Combining Ellipsometry and Electron Microscopy when Identifying the Initial Stages of Aluminum Oxidation. III. Laser Probe and Electron Microscopy 1

Abstract

The initial stages of vacuum oxidation of aluminum at room temperature were studied with the use of laser-ellipsometric stochastic microprobe. The optical noise of the fluctuating intensity of a laser beam focused and reflected from the surface (referred to as “noise” below) enables one to apply the stochastic model of accumulating destruction to investigating the nucleation rate, size, and typical period of accelerated growth of the new oxide phase, especially when nucleation is microscopically localized at the initial stages and nonuniformly and randomly spread over the surface. The initial stages of aluminum oxidation are discriminated. At the initial stages, the noise is related to the adsorption of oxygen atoms, which form islets of dipolar metal–oxygen domains. When a certain surface coverage with islets is reached, their lateral dipole–dipole interaction results in the quick reorientation of domains and the inclusion of oxygen in the metal with the formation of metastable nuclei of a new oxide phase. At this stage, the noise is determined by the randomness of the surface nucleation of the oxide phase. At subsequent stages, the oxide-phase nuclei gradually occupy the surface, and the noise characterizes the growth of the layer on the nonuniform original surface of the deposited aluminum layer.