Investigating surface dynamics with inelastic x-ray scattering

A brief overview of application of the grazing incidence inelastic x-ray scattering experimental method will be presented. Inelastic x-ray scattering in grazing incidence conditions provides a new tool for selectively studying both surface and bulk lattice dynamics in a single experiment. It is possible to study acoustic and optical surface phonon modes currently with a 3 meV resolution over a wide range of momentum space and make a direct comparison between surface and bulk dispersion. In particular the case of 2H-NbSe2 will be discussed. For this material a Kohn anomaly has been previously reported. Our data demonstrate that the softening of the Kohn anomaly at the 2H-NbSe2 surface is significantly greater than that reported for the bulk. This is an indication of a relaxation in the topmost layers of the crystal