Imaging and Microanalysis of Non-Conducting Materials in the Lowvoltage FE-SEM: Challenges and Strategies

Abstract

Under high-energy electron bombardment, electrical charge can rapidly build up in non-conducting materials. The electron-induced charging process is very complex and is still not well understood. Injection of energetic electrons into insulators generates electron-hole pairs which can be localized at pre-existing or newly created charge-trap centers. Charging of insulators results from a balance between the emission of secondary electrons and the diffusion and trapping of incident electrons. In the SEM, charging is usually a dynamic process: the degree of specimen charging depends on the energy and the dose of the incident electrons, the image magnification, the pixel dwell time (PDT), and the history of the electron irradiation of the specimen. Although the degree of charging can be reduced by varying the energy of the incident electrons, charging of non-conducting specimens cannot be completely eliminated due to variations in the local SE yield across the specimen surface and the presence of charge-traps inside the specimen.