Abstract
Growth and dissolution of aluminum oxide layers on aluminum electrodes in 3 M H 2SO 4 was monitored using ex-situ and in-situ spectroscopic ellipsometry and ex-situ X-ray photoelectron spectroscopy (XPS). The XPS results indicate that the porous oxide as well as the barrier oxide grown in tartaric acid can be described as γ-Al 2O 3 containing no significant amounts of water. Films grown in 3 M H 2SO 4 contain about 1.5% anions. Spectroscopic ellipsometry clearly reveals the growth of a porous layer on top of a compact interphase layer. The film thickness is directly proportional to the anodization time and to the applied current density. A growth rate of 11.8 Å/s was determined for a current density of 2 mA/cm 2. The porosity of the anodic oxide layer increases with growth time. Dissolution of the anodically formed oxide layer proceeds within the pores, increasing the porosity significantly while maintaining the film thickness. Porosity during growth as well as during dissolution is a linear function of time. It is demonstrated that in-situ and ex-situ ellipsometry results for the oxide layer are in good agreement.
Published Version
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