| 1. |
- Andersen, J. N., et al.
(author)
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Changes in the local surface geometry with conserved adsorbate coverage and long-range order caused by annealing
- 1992
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In: Physical Review B (Condensed Matter). - 0163-1829. ; 46:19, s. 12784-12787
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Journal article (peer-reviewed)abstract
- The ordered c(2×2) Na on Al(100) and (3 × 3) R30°K on Al(111) structures formed at either 100 K or at room temperature are studied by high-resolution core-level spectroscopy. For both systems equal alkali coverages are found at these two temperatures. The core-level spectra, however, show strong changes with temperature. This behavior leads to the surprising conclusion that annealing at room temperature causes an irreversible change in the local geometry, i.e., of the adsorption site, of the overlayer even though neither the long-range order nor the adsorbate coverage changes.
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| 2. |
- Andersen, J. N., et al.
(author)
-
Intermixing in the Na on Al(111) system
- 1992
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In: Physical Review Letters. - 0031-9007. ; 68:1, s. 94-97
-
Journal article (peer-reviewed)abstract
- Ordered structures formed by Na adsorption on the Al(111) surface are investigated by high-resolution core-level spectroscopy. It is shown that, contrary to the common picture of alkali adsorption, two of the structures formed at room temperature consist of intermixed Na-Al layers. The results for the (3 ×)-rotated-30°structure are also consistent with intermixing although they do not provide any definite proof. For Na layers deposited at 100 K no intermixing is found.
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| 3. |
- Nyholm, R., et al.
(author)
-
SYNCHROTRON-RADIATION SOFT-X-RAY PHOTOEMISSION-STUDY OF LEAD ON BI2CASR2CU2O8
- 1992
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In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 46:10, s. 6488-6494
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Journal article (peer-reviewed)abstract
- In this paper we present a study of the interaction of Pb with a clean single-crystal Bi2CaSr2Cu2O8 superconductor surface based on photoemission and low-energy electron diffraction (LEED). Deposition of Pb on a Bi2CaSr2Cu2O8 Crystal kept at room temperature gives rise to the formation of metallic Bi and oxidized Pb at the interface. This behavior could not be observed when the crystal was kept at 100 K during Pb deposition. For all investigated Pb overlayers on a cold crystal (100 K), surface-sensitive photoelectron spectroscopy revealed the growth of a covering metallic Pb overlayer film. The growth at 100 K, contrary to the growth at room temperature, preserved the original LEED 5 X 1 pattern even for Pb depositions corresponding to a 24-angstrom thick overlayer indicating epitaxial growth. Furthermore, a rigid 0.4-eV shift of the valence band and the Bi 5d core levels is observed upon initial Pb deposition and is tentatively attributed to electron doping.
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| 4. |
- Nyholm, R., et al.
(author)
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The surface core-level shift of the Pd(100) single-crystal surface
- 1992
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In: Journal of Physics: Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 4:1, s. 277-283
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Journal article (peer-reviewed)abstract
- The surface core-level shift of the Pd(100) single-crystal surface has been measured from high-resolution Pd 3d core-level spectra. The surface atoms are found to have 0.44+or-0.03 eV lower binding energy than the bulk atoms. The result is compared with theoretical estimates.
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| 5. |
- QVARFORD, M, et al.
(author)
-
X-RAY-ABSORPTION AND RESONANT-PHOTOEMISSION STUDY OF CA IN THE HIGH-TEMPERATURE SUPERCONDUCTOR BI2SR2CACU2O8
- 1992
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In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 46:21, s. 14126-14133
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Journal article (peer-reviewed)abstract
- The electronic structure of Ca in the high-temperature superconductor Bi2Sr2CaCu2O8 has been studied by x-ray-absorption spectroscopy and resonant-photoemission at the Ca L2,3 absorption edge. In the x-ray-absorption spectrum no edge structure is seen at the energy corresponding to the Ca 2p3/2 core-level binding energy, in agreement with the very low Ca density of states at the Fermi level predicted by band-structure calculations. Furthermore, the crystal-field splitting of the Ca 3d level, which is characteristic of ionic Ca compounds, is clearly observed in the x-ray-absorption spectrum. The photoemission spectra display strong resonant enhancements of the Ca 3s and 3p core levels as well as strong changes in the intensity and the line shape of the Ca L2,3M2,3M2,3 Auger structure at the Ca L2,3 threshold, showing the localized nature of the 3d states in core ionized Ca. The 3d induced spectator shift of the Ca L2,3M2,3M2,3 complex is fairly small as compared to what has been reported for CaF2, indicating that the screening of the normal Auger final state by the charge carriers in the surrounding Cu-O2 layers is quite efficient. From the Ca L2,3M2,3M2,3 data it is also suggested that, at the Ca L2 threshold, the excited 3d electron participates in a Coster-Kronig-type decay resulting in a 2p3/2 core hole followed by a normal L3M2,3M2,3 Auger decay.
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