Electron Beam Irradiation Effects and In-Situ Irradiation of Nanomaterials

Electron beam irradiation of specimens is often referred to as damage but is inevitable in electron microscopy as the energetic electron beam interacts with the specimen while passing through the specimen. The damage may accumulate over time and lead to visible changes in the structure or chemistry of the specimen. Therefore, electron irradiation effects should be carefully evaluated in in situ experiments in the electron microscope. Although radiation damage is normally an unwelcome artifact, under certain conditions electron irradiation can provide a tool to trigger the local structural evolution or chemical reactivity in a controllable way. The structural transformation can thus be monitored in real time with atomic resolution. Consequently, in situ irradiation experiments are beneficial to reveal the physics behind irradiation effects, explore nonequilibrium states of nanosystems and extend the technical applicability of electron irradiation. In this chapter, we summarize the physical principles of electron irradiation effects including atom displacements, surface sputtering, electrostatic charging, radiolysis, electron beam heating, and deposition. We also present some examples of electron irradiation-induced processes at the atomic scale, such as defect dynamics, phase transformations, bottom-up growth, top-down fabrication, and mechanical deformation. Particular emphasis is put on electron beam-induced processes inside the TEM where electron beam irradiation plays an important role.