EELS study of the clean and hydrogen-covered Mo(110) surface

Journal Article · Tue Apr 01 04:00:00 EST 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.55.10895· OSTI ID:561594

Kroeger, J; Lehwald, S; Ibach, H ^[1]

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1. Institut fuer Grenzflaechenforschung und Vakuumphysik des Forschungszentrums Juelich, D-52425 Juelich (Germany)

We have investigated both the substrate phonons and adsorbate vibrations of the clean and hydrogen-covered Mo(110) surface by high-resolution electron-energy-loss spectroscopy. With increasing hydrogen coverage the specular spectra together with elastic intensity measurements at {bar S} and {bar N} lead us to the conclusion that, in analogy to the W(110) surface, there exist three ordered phases at 110 K: three domains of a ``(2{times}1)`` at about 0.5 ML, a (2{times}2) at about 0.75 ML, and a (1{times}1) phase at full monolayer coverage. Starting from the elastic beam and extending up to the parallel hydrogen and deuterium vibration an enhanced background is observed for all phases in the specular spectra. The background increases monotonically with coverage. This background is probably partly due to an electron-hole damping mechanism and partly due to an enhanced mobility of the hydrogen adatoms. Additionally we present the dispersion of substrate phonons along the symmetry directions of the surface Brillouin zone. Our results confirm the helium atom scattering data and show that not only the Rayleigh wave but also the longitudinal mode exhibit a lowering of the frequency at a wave vector along {bar {Gamma}}{bar H} and at the {bar S} point. Moreover, we have discovered a shallow dip in the dispersion curve already for the (2{times}2) phase. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 561594
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 16 Vol. 55; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ADSORPTION
DISPERSION RELATIONS
HYDROGEN
LATTICE VIBRATIONS
MOLYBDENUM
PHONONS
RAYLEIGH WAVES
SURFACES