A systematic study to determine the effect of dose and dose rate on implanting oxygen at 80 and 160 keV is reported. Samples were produced by implanting oxygen into p-type Si(100) wafers at dose rates of 5-60 μA/cm2 and doses from 3 × 1017 to 1.6 × 1018 O+/cm2 using an Eaton NV10-160 implanter. Samples were studied using cross-sectional transmission electron microscopy, scanning electron microscopy, and Rutherford backscattering spectroscopy. The results obtained suggest that dose, dose rate, and energy thresholds for pit formation in the Si top layer of SIMOX (separation by implanted oxygen) samples exist. For example, for doses of both 3 × 1017 and 4 × 1017 O+/cm2 the dose rate threshold is between 50 and 60 μA/cm2. It is also shown that the threshold for pit formation can be increased by implanting through an oxide capping layer.