Investigating the thermal effects and oxidation of aluminum alloy 6061 using In-situ spectroscopic ellipsometry

Abstract

• In-situ spectroscopic ellipsometry on thermal effects of metal alloy • Multi-data analysis to break correlation between refractive index and oxide thickness • Discussion on Drude and interband transition • Growth of surface oxide In-situ spectroscopic ellipsometry was applied to monitor the thermally induced changes in the optical properties of aluminum alloy Al6061 and the growth of the surface oxide layer. Raw data indicate noticeable to accelerated changes at 400°C and 500°C. The simultaneous analysis of multiple data sets broke the correlation typically observed in ellipsometric analysis on metals. Dielectric functions of Al6061 at different temperatures were determined and found to have changed irreversibly after the heat treatment. Evolution of absorption features related to aluminum interband transition and the Drude absorption in the near-infrared were discussed. Morphology of the surface oxide was attributed to the lower than expected refractive index.