Results for room‐temperature oxidation of silicon using cesium ion bombardment and low oxygen exposure are presented. Bombardment with cesium ions is shown to allow oxidation at O2pressures orders of magnitude smaller than with noble gas ion bombardment. Oxide layers of up to 30 A˚ in thickness are grown with beam energies ranging from 20–2000 eV, O2pressures from 10−9to 10−6Torr, and total O2exposures of 100to 104L. Results are shown to be consistent with models indicating that initial oxidation of silicon is via dissociative chemisorption of O2, and that the low work function of the cesium‐ and oxygen‐coated silicon plays the primary role in promoting the oxidation process.