Electronic band structure of the Pt{100} surface (original) (raw)
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The Journal of Chemical Physics, 2007
The ͑1 ϫ 1͒ → quasihexagonal ͑HEX͒ phase transition on a clean Pt͑100͒ surface was investigated by monitoring the time evolution of the Pt4f 7/2 core level photoemission spectra. The spectral component originating from the atoms forming the ͑1 ϫ 1͒ metastable unreconstructed surface was found at −570± 20 meV with respect to the bulk peak. Ab initio calculations based on density functional theory confirmed the experimental assignment. At temperatures above 370 K, the ͑1 ϫ 1͒ phase irreversibly reverts to the more stable HEX phase, characterized by a surface core level shifted component at −185± 40 meV. By analyzing the intensity evolution of the core level components, measured at different temperatures in the range of 393-475 K, we determined the activation energy of the phase transformation, E = 0.76± 0.04 eV. This value is considerably lower than the one previously determined by means of low energy electron diffraction. Possible reasons for this discrepancy are discussed.
Surface electronic structure of Pt(110): comparison with Ni and Pd
Progress in Surface Science, 2003
The unoccupied electronic structure of Pt(1 1 0) was investigated by inverse photoemission. The results were compared with the data for Ni(1 1 0) and Pd(1 1 0) with particular emphasis on surface states. The surface states in the Y gap of Pt(1 1 0) are shifted upwards relative to Ni and Pd, as a consequence of the (1 · 2) missing-row reconstruction. In contrast, the surface state at X is only weakly affected, which indicates that it is essentially a one-dimensional state, localized on the densely-packed atomic chains on the Pt(1 1 0) surface.
Voltammetric and UHV characterisation of the (1×1) and reconstructed hex-R0.7° phases of Pt{100
Journal of Electroanalytical Chemistry, 1999
The voltammetry of the clean (1×1) and reconstructed hex-R0.7° phases of Pt{100} prepared in UHV are reported. By comparison with the UHV data, both phases may readily be prepared using a flame-annealing procedure so long as the conditions of sample cooling are precisely controlled. The well-ordered (1×1) phase may be formed by cooling in hydrogen. Back transfer to UHV of the hydrogen-cooled sample gave rise to a p(1×1) LEED pattern. These findings are in accordance with previous investigations [Attard and Price, Surf. Sci. 335 (1995) 63 and erratum; Al-Akl et al., J. Chem. Soc. Faraday Trans. 91 (1995) 3585; Sashikata et al., Langmuir 14 (1998) 2896; Tidswell et al., Phys. Rev. Lett. 71 (1993) 1601]. The voltammetry of the UHV-prepared hex-R0.7° phase can be obtained only after a flame-anneal treatment by cooling rapidly in a flow of inert gas such as argon in which oxygen has been rigorously excluded. In contrast to the hydrogen cooled Pt{100} electrode, subsequent LEED analysis of the argon cooled sample showed a reconstruction pattern similar, though not identical to one reported recently by Zei et al. for a partially deconstructed Pt{100} electrode. On the basis of these results it is suggested that the p(1×1) and hex-R0.7° phases of Pt{100} may be prepared under ambient conditions in an electrochemical cell. Although the potentials at which the reconstructed phase is stable are different from those reported by Zei and co-workers, the data do support their earlier results showing that the reconstructed phase of Pt{100} is stable when in contact with electrolyte solutions.
C_{60} on the Pt(111) surface: Structural tuning of electronic properties
Physical Review B, 2011
The structure and electronic properties of the (√ 13 × √ 13)R13.9 • and (2 √ 3 × 2 √ 3)R30 • ordered phases of C 60 on the Pt(111) surface are investigated using combined dynamic low-energy electron diffraction and density functional theory (DFT) calculations. The two phases have the same local adsorption structure, while they are predicted by DFT calculations to exhibit very different electronic structures due to their different inter-C 60 orientations and distances. This result demonstrates the structural tuning of electronic properties for molecular films or junctions composed of the same materials.
1984
Describing the binding energy of both d and s valence electrons within the LCAO formalism, and by including repulsive Born-Mayer type interactions, we study the structural stability of the reconstructed and unreconstructed Pt(ll0) surfaces. Our main result is that amongst the various models for the (1 x2) reconstruction the "Bonzel-Ferrer" model is unfavoured, while the "missing-row" model seems to be energetically degenerate with the unreconstructed surface. Our calculation predicts also a small surface concentration, which, however, has only a minor effect on the total energy of the system.
Femtosecond electron dynamics of image-potential states on clean and oxygen-covered Pt(111)
Physical Review B, 2001
We have investigated the lifetimes of image-potential states on the Pt͑111͒ surface with time-resolved two-photon photoemission and first-principles calculations. Electrons populating the first two image-potential states decay into bulk states after 26Ϯ7 and 62Ϯ7 fs, respectively. This is in agreement with results of theoretical calculations. Oxygen adsorption reduces the image-potential state lifetimes by a factor of 2. This is caused by a strong change of the electronic structure near the Fermi level.
Physical Review B, 1996
The Sm-on-Pt͑100͒ overlayer system has been studied by photoelectron spectroscopy, scanning tunneling microscopy ͑STM͒, and low-energy electron diffraction ͑LEED͒ at room temperature. As Sm overlayers were evaporated onto the Pt͑100͒-hex-R0.7°reconstructed single-crystal surface, the initial growth of the interface was studied. Photoelectron spectroscopy and LEED indicate that Sm and Pt has formed an intermixed, disordered phase in the surface. The Pt 4 f core-level spectra indicate the existence of an unresolved surface component that disappears with Sm deposition. For all Sm coverages ͑0.3-20 Å͒, trivalent Sm was observed. Some divalent Sm was seen after ϳ20 Å Sm deposition, and was believed to stem from Sm atoms at the surface. LEED and STM show that Sm adsorption induces a local lifting of the hexagonal reconstruction. The first monolayer of the Sm-Pt compound grows as long ͑100-1000 Å͒, narrow ͑30-50 Å͒ islands directed along the direction of longest periodicity of the reconstructed structure. At the same time, the uncovered areas display the hexagonally reconstructed structure. The Sm-Pt islands are seen to be centered on the elevated ridges of the reconstruction. There are no indications of preferential nucleation centers, such as steps or defects. Two effects are discussed to contribute simultaneously to the observed island shape: ͑1͒ an anisotropic Sm diffusion, favoring diffusion along the reconstruction ridges, and ͑2͒ lifting of the reconstruction along the elevated ridges is the energetically favorable process, due to lower Pt-Pt coordination in these on-top sites. ͓S0163-1829͑96͒04024-6͔
The Double Diffraction Model for LEED-Intensity Spectra of the Clean Pt(100) Surface
Zeitschrift für Naturforschung A, 1977
The intensity spectra of the superstructure diffraction spots of the clean platinum (100) surface are presented for normal or nearly normal incidence. Their gross features are interpreted in terms of multiple diffraction contributions. It is shown that most of the maxima in the spectra can be explained by double diffraction processes from an idealized pure hexagonal surface layer and quadratic bulk layers. Alternative models in which the surface layer exchanges already all occuring reciprocal lattice vectors would predict additional peaks which, however, do not arise. Therefore superstructure features of the surface layer are assumed to be of second order. Thus double diffraction involving only idealized hexagonal and quadratic structures seems to dominate the diffraction behaviour of clean Pt(100).