feature made in a Dual Beam-FIB-SEM”
Introduction The scanning electron microscope (SEM) is a powerful and frequently used instrument, in both academia and industry, to study, for example, surface topography, composition, crystallography and properties on a local scale. The spatial resolution is better than that of the optical microscope although not quite as good as for the transmission electron microscope (TEM). The SEM has an extremely large depth of focus and is therefore well suited for topographic imaging. Besides surface topographic studies the SEM can also be used for determining the chemical composition of a material, its fluorescent properties, the formation of magnetic domains, and more.
Historical Background The first SEM instrument was designed by Stinzing and Knoll in Germany in the early 30’s. Zworykin and his collaborators in the US further developed the instrument but they were still not able to achieve an acceptable signal-to-noise ratio. The design of the modern SEM is based mainly on the development work by Oatley and Nixon in Cambridge and the first commercial version of a SEM was designed by Stewart and Snelling in 1965. The more recent computer development has also strongly increased the performance of SEMs as well as the possibilities of image analysis.
Principle The specimen is bombarded by a convergent electron beam, which is scanned across the surface. This electron beam generates a number of different types of signals, which are emitted from the area of the specimen where the electron beam is impinging, see Figure 1.
