R. Cosso

Angle-resolved photoemission from an unusual quasi-one-dimensional metallic system: a single domain Au-induced 5 × 2 reconstruction of Si(111)

Angle-resolved photoemission spectroscopy (ARPES), using HeI radiation, has been used to probe the occupied electronic states from a single domain of the Au-induced 5 x 2 reconstruction of Si(lll), a quasi-one-dimensional (quasi-1D) metallic system. The ARPES spectra recorded parallel (perpendicular) to the Au chain structure show a signature of a metallic (non-metallic) system. These experimental results are intriguing since, for the first time, spectral intensity at the Fermi level is observed in a photoemission study of a quasi-1D metallic system.

Charge-Transfer Satellites in K L23 XAS Data for K/Si(111)-(2 × 1): Evidence for Strong Ionic Bonds

We report K L23 edge X-ray absorption spectra (XAS, both normal and grazing incidence) and photoelectron spectra (XPS) for K/Si(111)-(2 × 1) at three different coverages (0.1, 0.3 and 0.5 ML). The data show features which exhibit a very strong variation in both the energy, intensity, and line shape with incidence angle and coverage. Some of these features correspond to charge-transfer satellites and give a measure of the hybridization of the ground state. They indicate very ionic bonding.

Experimental and theoretical study of the PL2,3VV Auger lineshape of GaP(110)

Abstract A joint experimental and theoretical investigation of the PL 2.3 VV Auger transition on GaP(110) is presented. The theoretical data, calculated within a pure band-like picture, are compared to the experimental spectra. The angular momentum character of the five features constituting the lineshape is identified. Strong contributions to the experimental data from many-body effects may be ruled out due to the good overall agreement with the theoretical lineshape therefore supporting a single particle description for this Auger feature. We discuss effects such as Coulomb correlation, initial state core hole screening, self-energy corrections, that may possibly contribute to the relative energy shifts observed in one of the pp components of the compared spectra.

Surface structure of rare earth metals

Abstract We have performed LEED, angle-resolved UV photoemission (ARUPS) and inverse photoemission (IPE) measurements on a representative set of hcp rare earth surfaces in order to obtain basic structural information. LEED patterns from the (0001) surfaces show six-fold symmetry due to the two equally probable bulk terminations. ARUPS data show a large non-dispersing peak at ~ 10 eV binding energy, with intensity extremely sensitive to surface order, which is not reproduced in one-electron calculations. Suggestions that this many-body feature is due to an unoccupied surface state are supported by our IPE data, which appear to show such a state just above the Fermi level. LEED patterns from the (1120) surfaces of Y. Ho and Er also show six-fold symmetry, with no visible substrate spots, implying that these relatively open surfaces have collapsed to a (7 × 1) close-packed structure many layers deep. ARUPS data from the reconstructed (1120) surface of Ho are virtually indistinguishable from those obtained from Ho(0001). This suggests that the two structures are identical within the probing depth of this technique.

Experimental and theoretical surface component of the PL2,3VV Auger lineshape in GaP(110): the use of ordered (1 × 1) Sb overlayers

Abstract An analysis of the theoretical and experimental surface contribution of the PL 2,3 VV Auger lineshape in GaP(110) is performed. From the theoretical point of view the lineshapes are calculated within a single-particle framework from a slab-by-slab tight-binding calculation of the ideal and real relaxed surfaces. The experimental information is extracted by comparing the Auger feature of as-cleaved GaP(110) and of the GaP(110) interfaced with one ordered monolayer of Sb. This allows the LVV surface component to be isolated. A comparison with theory, showing strong similarities in the position of the surface-related features is discussed.

Surface electronic structure of rare earth metals

Abstract Angle-resolved UV photoemission has been used to investigate the electronic structure of the (0001) surfaces of scandium, yttrium, praseodymium and gadolinium. Off-normal emission spectra were recorded with high angular resolution, enabling detailed mapping of the dispersion of valence band features. Yttrium and gadolinium show similar results to published data from Ho(0001), suggesting minimal 4f influence in the lanthanide bandstructures. Differences seen on praseodymium and scandium may be due to 4f derived states and surface states respectively.

Erratum to “Angle-resolved photoemission from an unusual quasi-one-dimensional metallic system: a single domain Au-induced 5 × 2 reconstruction of Si(111)” [Surface Science 325 (1995) 45]

Note: Univ liverpool,interdisciplinary res ctr surface sci,liverpool l69 3bx,merseyside,england. univ dublin trinity coll,dept pure & appl phys,dublin 2,ireland. ecole polytech fed lausanne,inst phys appl,ch-1015 lausanne,switzerland. univ liverpool,dept phys,liverpool l69 3bx,merseyside,england.ISI Document Delivery No.: RQ630 Reference LSE-ARTICLE-1995-006doi:10.1016/0039-6028(95)00438-6View record in Web of Science Record created on 2006-10-03, modified on 2017-05-12

ELECTRON-ENERGY LOSS AND AUGER-SPECTROSCOPY OF THE YB-GAP(110) INTERFACE

Abstract The Yb GaP(110) interface formation was studied by EELS (electron energy loss spectroscopy) and AES (Auger electron spectroscopy). The EELS was performed in the 2–27 eV loss range at different coverages ranging from 0.5 to 20 ML (monolayer) with a primary beam energy of 100 eV. Losses typical of the interface were found at ∼ 35 and 6 eV. The EEL data are characterized by the persistence of the 20 eV loss associated with the Ga 3d level. The AES P L2,3VV data were taken at 1 and 2 ML as a function of the take-off angle. Lineshape changes were observed both versus coverage and versus angle, allowing insight into the bonding at the P site versus coverage and depth. A model of the morphology of the interface during the growth process is presented characterized by Yb P compounds formation and Ga segregation at the surface.

Surface local density of states of InP(110) via PL2.3VV Auger lineshape: the role of an ordered (1×1) Sb overlayer

Abstract An experimental and theoretical investigation on the PL 2.3 VV Auger lineshape of the InP(110) surface is presented. A band-like picture provides a good description of the spectral features. In addition, deposition of one monolayer of Sb on InP(110) is shown to drive the surface atoms into an environment similar to that present in the bulk, so that a comparison between the PL 2.3 VV spectrum from the clean and Sb-covered sample allows us to discriminate between the surface contribution and the bulk contribution to this surface-sensitive Auger transition.

An investigation of the unoccupied p-symmetry states in Ag- and Pd-containing systems via l→(l−1) high resolution near-edge X-ray absorption spectroscopy

In this work, the first systematic study of the low-lying, unoccupied p-derived states in Pd- and Ag- containing systems is reported. Ag and Pd M 4.5 near-edge X-ray absorption spectroscopy measurements from bulk Ag and Pd binary alloys, namely Cu 50 Pd 50 , Cu 80 Pd 20 , Ag 50 Pd 50 and Ag 80 Pd 20 , and of the Ag/Si(111)2×1 interface were performed. Recent studies have indicated that this kind of spectroscopy can provide valuable information on the unoccupied p-projected density of states, via a 3d→5p dipole allowed transition