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In our paper(1) the N 1s core level energy as obtained by Al Kα excited X-ray photoelectron spectroscopy (XPS) of boron nitride on Ru(0001) is not correctly reproduced, it is 398.63 ± 0.15 eV and not 389.63 ± 0.15 eV. Table 1 reproduces the B 1s and N 1s binding energies and work functions for h-BN on Rh(111), Ru(0001), Ni(111), and Pd(111).(2)Figure 1 reproduces the corresponding core level data with the correct energy scale. We are grateful to W. Auwarter for spotting these inconsistencies.

The structural sensitivity of x-ray photoelectron diffraction is greatly enhanced by the acquisition of a full hemispherical diffraction pattern of chemically shifted core levels. Complex systems can be studied resolving the local order per element and per chemical environment. This technique is applied to study the earliest stages of hydrogenated diamondlike carbon film deposition on Si(001). Effects of the sample temperature and ion dose on the structure of deposited layers are discussed.

X-ray photoelectron diffraction has been used to investigate the interfaces of Ni/diamond, Si/diamond and Au/diamond. These elements were evaporated in UHV on doped and undoped diamond (100) and (111) substrates at different temperatures. While Ni grows heteroepitaxially on the diamond surface no orientation was observed for Si and Au. The Si/diamond interface shows no carbide formation even when heating to 850 °C. However, the C 1s peak of the diamond substrate shifts to lower binding energy when evaporating Si. This could possibly be explained by band bending at the interface. Ni, Si and Au form islands at these low film coverages.

Natural diamond (001) and (111) surfaces as well as highly oriented pyrolithic graphite (HOPG) (0001) have been analyzed by X-ray induced photoelectron diffraction (XPD). The measured 2π patterns of C Is emission (964 and 1450 eV) and of KVV Auger emission (260 eV) are compared to single scattering cluster (SCC calculations, and excellent agreement is found. The comparisons show that photoelectron forward focusing is much less prominent in carbon solids than in all previously studied, heavier elements, and a direct interpretation of the data is therefore more difficult. The highly textured nature of HOPG presents itself as a circular pattern with concentric rings centered at the surface normal ( c -axis). The aim of this work is to show the advantage of the XPD technique as a diagnostic tool for the investigation of epitaxial diamond growth with monolayer sensitivity.

High resolution angle resolved photoemission spectra from potassium adsorbed on a single-domain Si(100)2 × 1 surface show K-derived states near the Fermi level. The metallization occurs when half a monolayer of K is deposited and a maximum decrease in the work function is observed. At slightly lower K coverage, the surface is still semiconducting. The metallic K-derived state presents non-parabolic-like dispersions in the directions along and perpendicular to the dimer rows, showing a behavior rather different to the one observed for alkali adsorption on metals.

The dissolution of Pt/Cu(111) and the kinetic blocking of the dissolution process which results in the formation of a surface alloy have been studied. We use AES, PES, XPD, and LEED to characterise the non-classical dissolution behaviour. Chemical shifts on the Pt 4f72 and the Cu 3p core levels are measured during dissolution. The top layer of the surface alloy is Cu3Pt for an annealing temperature of 315°C. For the higher annealing temperature of 350°C the Pt concentration is smaller. The alloy composition is therefore temperature dependent and the formation of a relatively stable alloy in local equilibrium over the surface layers is determined by the segregation and ordering behaviour. The chemical ordering of the surface alloy and its electronic structure remains to be verified.

Auger data shows a layer by layer growth of Pt/Cu(111) for the first three monolayers at room temperature. Surface core level photoemission spectroscopy using synchrotron radiation confirms the Auger analysis. Furthermore decomposition of the Pt4f 7/2 level permits quantification of the emission from the surface and interface atoms. Surface mobility of the Pt may also be inferred, coalescence of the surface layer occurs for coverages greater than 0.5 ML. XPD results confirm that the Pt grows with an fcc structure. An analysis of the anisotropies of the forward scattering peaks confirms the layer by layer growth model.

We have carried out a combined X-ray photoelectron diffraction (XPD) and low-energy electron diffraction (LEED) study of the interaction of oxygen with Ni(001) at ambient temperature from the c(2 × 2) structure up to the saturated oxide. Several structural conclusions are possible based on an R-factor comparison of an extensive series of azimuthal- and polar-O 1s XPD data to theoretical simulations based on a single-scattering cluster (SSC) model with spherical wave scattering. A new method for normalizing experimental and theoretical intensities for XPD R-factor analyses is also used. For the c(2 × 2) structure, we find that the oxygen sits in the fourfold hollows site, at a vertical distance (z) of approximately 0.75 A above the first Ni plane, in excellent agreement with the most recent LEED determination. There is also strong evidence from the XPD results that oxide nucleation occurs very early in the chemisorption region (much earlier than observable by LEED) and this effect could explain the proposals for in-plane bonding or pseudobridge bonding previously reported in the literature. The saturated oxide that forms at ambient temperatures is found from LEED and XPD to form a strained superlattice that is expanded by 1 6 with respect to the underlying Ni(001). We also find that the saturation oxide coverage is much larger than that previously reported in the literature of 2–3 monolayers (ML), and that it is in fact 4–5 ML. Other conclusions concerning the nature of the strain in the oxide are also possible, including a vertical expansion in lattice constant from the first to second plane of 0.1–0.2 A.

Ultrathin films of one monolayer (ML) or less of Au on Cu(001) have been prepared by in situ deposition at 300 K in order to investigate the formation of a surface alloy. The local order within these films was determined by X-ray photoelectron diffraction, measuring full solid angle Au4d 5 2 intensity distributions. For deposition of between 0.2 and 0.6 Ml we confirm that a surface alloy is formed, with a mixed c(2 × 2) Au/Cu layer on top. In contrast to earlier low-energy electron diffraction measurements we find a measurable amount of substitutional Au in the 2nd and 3rd layer. At a coverage of 1.2 ML all azimuthal structure in the angular distribution is lost, consistent with the growth of an incommensurate pseudo-hexagonal Au overlayer with no short-range orientational order. Still the presence of narrow rings of higher intensity reveals the presence of subsurface Au.

A method for a controlled change of the doping level of high-temperature superconductors with ultraviolet radiation is presented. With photoemission it is shown that the exposure of Bi2Sr2CaCu2O8+δ samples to the light of a He gas-discharge lamp causes oxygen desorption. From measurements of the Fermi surface, it is found that the oxygen desorption causes a decrease of the doping level of the superconductors. From the desorption cross sections that strongly depend on the photon energy, two different oxygen desorption channels are inferred. This procedure for decreasing the doping level has the advantage that the crystallinity of the sample is not altered and that the doping level can be simultaneously measured by photoelectron spectroscopy.

The local structure of p(2×2)-Na/Al(111) has been investigated using angle-scanned full hemispherical x-ray photoelectron diffraction. The resulting diffraction patterns allow a direct and unequivocal determination of the surface atomic structure. Even though Na and Al are completely immiscible in the bulk, the p(2×2)-Na/Al(111) phase consists of a composite double-layer surface alloy where Na atoms take substitutional and fcc hollow sites and Al atoms removed from the surface occupy hcp hollow sites.

Multiple-scattering (MS) calculations are presented for polar intensity scans of Mg Kα excited A12s emission from linear atomic Al chains, and compared to corresponding scans of Cu LVV Auger emission from linear Cu chains. Such model calculations permit an assessment of the importance of multiple-scattering effects in substrate emission along low-index directions. Intensity reductions in forward scattering due to MS defocusing effects are seen for both Al and Cu. However, for Al they are found to be significantly slower in turning on with distance along the chain. A systematic investigation revealed that this difference between Al and Cu is caused by their different scattering potentials. This material dependence should be important in analyzing such diffraction data in a quantitative way.

On observe des anisotropies du photocourant de 73% et 65% dans des balayages azimuthaux des intensites des niveaux de cœur 1s et 2s comprenant la direction [011]. De plus on mesure les pics de perte des plasmons accompagnant les raies de cœur 2s

Azimuthal X-ray photoelectron diffraction (APD) experiments have been carried out on a sample of Hg0.78Cd0.22 Te (MCT) epitaxially grown by liquid phase epitaxy (LPE) on (111) CdTe. To our knowledge this is the first XPD study of the (111) face of a II-VI semiconductor. Reproducible diffraction features are seen for emission from core levels of Hg, Cd and Te both before and after minimum ion bombardment, with bombardment being done to remove the native oxide overlayer. Single scattering cluster (SSC) calculations have been carried out using a spherical wave (SW) model. From comparison between experiment and theory an absolute determination of the surface polarity is possible.

We present a new method to study the formation of a metallic film on an insulator. During the deposition of a metal on an insulator we measure the capacitance C(t) of the forming metal insulator structure and monitor the metal deposition rate with a quartz-crystal microbalance. Ce was deposited with rates of around 4 ML min −1 on a thermally, dry-grown, SiO 2 layer on a Si substrate. From the C(t) curve of the forming metal-insulator-semiconductor (MIS) structure we can distinguish three stages of the Ce film growth. Up to 3 ML of Ce no capacitance change is observed. In the second stage, between 3 and 5 ML, a steep increase of the capacitance occurs. From 5 to 10 ML the capacitance saturates gradually to the maximum value. At coverages which correspond to the first stage, Ce diffusion into SiO 2 was observed with X-ray photoelectron spectroscopy (XPS). The analysis of the Si(2s), O(1s) and Ce(3d) core levels suggest a Ce diffusion into oxygen vacancy positions of SiO 2− δ at room temperature.

The surface polarity of a mercury cadmium telluride (MCT) (111) crystal surface has been determined by x‐ray photoelectron diffraction (XPD). Emission from the core levels of Hg, Cd, and Te gave reproducible photoelectron diffraction patterns with considerable fine structure. Comparisons between experiment and single scattering cluster calculations via R factors very well distinguished the different kinds of lattice site of Cd, Hg, and Te, and also permitted unambiguously assigning a cationic termination to the sample studied. This is thus a demonstration of the capability of XPD to study the type of termination involved at MCT and other compound semiconductor surfaces.

Photoemission (UPS) and inverse photoemission (BIS) spectra of NiO grown as a thin film on metallic Ni are reported. The data are discussed with respect to the electronic structure of the occupied and empty states in NiO.

We have analyzed the valence band region and the 3d core levels of Ce, CeH2.1 and CeH2.9 by means of X-ray photoelectron spectroscopy. Hydrogen induced states appear about 5 eV below EF. The density of states at EF is about 4 times smaller in CeH2.1 than in Ce and vanishes completely in CeH2.9 in agreement with the metal to semiconductor transition which was observed in resistivity measurements. The 4f level is well split off the hydrogen induced band at 2 eV for both hydrides. The 3d core levels are shifted by 1.9 and 2.1 eV from Ce to CeH2.1 and CeH2.9, resp., and exhibit intense satellites on the low BE side. A simple method to prepare large, compact samples of rare earth hydrides is described.

We analysed the valence band and the 3d and 4d core levels of LaH x ( x = 0, 2.2, 2.9) and CeH x ( x = 0, 2.1, 2.9) using X-ray photoelectron spectroscopy. A hydrogen-induced band around 5 eV is observed in all the hydrides. The density of states at E F is considerably reduced in the dihydrides and vanishes completely in the trihydrides in agreement with the transition from metallic to non-metallic behaviour. The cerium 4f level appears at 2 eV and is separated from the hydrogen-induced band for both cerium hydrides. The character and occupancy of the 4f levels of cerium is almost conserved in the hydrides as is confirmed by measurements of the magnetic susceptibility. The 3d core levels are shifted by 1.3 eV (LaH 2.2 ), 2.9 eV (LaH 2.9 ), 1.9 eV (CeH 2.1 ) and 2.1 eV (CeH 2.9 ) and exhibit intense satellites on the low binding energy side.

The magnetic properties of CeH x were investigated in the concentration range 1.8 x ⩾ 3.0. Susceptibility measurements from 300 K down to 1.3 K show different effective magneton numbers per cerium ion for different hydrogen concentrations. Deviations from Curie-Weiss behaviour due to crystal field effects are observed. The a.c. susceptibility data reveal distinct maxima at 4.2 K and 2.4 K for CeH 2.43 and CeH 3.00 respectively. We determined the type and structure of the magnetic order by means of high field magnetization measurements and neutron diffraction experiments. CeH 2.43 orders ferromagnetically, whereas CeD 3.0 shows an antiferromagnetic alignment of moments of 0.64 (7) μ B along the [111] direction.

On recrystallized Eu2O3 we have measured the optical re-emission which is very sensitive to Eu2+ contamination. On this material we observed XPS core level and valence band spectra. Only Eu3+ peaks could be identified, thus neither in the bulk nor at the surface Eu2+ is stable. We conclude that neither shake down effects nor intermediate valence is present in Eu2O3.

The saturated oxide formed on Ni(001) under UHV conditions has been studied by x-ray photoelectron diffraction (XPD) and low-energy electron diffraction. At ambient temperature and with a 1200-L exposure to oxygen, the saturation oxygen coverage is found to be 4.3\ifmmode\pm\else\textpm\fi{}0.4 monolayers (ML) as measured relative to the Ni(001) surface-atom density. [1 langmuir (L)${==10}^{\mathrm{\ensuremath{-}}6}$ Torr sec.] The oxide is furthermore found to grow primarily as NiO(001) in a highly strained superlattice for which the horizontal lattice constant is expanded by (1/6 compared to the underlying Ni(001). The XPD results are found to be very sensitive to the degree of short-range order in the oxide before and after light annealing, particularly when obtained with high angular resolutions of approximately \ifmmode\pm\else\textpm\fi{}1.0\ifmmode^\circ\else\textdegree\fi{}. Single-scattering calculations with spherical-wave scattering are found to give an excellent description of the XPD from the annealed and more-ordered overlayer. These results also suggest the general utility of high-resolution XPD for studying the degree of short-range positional order present in epitaxial overlayers.