PULSE Institute - Stanford University

Fourier-Transform Inelastic X-ray Scattering (FT-IXS) is a recently developed technique which utilizes the fine time resolution of ultrafast optical and x-ray lasers in conjunction with the high momentum sensitivity of diffusely scattered X rays. Via FT-IXS one can probe the dispersion curve of quantized acoustic excitations (phonons) with much reduced data collection time, with finer energy resolution, and with smaller samples than typical methods (e.g. inelastic neutron scattering (INS), inelastic x-ray scattering). Specifically, the FT-IXS technique is particularly suited to study nanostructured materials because of the more relaxed sample requirements (as enigineered samples are non-trivial to grow to sizes needed for INS) and because of the improved energy resolution (useful in comparing the subtle changes between nanostructured and host materials). We report recent studies from the Linac Coherent Light Source (LCLS) of GaAs embedded with nanoparticles of ErAs utilizing the FT-IXS technique. Specifically, we explored the changes in the phonon dispersion curve and phonon lifetimes induced by the presence of the nanoparticles. A better understanding of phonon scattering processes, hinted by their lifetimes, will enhance capabilities for tailoring thermal transport properties to various applications.