Analysis of the x-ray photoelectron energy-loss background in silicides

Intermetallic compounds provide a means to investigate the mutual influence of two elements on the photoelectron fine structure and background that have developed as a result of bond formation. In the case of the aluminides we have shown that aluminium acquires a background structure that is typical of elements having a 3d valence band and concluded that there is a strong 'd' component in the bonding structure arising from pd hybridization. In this paper we report a similar analysis of the background structure in two silicides, MoSi2 and FeSi2. Both silicon and molybdenum in MoSi2 are very similar in background structure to that in their respective pure elemental states. Moreover, the plasmon structure that appears is similar to that of silicon itself. Thus we conclude that in this material 'p' character is an important feature of the bond. In the case of FeSi2 the situation is different. Here, silicon gains a pronounced background step, similar to that of iron, and the plasmon structure becomes weaker. This behaviour is analogous to that of FeAl and we conclude that this is evidence of the participation of the 'd' states of iron in bond formation. Copyright (C) 2001 John Wiley & Sons, Ltd.