Oxidation of Aluminum Protected by Wide Band Gap MgF₂ Layers as Followed by X-ray Photoelectron Spectroscopy

Aluminum enjoys broad band reflectivity and is widely used as an astronomical reflector. However, it oxides rapidly, and this oxide absorbs very short wavelength light, which limits the performance of aluminum mirrors. Accordingly, thin transparent layers, such as films of MgF₂, are used to protect aluminum. In this study, we present an X-ray photoelectron spectroscopy (XPS) study of the chemical changes in MgF₂ - protected aluminum that take place as it oxidizes (is exposed to the air). XPS reveals the rate of Al oxidation for different MgF₂ thicknesses as determined from measurements obtained from 5 min to 8 months of air exposure. The degree of Al oxidation depends on the MgF₂ over layer thickness.

https://doi.org/10.14332/svc19.proc.0046