A scanning electron microscope (SEM) produces images of sample with resolution better than 1 nanometer by scanning it with a focused beam of thermionically emitted electrons. When the primary electron beam interacts with the sample, the electrons lose energy by repeated random scattering and absorption within an excitation area. The beam current absorbed by the specimen can be detected and used to create images of the distribution of specimen current.
The electrons in the beam interact with electrons in the excitation area of the sample producing various signals that can be detected and that contain information about the sample’s surface topography and composition. The beam’s position is combined with the detected signal to produce a pixel. Each pixel of computer videomemory is synchronized with the position of the beam on the specimen in the microscope, and the resulting image is therefore a distribution map of the intensity of the signal being emitted from the scanned area of the specimen.
SEM combined with energy dispersive X-ray spectroscopy (EDS) can be used to measure the chemical and physical characteristics of particles as small as 300 nm. Photomicrographs of individual particles can be acquired to provide particle morphology. Statistical methods or user-defined classification rules are used with EDS to sort particles into distinct particle classes based on compositional characteristics.
SEM enables secondary electron imaging of topographic features with magnifications up to 50,000X and spatial resolution better than 5 nm. Backscatter electron imaging enables analysis of chemical phase differences, EDS allows for quantitative elemental analysis, and X-ray imaging can produce elemental line scans and maps.
If you would like to find out more about our Scanning Electron Microscope or other technologies and services provided by American Assay Labs, please contact us and we’ll be glad to assist you with your goals.