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Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P298
Phonon modes at the 2H–NbSe2 surface observed by surface sensitive inelastic
X-ray scattering
Bridget Murphy 1 , Herwig Requardt 2 , Jochim Stettner 1 , Jorge Serrano 2 ,
Michael Krisch 2 , Martin Müller 1 , Werner Press 1,3
1 IEAP, CAU Kiel, Olshausenstraße 40, D-24098 Kiel, Germany – 2 ESRF, BP220, 38043
Grenoble Cedex, France – 3 ILL, BP156, 38042 Grenoble Cedex 9, France
We have determined the dispersion of acoustic and optical surface phonon modes at
the 2H–NbSe2 surface by inelastic x–ray scattering under grazing incidence conditions.
Already, at room temperature, an anomaly is observed close to the charge density wave
Q–vector position located at about one-third along the Γ-M direction of the Brillouin
zone [1]. Our results indicate that the anomaly for the surface mode occurs at a lower
energy than that measured in bulk sensitive geometry in the same experiment, showing
evidence of a modified behaviour in the uppermost layers. Temperature–dependent
softening is observed in both surface and bulk. We demonstrate that inelastic x–ray
scattering in grazing incidence conditions provides a unique tool to selectively study
either surface or bulk lattice dynamics in a single experiment.
[1] B. M. Murphy, H. Requardt, J. Stettner, J. Serrano, M. Krisch, M. Müller, W.
Press, Phys. Rev. Lett. 95 (2005) 256104.