In the work carried out at LIMMS (Laboratory for Integrated Micro-Mechatronic Systems) by Dr F Rose, in collaboration with Prof H Kawakatsu and Prof H Fujita, an in situ monitoring of Ga dot and ripple formation by FIB sputtering on GaAs(001) is reported. It shows for the first time FIB movies that allow the formation and diffusion of dots and ripples in real time to be studied.

The results strongly suggest that under continuous sputtering, dots diffuse and self-assemble to form ripples. With increasing ion dose the evolution of the surface morphology of sputtered GaAs(001) can be classified in three regimes. At low dose, Ga dots (50–460 nm) are formed and diffuse on the surface under continuous FIB irradiation. At intermediate dose, Bradley-Harper type ripples appear (1150 ± 25 nm pseudo-period). At higher doses, additional sputtering flattens the ripples which are eroded into microplanes.