H. Höchst

XPS investigation of simple metals

The theory for the photoemission process is inspected taking into account many body effects. Simple equations for the analysis of experimental spectra are deduced which allow to determine the relative importance of the many body effects to the observed spectrum. The core level spectra for Be, Na, Mg and Al metal are analysed quantitatively yielding the magnitude of the intrinsic and extrinsic contribution to the plasmon creation.

I. XPS study of 3d-metal ions dissolved in aluminium

The core and valence band spectra of diluteAlMn,AlNi andAlCu alloys have been investigated by x-ray induced photoemission spectroscopy (XPS). The 2p levels of Mn and Cu inAlMn andAlCu change only slightly compared to their properties in the pure metals, whereas those of Ni inAlNi lose both their asymmetry and the two hole satellite. The 3s spectra of Mn inAlMn show a splitting of 2.9 eV, as compared to 4.3 eV in Mn metal. This indicates that inAlMn the Mn ion is magnetic, at least in the time scale of the XPS measurement. The valence band spectra of the alloys (and ofAlFe andAlCo) show virtual bound states with a width of about 1.5 eV and a distance relative to the Fermi energy which increases with increasingd-occupancy. The energy of the Al plasmons increase with increasingd-metal content.

Photoelectron-spectroscopy investigation and electronic properties of LiNbO3 crystal surfaces

The electronic properties of Ar-ion and electron bombarded single-crystal surfaces of LiNbO3 have been investigated at room temperature by ultraviolet photoelectron spectroscopy (UPS) and x-ray excited photoelectron spectroscopy (XPS). In crystals reduced in this way, the loss of oxygen is accompanied with a loss of lithium and the creation of Nb4+ and Nb3+ ions. The relative concentrations of the various defects have been determined from their corresponding XPS core line spectra. When surface defects are produced an emission in the region of the bulk band gap appears. This gap emission is identified as arising from Nb 4d electrons due to the reduction of Nb5+ ions to Nb4+ and Nb3+ ions. The different behaviour of the gap emission upon surface treatment in the UPS and the XPS spectra is discussed.

II. XPS study of 3d-metal ions dissolved in noble metals

Valence and core level spectra ofAgMn,AuFe,AuCo,AuNi,CuFe,CuCo andCuNi will be reported. Clearly defined virtual bound states (vbs) can only be detected in the spin fluctuating systemsAuNi andCuNi. An increase in the density of states near the Fermi energy, in the region of the flats-p band of the host metal is observed in the other magnetic alloys. There are indications that a large hybridization between the impurity and the host metald-electrons exist. The impurity core levels show satellites. They can originate from the emission from real isolated impurities and from many body effects.

XPS study of U, UNi5, UCu5 and UNi0.5Cu4.5

Abstract Core and valence band spectra of U metal and the intermetallic compounds UNi 5 , UCu 5 and UNi 0.5 Cu 4.5 have been measured by X-ray excited photoelectron spectroscopy (XPS). The data indicate that in UNi 5 the configuration is 5f 3 , and in UCu 5 and Uni 0.5 Cu 4.5 a mixed valence configuration with fewer 5f electrons than in UNi 5 is present.

XPS-valence bands of iron, cobalt, palladium and platinum

Abstract XPS valence band spectra of iron, cobalt, palladium and platinum are reported. They show good agreement with theoretical density of states curves that have been corrected for instrumental resolution, electron-hole interaction, matrix element modulation, lifetime of the photohole and inelastic electron electron scattering.

X-ray excited photoelectron spectra of LiNbO3: A quantitative analysis

X-ray excited photoelectron spectra (XPS) using monochromatized Al — Kα radiation (ℏω =1,486.7 eV) have been analysed quantitatively. The intensities of the various core lines (Li(1s), O(1s), O(2s), Nb(3s), Nb(3p), Nb(3d), Nb(4s), Nb(4p)) normalized to the intensity of the Nb (3d5/2)-line, show good agreement with those calculated with theoretical values for the photoabsorption cross section of the free atoms and the theoretical estimates of the dependance of the electron escape depth on the electron kinetic energy. From the energy loss spectra observed at the high binding energy side of the XPS core lines the energy loss function Im {−1/ε(ω)} is calculated and compared to published optical data. This comparison yields directly the total electron escape depth as function of the electron energy over a large energy range.

XPS valence band spectra of Nb3Sn, Nb and Sn

Abstract XPS valence band spectra of Nb 3 Sn, Nb and Sn have been obtained under high resolution. The 4 d band structure in the Nb 3 Sn spectrum is similar to that seen in Nb metal.

X-ray photoelectron emission from iron metal

XPS-spectra of iron metal with special emphasis on the valence band region are reported. The valence band spectrum is in qualitative agreement with that obtained from UPS measurements with 21 eV photons. A comparison with theoretical density of states curves shows reasonable agreement, if the matrix element modulation, lifetime broadening, the inelastic scattering of electrons, the production of electron hole pairs by the photohole, and the instrumental resolution are taken into account. The production of electron hole pairs by a photohole in the valence band seems to be smaller than by a photohole in a core level. This is not unexpected in view of the delocalized nature of these valence electrons.

The XPS valence band of nickel metal

The XPS valence band spectrum of evaporated nickel is compared with a theoretical density of states curve and with a synthetic density of states curve obtained by adding two XPS valence band spectra of copper shifted by 0.3eV with respect to each other. Both calculated curves agree with the main features of the XPS valence band spectrum.