Modification Of Optical Properties Of Magnesium Oxide (Mgo) Thin Film Under The Influence Of Ambience

MgO is used as an optical element in multilayer mirror for synchrotron beamlines applications. However, it is highly hygroscopic in nature leading to deterioration of its optical properties. In this study we have shown how the optical properties of MgO thin film modifies on its exposure to ambient condition in the energy range of 45-70 eV covering the Mg L-edge region. We have carried out energy dependent soft X-ray reflectivity measurements on freshly prepared and aged MgO thin film for determination of optical constants. It is observed that the optical constants values of the aged sample deviate from the freshly prepared sample owing to water adsorption and increasing surface roughness as confirmed from atomic force microscopy (AFM) images.