P T Andrews

The M4,5N4,5N4,5 Auger spectra of Ag, Cd, In and Sn

High-resolution M4,5N4,5N4,5 Auger and M5 and valence-band photoelectron spectra of Ag, Cd, In and Sn, measured using X-ray excitation, are combined to yield the magnitude of Ueff, the Coulomb repulsion between two holes on the same atomic site. The extra-atomic relaxation contributions to Auger and photoelectron processes in these elements are determined by comparing the experimental results with atomic structure calculations. The relationship Ueff>>2W, where W is the width of the 4d band, holds for Cd, In and Sn and the M4,5N4,5N4,5 Auger spectra of these elements are in good agreement with multiplet structure calculations. Discrepancies between the observed and the calculated M4,5N4,5N4,5 spectra of Ag are interpreted in terms of its failure to satisfy the Ueff>>2W condition and the variation of Ueff with the final-state component of the Auger spectrum. It is suggested that the 3F4 component is able to decay into the Ag 4d band and is thus substantially broader than the other components of the Auger spectrum.

The Pd Auger spectra of Mg75Pd25, Al80Pd20 and Pd and their dependence on band structure

The M4,5N4,5N4,5 Auger transitions of Pd in Mg75Pd25 are shown to have the narrow spectral features and overall profile characteristic of the M4,5N4,5N4,5 spectra of pure Ag. The Auger spectra of Al80Pd20 and pure Pd are broader, and the extent of the broadening correlates with an increase in the Pd (4d) bandwidth and with the density of states at the Fermi energy. It is suggested that the differences in the Auger profile in Mg75Pd25, Al80Pd20 and Pd are due to the influence of the (4d) band on the (4d2) two-hole final states.

The localisation of 3d hole states in Fe and FeAl studied by Auger vacancy satellite spectroscopy

Abstract For Ni, Cu and Zn the occurrence of the L2L3M4,5 Coster-Kronig transitions give rise to L3M4,5-M4,5M4,5 Auger vacancy satellite transitions to low kinetic energy of the main L3M4,5M4,5 transitions. In pure Fe the intensity of the Auger vacancy satellites are negligibly small even though L2L3M4,5 Coster-Kronig occur, a fact which has been attributed to the delocalisation of the M4,5 (3d) hole state within the lifetime of the L3 hole. In this work we present Auger spectra for Fe and FeAl excited using radiation obtained on station 5U.1 of the Daresbury synchrotron. Our spectra support earlier work regarding the relative lifetime of the L3 and M4,5 hole state in Fe though our spectra are different in detail. We also show that the Fe 3d hole is significantly more localised in FeAl than in Fe.

The influence of the 4d bandwidth on the M4,5N4,5N4,5 Auger spectra of Ag in MgAg and AlAg alloys

The extent of the deviation of the Ag M4,5N4,5N4,5 Auger spectra from an atomic profile in pure Ag and its alloys with Mg and Al is shown to depend on the (4d) bandwidth. M. Cinis expression (1977) for the Auger electron spectrum, D( omega ), is used to relate the (4d) bands of these materials, determined from high-resolution photoelectron spectra, to the observed Auger spectra. An evaluation of D( omega ) for each component of the multiplet structure shows that the deviations of the M4,5N4,5N4,5 spectra from an atomic profile are due to reductions in the separation of the quasi-atomic parts of D( omega ) from atomic separations and a simultaneous transfer of intensity from the quasi-atomic to the broad parts of D( omega ). The theory predicts an absolute shift to lower kinetic energy of the Ag Auger spectra caused by the (4d) band. For the 1G4 component of the Ag Auger spectrum this shift lies between 0.2 and 0.5 eV.

Relative intensities of L2,3M4,5M4,5 principal and satellite Auger spectra of Cu

The L2,3M4,5M4,5 and L2,3M-MM4,5M4,5 Auger spectra of Cu have been measured using CuL, MgK, and AlK X-ray exciting radiation. L2M4,5M4,5 and L2,3M-MM4,5M4,5 transitions are of lower intensity relative to L3M4,5M4,5 transitions when the spectra are excited by CuL X-rays. The relative intensities of these transitions in the spectra excited by CuL and MgK X-rays are compared with calculated transition rates and assumed distributions of the initial L-shell hole population. A component of the spectrum excited by MgK X-rays agrees in intensity and position with theoretical predictions that a band-like feature should occur to high energy of the quasi-atomic L3M4,5M4,5 group.

An ultraviolet photoelectron spectroscopy study of some solid solutions of 3 d transition metals in gold and silver

The photoelectron spectra of V, Cr, Mn, Fe, Co and Ni dissolved in Au and of Mn dissolved in Ag have been measured using photon energies of 21.22 eV and 40.81 eV. The results appear to be consistent with the Friedel-Anderson virtual bound state model for noble metal-transition metal alloys, with clear evidence for the existence of localised states being seen in the spectra of AgMn, AuFe, AuNi and particularly AuCr. In AuCr the filled part of the spin-split Cr 3 d virtual bound state is found to be centred around 0.91+or-0.05 eV below the Fermi level with a full width at half maximum of about 0.70+or-0.10 eV. The localised states observed in AgMn and AuNi spectra lie approximately 2.84+or-0.05 eV and 0.40+or-0.05 eV below the Fermi level and have approximate widths of 0.78+or-0.10 and 0.59+or-0.10 eV, respectively.

X-ray photoelectron spectroscopy of Ni in Ni–Zn and Ni–Al alloys

Abstract X-ray photoelectron spectroscopy measurements on Ni in the alloys Ni, Ni 50 Zn 50 , Ni 20 Zn 80 and Ni 50 Al 50 have been made and confirm previous measurements of the band structure. The satellite lines on the Ni 2p and 3s lines are found to be present in the spectra even when the density of 3d states at the Fermi energy is low.

X-ray photoelectron spectroscopy of some Cu-Zn alloys

The X-ray photoelectron spectra of Cu0.9Zn0.1, Cu0.5Zn0.5 and Cu0.2Zn0.8 have been observed using Mg K alpha X-rays. The valence band spectra show that the Cu 3d band narrows and shifts to increasing binding energy relative to the Fermi energy as the Cu is diluted by Zn. The Zn 3d state width is also reduced as the Zn becomes more dilute. These results are suggested to be due to reduction of nearest neighbour 3d overlap.

IMPURITY AUGER-SPECTRA - A PROBE OF THE LOCAL IMPURITY DENSITY OF STATE AND THE IMPURITY ELECTRON ELECTRON INTERACTIONS

We show that the local impurity density of states and the impurity electron—electron interactions can be obtained from impurity Auger spectra. For a Ag0.95Pd0.05 alloy we find 11% Pd(d) character in the Ag d band and Pd(4d-4d) Coulomb interactions which are much larger than the virtual bound state widths.

Band-structure effects on the PdM4,5N4,5N4,5 Auger spectra of CucPd1-c and AgcPd1-c alloys

The results of SCF-KKR-CPA band-structure calculations show a split d band behaviour for AgPd alloys and a mixed band behaviour for CuPd alloys. The calculated results for AgPd alloys agree with XPS measurements. The Auger profiles of PdM4,5N4,5N4,5 transitions are very different in CuPd and AgPd alloys and the differences can be understood in terms of the Cini-Sawatzky theory of Auger lineshapes and the calculated band structures.