Single ion impacts on an In 0.22Ga 0.78As/GaAs(100) surface observed by atomic force microscopy

Very flat In _0.22Ga _0.78As layers grown by metalorganic vapour phase epitaxy (MOVPE) on GaAs(100) surfaces were bombarded with a low dose (10 ¹¹ ions cm ^-2) of arsenic and boron ions at 35 keV. Atomic force microscopy (AFM) observations show craters with average diameters of 14.6 nm and 11.4 nm for As ⁺ and B ⁺ respectively. It is found that there is a 1:1 relationship between the areal density of craters and ion dose. This implies that each crater is correlated with a single ion impact. The mechanism of the formation of the craters is discussed. We suggest that the craters arise from the combined effects of sputtering, surface mass transport around the ion track and atomic displacements in the cascade.