Electron microscopic and ellipsometric studies on oxidized aluminium layers

Abstract

Epitaxial and polycrystalline Al thin films were deposited in HV on cleaved mica and glass substrates. The Al films were oxidized by thermal and electrolytic processes. The optical constants n and k of virgin and oxidized Al films have been determined by ellipsometry in the 365–579 nm wave length range at the four intensive Hg lines. The apparent values of n and k of the Al films exhibited some correlations with their microstructure revealed by electron microscopy explaining discrepancies in contradictory literature data. Using the same optical constants for the Al substrate after oxidation, a reasonable agreement of the oxide thickness was found at the four Hg lines, with the refractive index n ox =1.77, evaluating the ellipsometric measurements. Ellipsometric studies were completed by reflectance measurements.