In situx-ray studies of native and Mo-seeded surface nanostructuring during ion bombardment of Si(100)

Native and Mo-seeded nanostructuring of the Si(100) surface during Ar+ ion bombardment is investigated by means of real-time grazing-incidence small-angle x-ray scattering and atomic force microscopy. During off-axis bombardment at room temperature, the native early-stage growth kinetics of nanoripples on the surface is found to be in reasonable overall agreement with theoretical predictions, particularly when an ion impact induced lateral mass redistribution term is included. For normal-incidence bombardment at room temperature, a native short wavelength smoothing of the amorphized Si surface is observed, suggesting that ion impact induced lateral mass redistribution dominates the Bradley–Harper instability. During 5% Mo-seeded normal-incidence bombardment at temperatures up to 450 °C, nanodots form with heights decreasing as the substrate temperature increases. This trend is counter to that typically observed for the growth of large cone structures on metals and suggests that the primary effect of thermal energy here is in promoting surface smoothing, rather than increasing diffusion of seed atoms to form protective clusters. During seeded bombardment at 650 °C the surface remains crystalline and surface corrugations exhibit dynamic scaling characteristic of surface diffusion-driven instabilities. This is the same behavior as is found in the absence of seeding and its presence suggests that at this concentration seeding does not play a large role during normal-incidence bombardment of the Si surface at high temperatures.