| 1. |
- Punkkinen, M. P. J., et al.
(författare)
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Surface core-level shifts of GaAs(100)(2x4) from first principles
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:11
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations show that measured surface core-level shifts (SCLSs) of the GaAs(100)(2x4) surfaces can be described within the initial state effects. The calculated As 3d and Ga 3d SCLSs for the beta 2 and alpha 2 reconstructions of the GaAs(100)(2x4) surfaces are in reasonable agreement with recent measurements. In particular, the results confirm that both the lower and the higher binding energy SCLSs, relative to the bulk emission in the As 3d photoelectron spectra, are intrinsic properties of the GaAs(100)(2x4) surfaces. The most positive and most negative As shifts are attributed to the third layer As atoms, which differs from the previous intuitive suggestions. In general, calculations show that significant SCLSs arise from deep layers, and that there are more than two SCLSs. Our previously measured As 3d spectra are fitted afresh using the calculated SCLSs. The intensity ratios of the SCLSs, obtained from the fits, show that as the heating temperature of the GaAs(100)(2x4) surface is increased gradually, the area of the alpha 2 reconstruction increases on the surface, but the beta 2 phase remains within the whole temperature range, in agreement with previous experimental findings. Our results show that the combination of the experimental and theoretical results is a prerequisite for the accurate analysis of the SCLSs of the complex reconstructed surfaces.
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| 2. |
- Laukkanen, P., et al.
(författare)
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A comparative study of clean and Bi-stabilized InP(100)(2 x 4) surfaces by the core-level photoelectron spectroscopy
- 2007
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 601, s. 3395-
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Tidskriftsartikel (refereegranskat)abstract
- The bismuth-stabilized (2 x 4)-reconstructed InP(100) surface [Bi/InP(100)(2 x 4)] has been studied by synchrotron-radiation core-level photoelectron spectroscopy. The spectra are compared with previous core-level data obtained on a clean InP(100)(2 x 4) surface. The findings support that the P 2p surface-core-level shift (SCLS) of the clean InP(100)(2 x 4), which has higher kinetic energy than the bulk emission, arises from the third-layer P atoms and that the second P 2p SCLS, which has lower kinetic energy than the bulk, arises from the top-layer P atoms. Similar In 4d SCLSs are found on the clean and Bi-stabilized InP(100)(2 x 4) surfaces, indicating that these shifts contain contributions of the In atoms that lie in the second and/or fourth layers. In addition to this, the results improve our understanding of the atomic structure of the Bi/InP(100)(2 x 4) surface and lead to refined surface models which include Bi-Bi and Bi-P dimers. (C) 2007 Elsevier B.V. All rights reserved.
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| 3. |
- Kuzmin, M., et al.
(författare)
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Atomic and electronic structure of the Yb/Ge(111)-(3x2) surface studied by high-resolution photoelectron spectroscopy
- 2007
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 75
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Tidskriftsartikel (refereegranskat)abstract
- Using high-resolution synchrotron-radiation photoelectron spectroscopy and low-energy electron diffraction, we have studied the electronic and structural properties of the Yb-induced Ge(111)-(3x2) reconstruction with a 1/6 monolayer coverage. We found these properties to be similar in many respects to those of the metal-induced Si(111) and Ge(111) reconstructions described previously in terms of the honeycomb chain-channel (HCC) structure. In particular, the Yb/Ge(111)-(3x2) is revealed to have a semiconducting character, the Yb atoms are divalent, and the surface states observed for the Yb/Ge(111) closely resemble those of the Na/Ge(111)-(3x1) in the literature. The Ge 3d core-level analysis, however, shows that the Ge 3d spectra from Yb/Ge(111)-(3x2) drastically differ from corresponding spectra of other Si and Ge HCC reconstructions. An atomic model, based on the general HCC geometry, is proposed for the Yb/Ge(111)-(3x2) surface. In this model, the important structural aspects are a buckling of the Ge = Ge double bond in the top, HCC-reconstructed layer plus a strong rearrangement of the second-layer atoms.
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