Chemical effect on the energy lose for slow ion channeling a narrow band gap semiconductor

Abstract

Using time-dependent density-functional theory, we investigate the electronic stopping power of self-irradiated silicon through non-adiabatic dynamics simulations. For specific velocities above 0.5 atom units, electronic stopping shows a generally assumed metallic behavior that is velocity-scaling. While in the lower velocity regime, the slope of electronic stopping power versus velocity changes and the overall magnitude are significantly greater than expectations, leading to the complete vanishing of hard threshold. An analysis of the electron localization function allows us to arrive at the following conclusion: the relative long duration of encounter process between the host atoms and the projectiles with low velocities makes possible the formation of chemical bonds. The continuous formation and breaking of chemical bonds provides an additional effective energy loss channel.