In a conventional scanning electron microscope, a thin, grounded conductive coating is applied to specimens that are poor electrical conductors to prevent retarding and deflection of the incident electron beam. in a variable pressure or environmental scanning electron microscope (ESEM), excess charge on the surface of uncoated poorly conducting specimens is balanced using ionized environmental gas. Ionized gas in environmental mode and grounded conductive coatings in conventional or high vacuum mode minimize charging at the specimen surface, however significant charge trapping may still occur in the implanted sub-surface regions of poorly conducting materials. A small fraction (<10-6) of the incident electrons are trapped at irradiation induced or pre-existing defects within the irradiated specimen. The trapped charge induces a highly localized electric field which can result in electro-migration and micro-segregation of charged mobile defect species within the irradiated micro-volume of specimen.
Performance of X-ray Microanalysis in the Variable Pressure or Environmental Scanning Electron Microscope
