Percolation and localization dynamics in silicon nanocrystal films

ORAL

Abstract

We apply time-resolved THz spectroscopy [1] to probe the time progression of the ac-conductivity in optically excited Si nanocrystal (NC) films with varying Si vol {\%}, NC sizes and separations. A percolation transition is observed at 38 $\pm $ 1 vol {\%} Si. Above this threshold, we observe a transition form initial ($<$50 ps) long-range percolative inter-NC transport characterized by a non-zero DC conductivity to eventual localization of carriers at individual NCs. Below percolation threshold, early-time ($<$25 ps) inter-NC tunneling conduction is observed in films with sub-nm separations, followed by the final localization of the photoexcited carriers in the largest NCs. In the films with larger ($>$ 1 nm) inter-NC spacing, long-range transport is suppressed suggesting strong photoexcited carrier localization. Comparison of the observed dynamics to Monte Carlo simulations will be discussed. [1] D. G. Cooke et al, Phys. Rev. B \textbf{73}, 193311~(2006).

–

Authors

  • L.V. Titova

    Department of Physics, University of Alberta, Edmonton, Alberta T6G2G7 Canada, Department of Physics, University of Alberta, Edmonton, Alberta T6G 2G7, Canada, Department of Physics, University of Alberta, AB, Canada

  • T.L. Cocker

    Department of Physics, University of Alberta, Edmonton, Alberta T6G2G7 Canada, Department of Physics, University of Alberta, Edmonton, Alberta T6G 2G7, Canada, Department of Physics, University of Alberta, AB, Canada

  • X.Y. Wang

    Department of Physics, University of Alberta, Edmonton, Alberta T6G2G7 Canada

  • D.G. Cooke

    Department of Physics, University of Alberta, Edmonton, Alberta T6G2G7 Canada

  • A. Meldrum

    Department of Physics, University of Alberta, Edmonton, Alberta T6G2G7 Canada

  • F.A. Hegmann

    Department of Physics, University of Alberta, Edmonton, AB, T6G 2G7, Canada, Department of Physics, University of Alberta, Edmonton, Alberta T6G2G7 Canada, Department of Physics, University of Alberta, Edmonton, Alberta T6G 2G7, Canada, Department of Physics, University of Alberta, Edmonton, Alberta, Canada, Department of Physics, University of Alberta, AB, Canada