Ralf Nyholm

Electron escape depth in silicon

Abstract The ESCA electron escape depth in silicon is determined from the peak areas in the electron spectra from evaporated thin films. For electron energies in the region 320 eV to 3.6 keV values from 13 to 83 A are obtained. The escape depth in silicon dioxide is determined for the energies 1.6 and 3.6 keV. Binding energies and Auger energies are determined in silicon and silicon oxides.

A soft X-ray monochromator for the MAX synchrotron radiation facility☆

A high resolution soft X-ray monochromator for the 550 MeV MAX storage ring is described. The instrument combines a plane elliptical premirror collecting a large (10 mrad) horizontal angle of radiation and a modified version of the well-known SX-700 plane grating monochromator (PGM). The modification consists of changing the original ellipsoidal focussing mirror to a plane elliptical mirror. Thereby the horizontal and vertical focussing are decoupled and good imaging properties are obtained irrespective of the large horizontal acceptance angle. The MAX-PGM will be part of an experimental station for photoelectron, photoabsorption and photon stimulated ion desorption spectroscopy.

Experimental L and M Core Level Binding Energies for the Metals 22Ti to 30Zn

Accurate core level binding energies for the L and M shells in the metals 22Ti to 30Zn have been measured by means of ESCA. Comparisons with previously reported data in many cases show discrepancies of several eV. The spin-orbit splittings of the 2p subshells have been measured with high accuracy and are compared with theoretical values.

Auger and Coster-Kronig broadening effects in the 2p and 3p photoelectron spectra from the metals 22Ti-30Zn

The 2p and 3p core level widths for the metals 22Ti-30Zn have been studied by photoelectron spectroscopy. The L2L3M45 Coster-Kronig rate is found to have a maximum for Co and Ni. The Coster-Kronig broadening seems to be a simple function of the kinetic energy of the emitted electron. Absolute 2p level widths have been determined which in general show much higher accuracy than previously reported values. The presently determined widths are found to agree well with theoretical predictions. The M2M3M45 super Coster-Kronig decay channel is open in Co but not in Ni.

Design of a portable large spectral range grazing incidence instrument

A design of a small size grazing incidence instrument is presented, which offers large spectral range and high resolution without sacrificing luminosity. The instrument is particularly suited for use at synchrotron radiation sources since it can be conveniently attached to existing experiment chambers. The basic idea of the design is the use of fixed mounted gratings of diffent radii and groove densities and a big two-dimensional position sensitive detector mounted on a x-y angle table. The design is discussed in some detail and performance is presented.

Core level binding energies for the elements Hf to Bi (Z=72-83)

The binding energies of all core levels in the N and O shells for the elements Hf to Bi have been measured by means of electron spectroscopy. The binding energies obtained are compared to previously reported values.

A photoelectron spectroscopy and photon stimulated desorption study of H2O on Si(100) 2×1

We have studied H2O adsorption on the Si(100) surface using photoelectron spectroscopy to record Si valence bands and Si 2p core level spectra; and photon stimulated desorption to record Si 2p edge total electron yield and H+‐ion yield spectra. We assign the valence‐band H2O induced peaks at EB=6.3 and 11.2 eV to the Si–OH and to the O–H bonds, respectively. The H2O dosed Si 2p core level spectrum exhibits two H2O induced equal intensity surface peaks with surface core level shifts of +0.25 and +1.00 eV that we assign to surface Si atoms in the Si–H and the Si–OH bonds, respectively. We interpret the features in the Si 2p edge H+‐ion yield spectrum as ion desorption from SiO2 at surface defect minority sites. We conclude that H2O adsorbs dissociatively as H and OH radicals on the Si(100) 2×1 surface dimers and that there are defect minority sites on the surface where H2O adsorption causes SiO2 formation.

An yttrium Mξ source for ESCA

Abstract A new source for producing YMξ radiation in an ESCA spectrometer is described. The system makes use of continuous evaporation of yttrium on a rotating anode. It is demonstrated that this scheme allows YMξ-excited electron spectra to be recorded without gradual loss of resolution and intensity due to anode oxidation. Electron spectra of Ar, Hg and N 2 excited by YMξ radiation are studied. Relative photoelectric cross-sections of the 5d 5 2 , 5d 5 2 and 6s orbitals in Hg and the four valence orbitals in N 2 are measured. The valence electron shake-up spectrum of N 2 is discussed.

Surface and bulk core level binding energy shifts in PtAu alloys

The surface core level shift of the 4f72 level in a Pt2%Au and a Pt15%Au alloy has been investigated using high resolution synchrotron radiation excited photoelectron spectroscopy. The bulk and surface components in the recorded spectra have been extracted using a curve fitting procedure. The chemical shifts and the bulk-to-surface intensity ratios are consistent with a strong enrichments of Au to the alloy surfaces. The chemical shifts on nonsegregated surfaces have been measured on these alloys and on a Pt90%Au alloy using conventional XPS.

Evidence for N2N3N45 super coster kronig processes in metallic Nb, Mo, Ru and Rh

The 4p photoelectron spectra of metallic Nb, Mo, Ru and Rh have been recorded. By use of a deconvolution procedure it is shown that the 4p12 spin-orbit component has a linewidth which significantly exceeds that of the 4p32 component. This suggests that N2N3N45 super Coster Kronig processes give a considerable contribution to the decay rata of the 4p12 hole state.