The role of the Si 3s3d states in the bonding of iridium silicides (IrSi, Ir₃Si₅and IrSi₃)

Abstract

Si L 2,3 soft-x-ray emission spectra of IrSi, Ir 3 Si 5 and IrSi 3 compounds have been taken and the valence band densities of states associated with them have been analysed as functions of the concentration of Si atoms, the coordination number of Si-Ir in the iridium silicide compounds and the average distances of the Si-Si bonds in those compounds. The role of silicon 3s3d states in the bonding of the different iridium silicides is discussed. All the spectra show two regions, one associated with the low-energy Si 3s states and another one associated with high-energy Si 3s3d states. The effects of the interaction between the Si and Ir atoms in the silicides are: (a) the distribution of silicon states, even those associated with the least energetic s electrons, are modified, suggesting that the s electrons play a role in the formation of the iridium silicides; (b) the energy bandwidth corresponding to the Si 3s3d states increases up to 2.5 eV as the number of Si atoms that interact with the Ir atoms increases; and (c) there is a significant contribution from the d electrons, the fraction of the states associated with them being at least 20% of the total of states associated with the 3s3d states.

Iridium-modified Si(111) surface

“…This leads to the observation of a solid state amorphization process [5]. There are previous studies on bulk properties of iridium-silicides epitaxially grown on Si(100) and/or Si(111) [6,7]. From these studies, Ir-silicides have three known crystal phases, which can be grown selectively in the sense that each silicide phase grows in a specific temperature range and only one silicide phase grows at a given temperature.…”

Iridium silicide nanowires on Si(001) surfaces

“…There are previous studies on bulk properties of iridium silicides epitaxially grown on Si(100) and/or Si(111) [21][22][23][24]. It is known that mixing between Ir and Si has a negative enthalpy [25,26].…”