| 1. |
- Johansson, H. I P, et al.
(författare)
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Core-level shifts on Be(101̄0)
- 1994
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Ingår i: Physical Review B (Condensed Matter). - 0163-1829. ; 49:24, s. 17460-17463
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Tidskriftsartikel (refereegranskat)abstract
- A high-resolution photoemission study of the Be (101̄0) surface, at a sample temperature of 100 K, is reported. Three surface-shifted Be 1s components are revealed having shifts of -700, -500, and -220 meV. These are interpreted as originating from the first, second, and third plus fourth atomic layers while the bulk signal originates from the fifth and deeper layers. The surface layer shift for this more open Be(101̄0) surface is found to be smaller than for the close-packed Be(0001) surface. Reasons for this unusual behavior are suggested.
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| 2. |
- Johansson, L. I., et al.
(författare)
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Surface core level shift on Be( 112̄0)
- 1994
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 321:3
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Tidskriftsartikel (refereegranskat)abstract
- A photoemission study of the Be(112̄0) surface carried out at a sample temperature of 100 K is reported. A surface shifted Be 1s component, having a shift of - 410 meV, is resolved on this surface. The extracted surface to bulk intensity ratio indicate that this component originates from atoms in the surface layer only. This is opposite to previous observations on both the close-packed Be(0001) surface and the Be(101̄0) surface where sub-surface shifted Be 1s levels were unambiguously identified. Among these three surfaces a surface layer atom is expected to have the lowest coordination on the (112̄0) surface but the surface layer shift is found to be smallest on this surface. Compared to findings on other metals this is unusual and reasons contributing to this behaviour are suggested and discussed.
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| 3. |
- Johansson, L. I., et al.
(författare)
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Three surface-shifted core levels on Be(0001)
- 1993
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Ingår i: Physical Review Letters. - 0031-9007. ; 71:15, s. 2453-2456
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Tidskriftsartikel (refereegranskat)abstract
- The results of a high resolution photoemission study of the Be(0001) surface carried out at temperatures between 100 and 450 K are reported. At 100 K, three distinctly shifted Be 1s levels, exhibiting shifts of -825, -570, and -265 meV, are revealed and interpreted to originate from the three outermost atomic layers. Identification of two subsurface core level shifts and a first layer surface shift of -825 meV is unique among close-packed metal surfaces. Temperature dependent broadening effects observed in the bulk and surface BE 1s peaks are also reported.
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| 4. |
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| 5. |
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| 6. |
- Qvarford, M., et al.
(författare)
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Polarisation-dependent X-ray absorption in high- and low-Tc Bi2Sr2Can-1CunO4+2n superconductors
- 1993
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Ingår i: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 214:1-2, s. 119-126
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Tidskriftsartikel (refereegranskat)abstract
- Taking advantage of the linear polarisation of synchrotron radiation, the polarisation dependence of the O K and Cu L3 X-ray absorption edges has been compared for in situ cleaved Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 single crystals. The X-ray absorption spectra were measured by means of total electron yield detection. The spectra show for both crystals that the lowest unoccupied Cu 3d and O 2p orbitals are dominantly oriented parallel to the a-b plane, but also the presence of a small amount of unoccupied orbitals oriented perpendicular to the a-b plane can be deduced from both the O K and Cu L3 absorption spectra. A shift of the order of 0.5 eV between absorption into the in-plane and the out-of-plane Cu 3d orbitals was measured for the Bi2Sr2CaCu2O8 crystal, but no such shift was found for the Bi2Sr2CuO6 crystal.
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| 7. |
- QVARFORD, M, et al.
(författare)
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X-RAY-ABSORPTION AND RESONANT-PHOTOEMISSION STUDY OF CA IN THE HIGH-TEMPERATURE SUPERCONDUCTOR BI2SR2CACU2O8
- 1992
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 46:21, s. 14126-14133
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Tidskriftsartikel (refereegranskat)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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