A METHOD TO PROFILE ION-BEAM LINE EXPOSURES IN-SITU USING STM

The profile of a line defined by focused ion beam irradiation of GaAs( 100) was characterised in situ using scanning probe microscopy. Curren t-imaging tunnelling spectroscopy was used to characterise the surface defects induced by the high energy Ga+ ions. Spatially reproducible f eatures, approximately one per ion and 2-3 nm in diameter, were observ ed in the irradiated surface. Differential conductance spectra of thes e features indicated that the image contrast was due to acceptor state s induced in the surface bandgap. The density of these defects was use d to form a profile of the ion beam in the semiconductor surface. The resulting profile was in excellent agreement with the two-Gaussian fit reported by previous work.