Evidence for an Order-Order Transition on the Ge(111) Surface near 1050 K from High-Resolution Helium Atom Scattering Experiments

Meli, C. A.; Greene, E. F.; Lange, Gerrit; Toennies, J. P.

doi:10.1103/physrevlett.74.2054

Cited by 39 publications

(40 citation statements)

References 13 publications

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“…Because of the low signal levels it was not possible to extract the pure elastic signal from time-of-flight measurements at each angle, as demonstrated earlier. 86 In this section only results for normal-H 2 /MgO have been presented; however, the same phases have been observed for adsorbates of para-H 2 and the heavier isotopomers. All of these adsorbates have been studied in more detail with inelatic He atom scattering as presented in the next section.…”

Section: A Growth and Structure Of H 2 õMgomentioning

confidence: 67%

Helium atom scattering studies of the structure and vibrations ofH2physisorbed on MgO(001) single crystals

et al. 2003

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The surface structure and vibrations of normal-H 2 , para-H 2 , HD, and normal-D 2 films physisorbed on in situ cleaved single crystal MgO͑001͒ surfaces, have been investigated at surface temperatures 7-12 K using high-resolution helium atom scattering. The He-diffraction patterns agree with the sequence of c(2ϫ2)c(4ϫ2)-c(6ϫ2) structures previously determined by neutron scattering. For the H 2 monolayer three different adsorbate frequencies, two Einstein modes around 10 meV and a dispersive mode between 2 and 7 meV, are found. HD and D 2 show the expected isotopomer shifts. A second probably ordered H 2 layer is formed upon further adsorption and exhibits one dispersionless mode at 5 meV.

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Section: A Growth and Structure Of H 2 õMgomentioning

confidence: 67%

Helium atom scattering studies of the structure and vibrations ofH2physisorbed on MgO(001) single crystals

et al. 2003

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“…Recent photoemission and photoabsorption spectroscopy experiments [5], ion scattering [6], electron-energy-loss spectroscopy [7], as well as ab initio molecular dynamics simulations [9] support a model which assumes that the top Ge bilayer is laterally diffusive, quasi-liquid-like, and metallic. In contrast, helium atom scattering (HAS) diffraction experiments [3,4] indicate that the HT surface is well ordered but exhibits a reduced surface corrugation consistent with an ordered metallic solid state. The later model finds support from earlier x-ray diffraction data [10] and from very recent metastable deexcitation spectroscopy experiments [11], which also find a surface metallization but still a preserved order at T .…”

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confidence: 98%

“…Thus, despite extensive experimental and theoretical studies [1,[3][4][5][6][7][8][9], the high temperature Ge(111) surface has so far eluded a clear description. Recent photoemission and photoabsorption spectroscopy experiments [5], ion scattering [6], electron-energy-loss spectroscopy [7], as well as ab initio molecular dynamics simulations [9] support a model which assumes that the top Ge bilayer is laterally diffusive, quasi-liquid-like, and metallic.…”

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confidence: 99%

Behavior of Single Adatoms on the Ge(111) Surface above the 1050 K Phase Transition

Glebov¹,

Toennies²,

Vollmer³

1999

Phys. Rev. Lett.

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The intensity of the quasielastic peak in He atom time-of-flight spectra reveals that, upon the 1050 K phase transition, the Ge adatom concentration on the Ge(111) surface rises from the 25% expected at T , T c to about 31% at T . T c . The wave vector dependence of the energetic broadening of the same peak indicates that above T c the adatoms jump to neighboring sites on a structurally well-defined substrate with a liquidlike diffusion coefficient of D ഠ 1.2 3 10 24 cm 2 ͞s. These new results reconcile previous conflicting descriptions of the Ge high-temperature phase and provide the first information on the dynamical behavior of single adatoms on a semiconductor surface close to its melting point. [S0031-9007(99)

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“…The optimum He reflectivity ͑ca. 30% at RT͒ and the sharpness of the diffraction peaks in the He-diffraction spectra as well as the reproduction of previously reported HAS spectra 8,24 were taken as criteria for the sample order and cleanliness. These features are known to be very sensitive to the surface coherence length and the presence of impurities on the surface.…”

Section: Methodsmentioning

confidence: 99%

Phonon dispersion curves of theGe(111)−c(2×8)surface determined by He atom scattering

et al. 2006

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The phonon dispersion curves of the Ge͑111͒-c͑2 ϫ 8͒ surface have been measured using high-resolution helium atom scattering. Experimental data points were obtained along two high-symmetry directions of the surface at room temperature and at 170 K. The main features are explained by a ͑2 ϫ 2͒ geometrical backfolding of the Rayleigh wave. The experimental phonon density of states obtained is qualitatively similar to the phonon density of states of the Si͑111͒-͑7 ϫ 7͒ surface.

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Evidence for an Order-Order Transition on the Ge(111) Surface near 1050 K from High-Resolution Helium Atom Scattering Experiments

Cited by 39 publications

References 13 publications

Helium atom scattering studies of the structure and vibrations ofH2physisorbed on MgO(001) single crystals

Helium atom scattering studies of the structure and vibrations ofH2physisorbed on MgO(001) single crystals

Behavior of Single Adatoms on the Ge(111) Surface above the 1050 K Phase Transition

Phonon dispersion curves of theGe(111)−c(2×8)surface determined by He atom scattering

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