Grazing-incidence inelastic X-ray scattering: lattice dynamics in thin films

Inelastic X-ray scattering is a powerful modern tool to study lattice dynamics of condensed matter. Recently an international team led by Dr. J. Serrano (Polytechnic University of Catalonia, Spain) has tried to extend the technique to several micron-thick systems by introducing grazing-incidence geometry. Their sample is indium nitride grown on a sapphire substrate with a gallium nitride buffer layer inbetween, but X-rays only probe the surface, and not the substrate underneath. The analysis was combined with ab initio calculations to determine the complete elastic stiffness tensor, the acoustic and low-energy optic phonon dispersion relations. This finding could be a help in developing new types of solar cells. For more information, see the paper, "InN Thin Film Lattice Dynamics by Grazing Incidence Inelastic X-Ray Scattering", J. Serrano et al., Phys. Rev. Lett. 106, 205501 (2011).