How do nanoislands induced by ion suputtering evolve during the early stage of growth?

The early evolution of GaSb nanoislands induced by ion sputtering was investigated by high-resolution atomic force microscopy. The growth of maximal nanoisland height varies logarithmically with the root-mean-square (rms) roughness in the short-time regime, beyond which it scales as the roughness, as expected from recent theoretical calculation. This is attributed to the gradual evolution of the nanoislands prior to their full formation. Furthermore, it was found that the rms roughness goes through a maximum of ∼8.6 nm before decreasing slightly with further sputtering to reach a constant value of 5–6 nm. The evolution of the island ordering is slower than the full formation of the nanoislands. These findings cannot be explained by the present Kuramoto-Sivashinsky (KS) equation and/or corresponding numerical simulation. We suggest that the more complicated KS equation, i.e., including the variation of the erosion term and its effect on the nonlinear behavior, should be considered to describe the evolution of the nanoislands induced by ion sputtering. [ABSTRACT FROM AUTHOR]