Role of mass redistribution on nanoripple formation and propagation: A molecular dynamics simulation study

Abstract

Molecular dynamics (MD) is a tool suitable for investigating the formation of nanoscale patterns under low-energy ion beam irradiation. To focus on the role of impact-induced mass redistribution in ripple formation and propagation, an MD method was used in this paper to study the morphological change of a silicon surface under continuous bombardment with 30-eV argon. The atomic-scale dynamics processes of ripple formation and propagation are discussed in detail. The migration rate of surface atoms obtained as a function of an ion incidence angle by analyzing the migration of surface atoms can provide a reasonable explanation for the smooth-to-unstable mode transition of the silicon surface. The propagation of low-energy ion-induced ripples is investigated for the first time, and the ripple propagation velocities associated with four different incidence angles (40°, 50°, 60°, and 70°) are presented. The propagation velocity increases with the incidence angle, and the propagation direction is always in accordance with the incidence direction. This study can help further understand the formation and propagation mechanisms of nanoscale ripples in the experiments and provide a guide for the development and optimization of the theoretical model.