The role of the Si 3s3d states in the bonding of iridium silicides (IrSi, Ir3Si5 and IrSi3)

Abstract

Si L2,3 soft-x-ray emission spectra of IrSi,Ir3Si5 and IrSi3 compounds have been takenand the valence band densities of states associated with themhave been analysed as functions of the concentration of Siatoms, the coordination number of Si-Ir in the iridiumsilicide compounds and the average distances of the Si-Si bondsin those compounds. The role of silicon 3s3d states in thebonding of the different iridium silicides is discussed. Allthe spectra show two regions, one associated with thelow-energy Si 3s states and another one associated withhigh-energy Si 3s3d states. The effects of the interaction between the Si and Ir atoms in the silicides are: (a) thedistribution of silicon states, even those associated with theleast energetic s electrons, are modified, suggesting that thes electrons play a role in the formation of the iridiumsilicides; (b) the energy bandwidth corresponding to the Si 3s3dstates increases up to 2.5 eV as the number of Si atoms thatinteract with the Ir atoms increases; and (c) there is asignificant contribution from the d electrons, the fraction ofthe states associated with them being at least 20% of thetotal of states associated with the 3s3d states.