XPS and theoretical studies of the electronic structure of FeX and NiX (X = Al, Si, P)

Abstract

For the stoichiometric compounds FeX and NiX (X = Si, Al, P) the x-ray photoelectron spectra of valence bands are obtained and calculations of their electronic structure are carried out by the tight-binding linear muffin-tin orbital atomic sphere approximation method (TB-LMTO-ASA). A satisfactory agreement between the x-ray photoelectron spectra and the calculated density-of-states curves is obtained. It is shown that with an increase of the second-component p-electrons, hybridization of d(metal) and p(X) electrons decreases, the probability of d-p resonance increases and the contribution of p(X) states near E f increases.

Examination of the Bonding in Binary Transition-Metal Monophosphides MP (M = Cr, Mn, Fe, Co) by X-Ray Photoelectron Spectroscopy

“…The fitted valence-band spectra of the transition-metal monophosphides are shown in Figure . In general terms, the measured valence-band spectra are in excellent qualitative agreement with calculated band structures, which show a sharp Fermi edge and a narrow, metal-based, d band with a high density of states superimposed partially on a broader, largely phosphorus-based p band. − ,, They also resemble spectra previously reported for MnP, ,, FeP, , and CoSb, but the use of different excitation energies in different studies affects the photoionization cross-sections and thus modifies the peak intensities 9 Fitted valence-band spectra of sputter-cleaned samples of (a) CrP, (b) MnP, (c) FeP, and (d) CoP. …”

“…In general terms, the measured valence-band spectra are in excellent qualitative agreement with calculated band structures, which show a sharp Fermi edge and a narrow, metal-based, d band with a high density of states superimposed partially on a broader, largely phosphorus-based p band. [11][12][13]17,18 They also resemble spectra previously reported for MnP, 4,16,17 FeP, 16,18 and CoSb, 42 but the use of different excitation energies in different studies affects the photoionization cross-sections and thus modifies the peak intensities. 43 To fit the spectra presented in Figure 9 with both transition-metal and phosphorus states, they were compared to previously reported band structure calculations and XPS results.…”

“…The region 15-10 eV below E F has been attributed to P 3s states 15 whereas the broad region above it (8-3 eV) has been attributed to P 3p bonding states. 18 The transitionmetal 3d states (containing both t 2g and e g components) have been suggested to lie close to E F along with P 3p nonbonding states having a similar to slightly lower binding energy. 18 The position of the P 3p nonbonding states lying above the transition-metal 3d states has been implied previously in band structure calculations of transition-metal monophosphides, 18 as well as in the valence-band spectrum of Ni 2 P. 44 As an example, the unfitted valence-band spectrum for MnP can be compared to the P 3s, P 3p, and Mn 3d projections of the density of states, as determined from an extended Hu ¨ckel calculation (Figure 10).…”

“…18 The transitionmetal 3d states (containing both t 2g and e g components) have been suggested to lie close to E F along with P 3p nonbonding states having a similar to slightly lower binding energy. 18 The position of the P 3p nonbonding states lying above the transition-metal 3d states has been implied previously in band structure calculations of transition-metal monophosphides, 18 as well as in the valence-band spectrum of Ni 2 P. 44 As an example, the unfitted valence-band spectrum for MnP can be compared to the P 3s, P 3p, and Mn 3d projections of the density of states, as determined from an extended Hu ¨ckel calculation (Figure 10). The highest BE region can be assigned to P 3s states, the region above it to P 3p states, followed by Mn 3d states; there is also a small contribution of P 3p nonbonding states closest to the Fermi edge.…”

“…The electronic structure of some first-row transition-metal monophosphides has been previously investigated with both experimental X-ray photoelectron spectroscopy (XPS) studies [15][16][17][18] and theoretical calculations. [11][12][13]19,20 Here we describe new high-resolution XPS measurements of CrP, MnP, FeP, and CoP, with the goal of clarifying the electronic structure and bonding in these important compounds.…”