Time-dependent characteristics of secondary electron emission

Abstract

The recent development of the time-resolving capability for scanning electron microscopy (SEM) enables it to be a real 4D space-time imaging technique, which is extremely suitable for investigating the ultrafast dynamic processes concerned with secondary electron emission (SEE). This paper attempts to investigate the dynamic SEE process with the aid of a Monte Carlo method; the understanding of the mechanism will surely benefit the construction and application of various kinds of time-resolved SEMs. Our simulation modeling is based on the use of the Mott cross section and a dielectric function approach for the respective description of the electron elastic and inelastic scattering. One secondary electron is assumed to be produced in an inelastic scattering event, and the owned kinetic energy enables it to transport and produce other secondary electrons, forming the cascade production process. From the simulation, not only the time delay of SEE from the incidence instant of primary electrons but also the time dependences of the involved physical quantities, including the energy-, depth-, direction-, emission site-, and production site-distributions can be theoretically derived. The calculations provide useful knowledge on the time dependence of SEE from the theoretical perspective for the applications to the available time-resolved SEMs.