Valence band study of Mg2Si by Auger spectroscopy

Previous XPS measurements of Mg2Si revealed three valence bands which were all assigned to the Si 3s and 3p states based on a completely ionic model of the bonding in Mg2Si that assumed no occupied Mg 3s or 3p states. Auger spectroscopy is element specific so that the local density of states of Mg and Si can be measured separately. The L1L23V and the L23VV Auger spectra of Mg in Mg2Si were measured from a single crystal of Mg2Si cleaved in UHV. The L23VV spectrum showed the involvement of the Mg 3p state in the upper two valence bands in agreement with recent calculations. More surprisingly the L1L23V spectrum gave evidence of the presence of the Mg 3s state in the lowest energy valence band that had not been predicted. The Auger results gave evidence of covalency in the bonding of Mg2Si.