ROOM-TEMPERATURE OXIDATION OF CU(111) - PRESSURE EFFECTS

Ellipsometry has been used to follow the oxidation of the (111) face of a copper single crystal at 21 °C for oxygen pressures from 0.03-760 Torr. The pressure dependence is complex, with the short term oxide film thickness increasing to a limiting value as pressure increases, whereas the long term thickness goes through a maximum as pressure increases. The low pressure growth kinetics, as well as previously published contact potential measurements, can be described using the Cabrera-Mott theory for the formation of very thin oxide films modified to include the effects of space charge in the oxide. The rate determining step is taken to be the formation of cation vacancies at the gas-oxide interface. It is suggested that a monolayer of CuO forms on top of the Cu2O film at high oxygen pressures with a concomitant chance in mechanism. © 1979 American Institute of Physics.