Hot-electron mediated ion diffusion in semiconductors for ion-beam nanostructuring

Ion-beam-based techniques are widely utilized to synthesize, modify, and characterize semiconductors at the nanoscale. Interactions of the beam with the target are fundamentally interesting, as they trigger multi-length- and time-scale processes that need to be quantitatively understood to achieve nanoscale precision. Here we demonstrate for magnesium oxide¹ that, in a beam energy regime in which electronic effects are usually neglected, a proton beam efficiently excites oxygen-vacancy-related electrons and changes the charge state of the F-center. We quantify the beam-energy-dependent electronic excitation and the emerging ion dynamics using first-principles techniques. We further bridge time scales from ultrafast electron dynamics directly after impact to ion diffusion over migration barriers in semiconductors and discover a diffusion mechanism that is mediated by hot electrons. Our quantitative simulations predict that this mechanism strongly depends on the projectile-ion velocity, suggesting the possibility of using it for precise sample manipulation via nanoscale diffusion enhancement in semiconductors with a deep, neutral, intrinsic defect.

1. C-W. Lee and A. Schleife Nano Lett. 2019, 19, 6, 3939-3947