Nonlinear Electronic Stopping for Slow Ion in a Narrow Band Gap Semiconductor: Formation of Chemical Bonds during Collision

TL;DR

This study uses time-dependent density-functional theory to explore how slow ions lose energy in silicon, revealing that chemical bond formation during collisions significantly affects electronic stopping power, especially at low velocities.

Contribution

It demonstrates that chemical bond formation during ion collisions contributes to energy loss, a phenomenon not previously accounted for in electronic stopping models.

Findings

Chemical bonds form during slow ion collisions in silicon.

Bond formation enhances energy loss at low velocities.

Electronic stopping behavior transitions from non-metallic to metallic with velocity.

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 0.6 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 a complete vanish of hard threshold. An analysis of the electron localization function allows us to arrive at the following conclusion: the long duration of encounter process between the host atoms and the projectiles with low velocities makes possible the formation of chemical bonds with relative high bond order. The continuous formation and breaking of chemical bonds provides an additional effective energy loss channel.