Non-destructive depth analysis of the surface oxide layer on Mg2Si with XPS and XAS

Depth analysis of the surface oxide layer on a Mg2Si crystal was performed with X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). In XPS, X-rays from synchrotron radiation with the energies between 2100 and 3300eV were used as the excitation sources for depth analysis. The Si 1s and Mg 1s XPS spectra show the formation of a thinner SiO2-X layer at outermost surface and a thicker MgO layer at lower surface on the Mg2Si. In XAS, total electron yield and partial electron yield (PEY) acquisition modes were used for the measurement of Si K-edge. The PEY spectrum was obtained by detecting electrons with a fixed kinetic energy of 5, 10, 20, 30, 40, or 50eV. Although the PEY spectrum with electrons of 5eV shows similar features with the total electron yield spectrum, detection of electrons with 50eV gives an increase in the ratio of a peak at 1843.7eV to the peak assigned to Mg2Si. The peak at 1843.7eV can be assigned to the formation of SiO2-X on the Mg2Si. From XPS and XAS results, it is indicated that a thinner SiO2-X layer at outermost surface and a thicker MgO layer at lower surface are formed at initial oxidation of the Mg2Si. Copyright (c) 2016 John Wiley & Sons, Ltd.