A.P.J. Stampfl

Band structure of InGaAs

The valence‐band structure of unstrained In0.27Ga0.73As grown as a 4000‐A‐thick overlayer on GaAs, has been determined in the (001) direction from angle‐resolved photoemission data. The InGaAs bands lie between the bands of InAs and GaAs but the differences depend on k. The potential in the alloy is therefore not a simple average of that of the constituent compounds.

A medium-energy photoemission and ab-initio investigation of cubic yttria-stabilised zirconia

Experimental and theoretical investigations into the electronic properties and structure of cubic yttria-stabilized zirconia are presented. Medium-energy x-ray photoemission spectroscopy measurements have been carried out for material with a concentration of 8-9 mol. % yttria. Resonant photoemission spectra are obtained for a range of photon energies that traverse the L2 absorption edge for both zirconium and yttrium. Through correlation with results from density-functional theory (DFT) calculations, based on structural models proposed in the literature, we assign photoemission peaks appearing in the spectra to core lines and Auger transitions. An analysis of the core level features enables the identification of shifts in the core level energies due to different local chemical environments of the constituent atoms. In general, each core line feature can be decomposed into three contributions, with associated energy shifts. Their identification with results of DFT calculations carried out for proposed atomic structures, lends support to these structural models. The experimental results indicate a multi-atom resonant photoemission effect between nearest-neighbour oxygen and yttrium atoms. Near-edge x-ray absorption fine structure spectra for zirconium and yttrium are also presented, which correlate well with calculated Zr- and Y-4d electron partial density-of-states and with Auger electron peak area versus photon energy curve.

Low energy photoelectron diffraction analysis at high angular resolution of Cu and Mn/Cu surfaces

X-ray photoelectron diffraction simulations using a real-space approach are shown to accurately produce the extraordinarily detailed photoelectron diffraction pattern from Cu{111} at an electron kinetic energy of 523.5 eV. These same simulations show that most sensitivity is obtained when using low energy electrons at high angular resolution. Structural differences are observed to be greatest around a kinetic energy of ∼100 eV and many of the features observed in the photoelectron diffraction patterns may be directly related to phenomena observed in low energy electron diffraction patterns from the same surface. For Cu{100}, simulations of buckled surfaces with a Mn overlayer predict that low energy photoelectron diffraction can easily discriminate chemical and structural differences. Even the effects of the relaxed surface of Cu{100} is indeed observable along azimuthal scans around a kinetic energy of 100 eV. Our results show that low energy photoelectron diffraction is extremely sensitive to changes in...

Mapping the Fermi surface of Cu using ARUPS

Abstract The topology of the Fermi surface of copper has been illuminated in a direct fashion using the technique of photoelectron spectroscopy. Full emission hemisphere intensity distributions of photoelectrons excited from the Fermi energy by photons of various energies have been compared with the theoretically expected loci of such transitions and good agreement was found. An alternative method of determining the shape of a slice through the bulk Fermi surface involving the use of constant initial state spectroscopy has also been used for the first time. In particular, part of the Fermi surface of Cu in the ΓL[112] plane has been mapped in this way by following the k -space dispersion of transitions originating at the Fermi level as a function of photon energy.

Angle-resolved photoemission from a GaAs (1¯ 1¯ 1¯)-2×2 surface: Off-normal emission study

Angle-resolved photoemission experiments using synchrotron radiation have been performed on an As-rich GaAs(111)-2×2 surface over the photon energy range 10-70 eV. The occupied bulk and surface band structures of the surface were investigated using theoretical structure plots involving the linear-muffin-tin-orbital (LMTO) calculated initial bands and free-electron-like final states. Based on a three-step model, the calculations suggest that this surface is rich in surface umklapp effects and that many strong transitions may be explained as surface umklapp transitions involving mainly the surface reciprocal lattice vector g 2×2 =2π/a(-1/3,2/3,-1/3)