Semiconductor surface diffusion: Effects of low-energy ion bombardment

We offer a revised mechanism to describe our previous measurements of surface diffusion under low-energy ion bombardment in the Ge/Si(111) system. We show that direct ion-induced motion of diffusing atoms (the effect commonly cited as important in ion beam assisted deposition) cannot account for these observations. Instead, we rationalize the results through processes in which ions create long-lived surface vacancies or spatially extended defects that heal continuously during bombardment. These ideas rationalize several important aspects of the experimental data that were previously unexplained, including the appearance of ion effects at very low ion fluxes, the simple Arrhenius behavior of the diffusivity, the rough magnitudes of the observed energy thresholds, and the ion-induced inhibition of diffusion at high temperatures.