The profile of an ion beam line exposure of Ga+ ions into GaAs(100) was characterized in situ using scanning probe microscopy. Current imaging tunneling spectroscopy was used to characterize the surface defects induced by the high-energy Ga+ ions. Spatially reproducible features, approximately one per ion and 2-3 nm in diameter, were observed on the irradiated surface. Differential conductance spectra of these features indicated that the image contrast was due to acceptor states induced in the surface band gap. The density of these defects was used 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 in previous work.