| 1. |
- Kuzmin, M., et al.
(författare)
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Yb-induced (2x3) and (2x4) reconstructions on Si(100) studied by first-principles calculations and high-resolution core-level photoelectron spectroscopy
- 2008
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 78:4
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Tidskriftsartikel (refereegranskat)abstract
- We report here a combined theoretical and experimental study of Yb/Si(100)-(2x3) and -(2x4) reconstructions by means of first-principles calculations and high-resolution core-level photoelectron spectroscopy. Energetically stable atomic structures are presented for these reconstructions. Yb atoms are found to occupy the cave sites in the structures, and the Si substrate is strongly rearranged due to Yb adsorption. It is shown that scanning tunneling microscopy images and surface core-level shifts (SCLSs) calculated for these atomic configurations agree with experimental data, giving further support to the models. In addition, by comparing our theoretical and experimental Si 2p results, we discuss and interpret the atomic origins of SCLSs measured for the YbSi(100)-(2x3)/(2x4). Finally, the results presented are helpful in the analysis of (2x3) and (2x4) structures induced by other rare earth metals on Si(100).
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| 2. |
- Feng, Lei, et al.
(författare)
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Designing communicating transaction processes by supervisory control theory
- 2007
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Ingår i: Formal methods in system design. - : Springer Science and Business Media LLC. - 0925-9856 .- 1572-8102. ; 30:2, s. 117-141
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Tidskriftsartikel (refereegranskat)abstract
- A Communicating Transaction Process (CTP) is a computational model that serves as a high level specification language for reactive embedded system components and their interactions. It consists of a network of communicating processes coordinating their behaviors via common actions and the common actions are refined as a set of guarded Message Sequence Charts (MSCs). There has been little work devoted to developing CTP models systematically. This paper takes the first step towards bridging this gap. In our work, communicating processes of embedded components are modeled and controlled as Discrete-Event Systems (DES). The control logic among communicating components is derived by Supervisory Control Theory (SCT), so as to guarantee that the communicating processes meet all predefined constraints and possess other desirable system behavioral properties. The control logic is then translated into propositional formulas for guarded MSCs which then results in a CTP model with guaranteed behavioral properties.
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| 3. |
- Joco, V., et al.
(författare)
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Surface phase transition and electronic structure of c(5 root 2 x root 2)R45 degrees-Pb/Cu(100)
- 2006
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Ingår i: Proceedings of the 23th European Conference on Surface Science (Surface Science). - : Elsevier BV. - 0039-6028. ; 600:18, s. 3851-3855
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Konferensbidrag (refereegranskat)abstract
- The c(5 root 2 x root 2)R45 degrees-Pb/Cu(100) surface phase is investigated by means of angle resolved ultraviolet photoemission and low energy electron diffraction in the temperature range between 300 and 550 K. We identify and characterize a temperature-induced surface phase transition at 440 K from the room temperature e(5 root 2 x root 2) R45 degrees phase to a (root 2 x root 2)R45 degrees structure with split superstructure spots. The phase transition is fully reversible and takes place before the two-dimensional melting of the structure at 520 K. The electronic structure of the split (root 2 x root 2)R45 degrees phase is characterized by a metallic free-electron like surface band. This surface band is backfolded with c(5 root 2 x root 2)R45 degrees periodicity phase at room temperature, giving rise to a surface band gap at the Fermi energy. We propose that a gain in electronic energy explains in part the stability of the c(5 root 2 x root 2)R45 degrees phase. (c) 2006 Elsevier B.V. All rights reserved.
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| 4. |
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| 5. |
- 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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| 6. |
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| 7. |
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| 8. |
- Martinez-Blanco, J, et al.
(författare)
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Surface phase diagram and temperature induced phase transitions of Sn/Cu(100)
- 2006
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Ingår i: Proceedings of the Eight International Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures and the Thirteenth International Congress on Thin Films - ACSIN8/ICTF13 (Applied Surface Science). - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 252:15, s. 5331-5334
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Konferensbidrag (refereegranskat)abstract
- Room temperature deposition of Sn on Cu(100) gives rise to a rich variety of surface reconstructions in the submonolayer coverage range. In this work, we report a detailed investigation on the phases appearing and their temperature stability range by using low-energy electron diffraction and surface X-ray diffraction. Previously reported reconstructions in the submonolayer range are p(2 x 2) (for 0.2 ML), p(2 x 6) (for 0.33 ML), (3 root 2 x root 2)R45 degrees (for 0.5 ML), and c(4 x 4) (for 0.65 ML). We find a new phase with a ((-4)(0) (2)(4)) structure for a coverage of 0.45 ML. Furthermore, we analyze the temperature stability of all phases. We find that two phases exhibit a temperature induced reversible phase transition: the (3 root 2 x root 2)R45 degrees phase becomes (root 2 x root 2)R45 degrees phase above 360 K, and the new ((-4)(0) (2)(4)) phase becomes p(2 x 2) also above 360 K. The origin of these two-phase transitions is discussed. (c) 2005 Elsevier B.V. All rights reserved.
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