Surface segregation of Sr in doped MgO: Comparison between x-ray photoelectron spectroscopy and atomistic ionic model simulations

Abstract

The surface coverage of Sr on doped MgO ceramics has been measured by angle-resolved X-ray photoelectron spectroscopy (XPS) for bulk doping levels in the range 3-1000 ppm. The experimental data are compared with results derived from atomistic simulations of the doped surface. At low doping levels Sr segregates by substitutional replacement of Mg in the top-most ionic layer of the ceramic and good agreement is found between the experimental Sr 3d:Mg 2s intensity ratio and values derived from atomistic simulation. However, at higher Sr doping levels there is evidence for build-up of Sr multilayers and formation of SrO as a discrete surface phase.