OXIDATION OF METAL-SURFACES AT 15 K - THE QUANTUM NATURE OF OXIDATION

Studies of Ta oxidation at 15 K clearly show the formation of distinct oxide species with increasing O-2 exposure, beginning with the most m etal-rich species and concluding with the formation of the bulk oxide and the buildup of a potential across the oxide layer. The formation o f this sequence in a diffusionless regime is consistent with electron tunneling leading to local potentials that allow atomic motion at low temperatures. This potential finally develops into the collective Mott potential across the layer.