Severe oxidation inhibited epitaxy when buried Sb profiles in single crystal silicon were formed from evaporated layers irradiated in atmosphere with a pulsed Q-switched ruby laser. Oxygen concentrations as high as 5×1017atoms/cm2 (equivalent to 105nm SiO2) were measured. However, structures prepared without the Sb layer and irradiated under identical conditions, showed no oxidation. Oxidation of Sb as a source of the measured oxygen was ruled out, while the total heating time during laser irradiation is so short (nano- to milliseconds) that normal oxidation kinetics cannot account for the amount of SiO2 measured. Irradiations in vacuum and in a helium ambient showed that the oxygen responsible for these effects is supplied from the ambient in which irradiations are carried out. Also no oxidation was observed when structures, prepared on a substrate heated to 350°C, were irradiated in atmosphere. A model to account for these oxidation effects is proposed.