X-ray-emission studies of chemical bonding in transition-metal silicides

Abstract

We present Si L2 3 emission-band spectra of a series of 3d and 4d transition-metal (TM) silicides, together wtih Si E emission-band spectra of four 3d TM disilicides. The data are compared with augmented-spherical-wave density-of-states (DOS) calculations, and good agreement is found. The trends we find are explained with a general scheme for chemical bonding in TM silicides. The differences between the experimental data and the calculated DOS curves are tentatively attributed to self-energy effects.

Electronic structure of Ni and Mo silicides investigated by x-ray emission spectroscopy and density functional theory

“…This is at odds with the long-standing interpretation of this feature as being mostly nonbonding. 11,20,29 We note that this bonding interaction encompasses a finite contribution from Si p states in the disilicide case, in accord with the stronger Si-Si bonding in these compounds. On the empty-state side, some Si s states are observed to hybridize with the metal d states as well, between 0 and 5 eV.…”

“…We discuss them starting from higher binding energies. The main contribution to the spectral intensity at the highest binding energy ͑from −14 to −7 eV͒ arises from the Si s states, which was previously reported to be a feature of the electronic structure of mono-, di-, and trisilicides, 11,18,20,22,29,44,47 and of metalrich silicides but with a strongly reduced intensity. 21 Our calculations show that the compound composition affects the shape of this Si s feature rather than its intensity, as it is found much sharper for the metal-rich silicides in comparison with the disilicides, consistent with the decrease in the number of Si-Si near neighbors in the metal-rich compounds ͑cf.…”

“…[25][26][27][28] A few studies combining calculated and XES spectra of metal silicides have been previously reported, but the XES data are limited to Si. 12,29,30 We take here a step forward and present a more complete set of XES data consisting of the metal d and the Si p and sd states, thus allowing a greater experimental insight into the bonding mechanisms.…”

Valence-Band Structure Features of Nickel Disilicide Films

“…Both calculated by us and experimental [5,6,8,9] X-ray emission spectra of different series for all atoms of the two types of films are given in Figs. 5, 6.…”

“…5. X-ray emission Si-L 2,3 spectra of NiSi 2 : (a), (b) from the interior and nearsurface atoms of the second type film; (c), (d), (e) from the interior, intermediate and surface atoms of the first type film; (f), (g) experimental results of [9], [5] for bulk and film samples, respectively this figure represent a distribution of silicon p-states in the valence band. The differences in the shapes of these spectra are mainly due to the decrease of the core 2s-level width in comparison with the width of the 1s-level [29].…”