Dynamic characteristics of charging effects on the dielectric constant due to E-beam irradiation: a numerical simulation

A series of synthetic variations of material intrinsic properties always come with charging phenomena due to electron beam irradiation. The effects of charging on the dielectric constant will influence the charging dynamic in return. In this paper, we propose a numerical simulation for investigating the dynamic characteristics of charging effects on the dielectric constant due to electron beam irradiation. The scattering process between electrons and atoms is calculated considering elastic and inelastic collisions via the Rutherford model and the fast secondary electron model, respectively. Internal charge drift due to E-field, density gradient caused diffusion, charges trap by material defect, free electron and hole neutralization, and variation in the internal dielectric constant are considered when simulating the transport process. The dynamics of electron and hole distributions and charging states are demonstrated during E-beam irradiation. As a function of material nonlinear susceptibility and primary energy, the dynamics of charging states and dielectric constants are then presented in the charging process. It is found that the variation in the internal dielectric constant is more with respect to the depth and irradiation time. Material with a larger nonlinear susceptibility corresponds a faster charging enhancement. In addition, the effective dielectric constant and the surface potential have a linear relationship in the charging balance. Nevertheless, with shrinking charging affect range, the situation with a higher energy primary electron comes with less dielectric constant variation. The proposed numerical simulation mode of the charging process and the results presented in this study offer a comprehensive insight into the complicated charging phenomena in electron irradiation related fields.