Imaging and Microanalysis in Environmental Scanning Electron Microscopy

A variety of gas cascade amplification and signal detection strategies have evolved for use in low vacuum and environmental scanning electron microscopy on poorly conducting specimens. These detectors have been optimized to perform well under various limitations on the range of gas pressure and working distance which may be imposed by experimental requirements. All of the detectors must produce high gains, low backgrounds, and generate a sufficient positive ion flux to the specimen to enable charge neutralization. The underlying principles of operation of each detector type are discussed, along with the range of experimental conditions appropriate to each.