Gaseous Scanning Electron Microscope (GSEM): Applications and Improvement

The imaging and the microanalysis of hydrated and insulating materials using electron beam probe methods (Conventional SEM, Auger Electron Microscopy,...) are very limited by the necessity to keep the sample under high vacuum and the presence of the charge effect. In this case the sample must be coated except when the experiment is performed at very low energy in order to avoid the charge phenomenon. Studies of vegetable and biological samples are almost impossible without degradation. In Conventional SEM (Pressure = 10-5 mbar in the specimen chamber) image quality and microanalysis results are strongly related to the size of the electron beam, the accelerating voltage and the nature of the sample. A large description of different aspects on SEM/EDS exists in the literature (Newbury et al, 1986; Goldstein et al, 1992).