STM and LEED observations of a c(2 × 2) Ge overlayer on Pt(1 0 0)

Matsumoto, Tetsuya; Batzill, Matthias; Koel, Bruce E.

doi:10.1016/j.susc.2009.04.028

Cited by 1 publication

(6 citation statements)

References 32 publications

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“…We note that the peaks in ALISS polar-angle scans for Pt scattering from Pt(100) surfaces with disordered Ge layers were close to those observed from the clean, reconstructed (5 × 20)-Pt(100) surface. This is consistent with the observation of (5 × 20)-Pt(100) domains using LEED and STM [12].…”

Section: Pt(100) Surfaces With Disordered Ge Layerssupporting

confidence: 92%

“…In STM and LEED studies reported in [12] we observed formation of a c(2 × 2) structure produced by deposition of 0.5 ML Ge on Pt(100) and annealing at 600 K. The outstanding question is whether this structure is due to a Ge overlayer or Ge incorporated into the surface as an alloyed layer; both structures are shown in figure 1. In both the surface alloy and the overlayer models, the lattice distance along the [010] long-bridge azimuth is the same (shown as A1-A4 in figure 1).…”

Section: Alissmentioning

confidence: 88%

“…Characterization of these surfaces by STM and LEED, as reported in [12] can be summarized as follows. STM images showed disordered Ge domains with Pt adislands at 0.2 ML/600 K and 0.5 ML/1200 K, c(2 × 2)-Ge layers at 0.5 ML/600 K, and porous incomplete c(2 × 2)-Ge layers at 0.5 ML/900 K. The c(2 × 2) LEED spots were found at 0.5 ML/600 K, 1.5 ML/600 K, and 1.5 ML/900 K, and sharpened most at 0.5 ML/600 K and 1.5 ML/900 K. Faint (1 × 1) spots were present at 0.2 ML/600 K and 0.5 ML/1200 K. Weak (5 × 20) spots remained at 0.2 ML/900 K and 0.2 ML/1200 K. No LEED pattern was observed at 1.5 ML/300 K or 4 ML/300 K.…”

Section: Stm and Leedmentioning

confidence: 99%

“…Negative CLSs of both Ge 3d and Pt 4f 7/2 peaks were found for surfaces with low Ge coverages compared to all other situations and pure Pt(100) and Ge(100). This derives from the greater screening that results from more Pt 5d electrons because of the lower hybridization per Pt atom and the increased number of surface Pt atoms that are present for rough surfaces with Pt adislands (at a density of 0.2 ML) in Ge domains (see figures 2, 3, 6 and 7 in [12]). The electron density in d-bands of surface atoms is higher than that in bulk atoms because the lower coordination narrows the valence d-bands upon formation of localized d-states below the Fermi level and transfers electrons from the bulk [51,53,54].…”

Section: Chemical State Information From Xpsmentioning

confidence: 99%

“…For Ge deposition on a Pt(100) surface, STM and LEED studies identified that an ordered c(2 × 2) structure could be formed at 0.5-ML Ge and below [11]. However, without a full I -V analysis of the LEED spots it was not possible to conclusively distinguish between a Ge overlayer (adlayer) and a surface alloy (incorporated or intermixed Ge-Pt topmost layer) from the surface corrugation of the STM topographs [12] or LEED pattern. The chemical reactivity of modifiers at surfaces strongly depends on whether the modifier is present in an overlayer or incorporated into the surface plane in an alloyed layer.…”

Section: Introductionmentioning

confidence: 99%

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Ge overlayer and surface alloy structures on Pt(100) studied using alkali ion scattering spectroscopy, x-ray photoelectron spectroscopy and x-ray photoelectron diffraction

Matsumoto¹,

Ho²,

Batzill³

et al. 2014

J. Phys.: Condens. Matter

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We have investigated surface structures formed by deposition of Ge on a Pt(100) substrate by using a multi-technique approach utilizing alkali ion scattering spectroscopy (ALISS), x-ray photoelectron spectroscopy (XPS), and x-ray photoelectron diffraction (XPD). ALISS was used to distinguish Ge overlayers from incorporated alloy layers for the surface structures reported, and to supply structural information about the surface alloy or 'layer compound' formed by the deposition of 1.5-ML Ge. A Ge adlayer forms following the deposition of 0.2-ML Ge on Pt(100) and annealing at 600 K. ALISS revealed that Ge adatoms in these overlayers had 1D (incomplete c(2 × 2)) Ge-Ge ordering along [010] and equivalent directions, even though this was not directly apparent in observations using LEED and STM. A c(2 × 2)-Ge overlayer was produced after 0.5 ML-Ge deposition on Pt(100) and annealing at 600 K. Deposition of 1.5-ML Ge on Pt(100) and annealing at 600 K caused extensive Ge interdiffusion into the third (subsurface) layer, while the first and second layers remained as a c(2 × 2) Ge overlayer and (1 × 1) Pt layer, respectively. We propose that the Pt(100) substrate thus is 'capped' by an alloy film with the structure of a body-centered tetragonal Pt2Ge layer compound, which is terminated by a pure-Ge layer that is indistinguishable from a c(2 × 2)-Ge adlayer. This explains the apparently 'strange' result that even though extensive Ge interdiffusion was occurring deeply into the Pt bulk during annealing at 900 and 1200 K, a Ge overlayer remained on the surface. XPS spectra showed a +0.5 eV binding energy shift of the Ge 3d core level and a small (0-0.1 eV) positive shift of the Pt 5d core level compared to Ge(100) and Pt(100) surfaces for the c(2 × 2)-Ge overlayer. There was no effect on these binding energies upon formation of the Pt2Ge layer compound at the surface, and this indicates similar Ge-Pt interactions in the two cases. Compared to other overlayers of Group-IV atoms on metal surfaces, the Ge overlayer on Pt(100) was extraordinarily stable.

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Section: Pt(100) Surfaces With Disordered Ge Layerssupporting

confidence: 92%

Section: Alissmentioning

confidence: 88%

Section: Stm and Leedmentioning

confidence: 99%