1 Department of Photonics Engineering, Technical University of Denmark2 Teraherts Technologies and Biophotonics, Department of Photonics Engineering, Technical University of Denmark3 McGill University4 University of Alberta5 Center for Nanostructured Graphene, Center, Technical University of Denmark6 McGill University7 University of Alberta
The terahertz conductivity of silicon nanoparticles embedded in glass with varying density is studied with ultra-broadband terahertz spectroscopy on picosecond time scales following fs optical excitation. The transition from relatively isolated charge carriers to densities which allow inter-particle transport is clearly observed. For the times immediately following carrier injection, we observe Drude-like long range transport that is rapidly replaced with a localized response on picosecond time scales. The localized response can be very well described by a phenomenological Drude-Smith model, verifying the applicability of this simple model to the conductivity of nanoparticle ensembles over the entire THz spectral window.