Surface topology of GaAs(100) after focused ion beam implantation of Si++

GaAs(100) was implanted with Si++ doses ranging from 3 x 10(13) to 3 x 10(16) cm(-2) using a focused ion beam. The surface topology-and roughness of implanted lines and squares was studied by atomic force microscopy. Above a threshold dose, protrusions of the ion beam treated areas in the range of 1-15 nm in heights and an increase in surface roughness were found. The height of the protrusions and surface roughness increase with increasing implantation dose up to a saturation level. Both the onset of substrate bulging and saturation of the effect are both dependent on the linewidth of the implant. Different causes for the protrusions are discussed. From Monte Carlo simulations, it is deduced that the volume expansion is most likely due to the creation of vacancies during implantation. (C) 1997 American Institute of Physics.