The interaction of oxygen with aluminium: Mainly ellipsometric aspects

Ellipsometry has been used to study oxygen chemisorption and corrosive oxidation of aluminium single crystals in the pressure and temperature ranges 10 −9−10 −2 Torr and 295–800 K respectively. Two oxidation stages have been identified. A fast initial stage was found to correspond to initial chemisorption and incorporation of oxygen and ends with the formation of a thin oxide layer via nucleation. An anomalous decrease in the ellipsometric parameter Ψ occurs during this stage. The second, slow stage corresponds to the growth of a parallel-sided oxide film; changes in both Δ and Ψ can be described classically using the Drude equations. In this region both logarithmic (500–600 K) and parabolic (650–800 K) oxidation kinetics were observed on the (111) surface. Logarithmic kinetics were accompanied by a pressure dependence of p 0.5 with oxide growth in the thickness range 5–20 Å. Parabolic growth exhibited an activation energy of 113 ± 5 kJ mol −1 with film growth in the range 15–45 Å.