Temporal evolution of ripple pattern on silicon surface: An ion induced solid flow approach

In this paper, we study temporal evolution of low energy ion-beam induced parallel-mode ripple patterns and explore the possibility of applying ion induced solid flow model on our experimental data. Experiments were performed by using 500 eV argon ions at a fixed ion flux over an angular window of 51° to 72.5°-where parallel-mode ripple patterns evolve. It is observed that evolution of ripples at all angles remains in the linear regime (where the ripple wavelength remains constant and the roughness evolution follows an exponential growth) up to a certain crossover time beyond which the non-linear effects get into the act (in the form of ripple coarsening at lower incidence angles and faceting at higher ones). The intrinsic timescale, beyond which transition from the linear to the non-linear regime takes place at all angles, matches quite well with those predicted by the solid flow model. It is also observed that the non-linear regime sets in quickly at higher incidence angles.