Investigation of surface phonons by inelastic helium atom scattering of the Bi(111) surface

Michael Mayrhofer-Reinhartshuber, Anton Tamtögl, Patrick Kraus, Wolfgang Ernst, Davide Campi, Giorgio Benedek

Research output: Chapter in Book/Report/Conference proceedingConference paperpeer-review

Abstract

The remarkable differences between its bulk and surface properties make the semimetal
Bismuth (Bi) an interesting candidate for the investigation of surface phonons, because in
contrast to the bulk not much is known about their behaviour. [1] With the strictly surface
sensitive technique of inelastic helium atom scattering (HAS) the observation of these
quanta of lattice vibrations on the surface is possible.
Since first results of our measurements were published in [2], additional data was gained
with enhanced data analysis and new measurements:
Time-of-flight (TOF) spectra using HAS from the (111) surface of a Bi single crystal at room
temperature, which were used for determining the surface phonon dispersion curve, were
reviewed with improved algorithms reducing the noise level on the phonon-creation side of
the spectra. Additional peaks were revealed, which were analyzed for their possible origin
in excited surface phonons in acoustical or optical modes.
Further the obtained data was compared with ab-initio calculations of antimony (Sb), which
has a similar crystal structure as bismuth. Weaker spin-orbit coupling of Sb compared to Bi
makes it more accesible for theory while the similarities in geometry makes a comparism
reasonable. It reveals that a phonon mode measured with a nearly flat dispersion, which is
usually typical for the optical branch, is an additional acoustical mode, while the estimated
optical mode should occur at a higher energy.
Recent measurements performed with sample temperatures down to 115 K give more
clearly resolved spectra because of the repression of multiphonon influences. Experiments
using a helium beam with a larger energy up to 20 meV made it possible to reach the
estimated region of the optical surface phonon branch.
Original languageEnglish
Title of host publicationSurface Dynamics
Pages92-92
Publication statusPublished - 2011
Event28th European Conference on Surface Science - Wroclaw, Poland
Duration: 28 Aug 20112 Sept 2011

Conference

Conference28th European Conference on Surface Science
Country/TerritoryPoland
CityWroclaw
Period28/08/112/09/11

Fields of Expertise

  • Advanced Materials Science

Treatment code (Nähere Zuordnung)

  • Basic - Fundamental (Grundlagenforschung)
  • Experimental

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