The oxidation of metal films

Mechanistic information can be obtained by perturbing the oxidation reaction and determining the rate change. A potential gradient was applied across growing Al2O3 films. The oxidation rate was monitored by the resistance along the evaporated Al film- as oxide thickness increased and metal was consumed film resistance R increased. A section of the -1/R vs t plot for an experiment at 50 C is given. Whenever the O-Al2O3 interface was made negative to the Al reaction rate increased, an effect consistent with slow ion transport across the oxide at 200 to 400 C. Chromium, Ni, Zn show a transition in growth mechanism with increased oxidation temperature, but Al (and Cr at lower temperatures) behaves as if the slow step in the reaction mechanism were field-assisted ion transport, that is, the Mott-Cabrera mechanism. 22 ref.--EPAA/AF.