Study of the oxidation of aluminum and copper: From oxygen surface chemisorption to the growth of continuous oxide films

The understanding of the oxidation processes is key to manipulating oxidation for modifying materials with tailored properties, specially, the fundamental understanding of the nature of the interaction at the oxygen/metal and metal/oxide interface is crucial for many important technological processes. In this research work, we focus on the growth of microscopically thin oxide overlayer on bulk materials including Al(111) and Cu(110) at relatively low temperature range.;We study the effect of oxygen pressure and temperature on the self-limiting oxidation of an Al(111) surface for oxygen pressures varying from 1x10-8 - 5 Torr. Using x-ray photoelectron spectroscopy measurements, we monitor the oxidation kinetics and the oxide film thickness for different oxidation times, pressures and temperatures. The Mott potential, oxide growth rate, oxide film limiting thickness and the density of oxygen anions on the oxide surface are determined from the measured oxidation kinetics. These quantities show a Langmuir isotherm dependence on the oxygen gas pressure and temperature. Water vapor was employed as an oxidizer for comparative study of the formation of the self-limiting oxidation behavior. We find that oxidation with water vapor results in a weaker Mott potential and thus a thinner limiting thickness of the oxide film than oxidation with molecular oxygen.;A comparative study is carried out on the oxidation of Cu(110) which results in oxygen chemisorption induced surface reconstructions and subsequent formation of crystalline oxide phases. From an interplay between x-ray photoelectron spectroscopy and variable temperature scanning tunneling microscopy, the structural response of the Cu(110) surface exposed to a wide range of oxygen gas pressure and temperature is determined. The results show that the (2x1) → c(6x2) transformation is a temperature dependence process which reveals that the formation of both the (2x1) and c(6x2) phases takes place in a metastable equilibrium with the surrounding oxygen atmosphere, demonstrating the existence of kinetic limitations to the surface phase transition.