Modelling energy deposition in polymethyl methacrylate with low-energy electron irradiation

Energy deposition in dielectric materials by electron irradiation is important in evaluating irradiation effects in various applications. Herein, we developed a novel Monte Carlo model to calculate the actual distribution of energy deposition in polymethyl methacrylate (PMMA) by simulating low-energy electron transport, including secondary electron cascades. We compared the energy deposition calculated using this model with the distribution of energy loss based on the continuous slowing down approximation (CSDA). The difference in depth distribution between energy deposition and energy loss near the surface is attributed to the secondary electron emission. The characteristics of energy deposition distributions at various incident angles and primary energy were analysed. Energy depositions based on different energy loss mechanisms were classified. Approximately half of the total energy deposition was formed in paths of the secondary cascade at keV-electron irradiation. The temporal properties of energy deposition show that the fast process of energy deposition occurs first near the surface of the dielectric material, then deep inside and 1-keV electrons deposit their energy in 10^-14 s.