High-frequency conductivity of optically excited charge carriers in hydrogenated nanocrystalline silicon investigated by spectroscopic femtosecond pump-probe reflectivity measurements

Wei He, Igor V. Yurkevich, Ammar Zakar, Andrey Kaplan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We report an investigation into the high-frequency conductivity of optically excited charge carriers far from equilibrium with the lattice. The investigated samples consist of hydrogenated nanocrystalline silicon films grown on a thin film of silicon oxide on top of a silicon substrate. For the investigation, we used an optical femtosecond pump-probe setup to measure the reflectance change of a probe beam. The pump beam ranged between 580 and 820nm, whereas the probe wavelength spanned 770 to 810nm. The pump fluence was fixed at 0.6mJ/cm2. We show that at a fixed delay time of 300fs, the conductivity of the excited electron-hole plasma is described well by a classical conductivity model of a hot charge carrier gas found at Maxwell-Boltzmann distribution, while Fermi-Dirac statics is not suitable. This is corroborated by values retrieved from pump-probe reflectance measurements of the conductivity and its dependence on the excitation wavelength and carrier temperature. The conductivity decreases monotonically as a function of the excitation wavelength, as expected for a nondegenerate charge carrier gas.

Original languageEnglish
Pages (from-to)287-291
Number of pages5
JournalThin Solid Films
Volume592
Early online date20 Mar 2015
DOIs
Publication statusPublished - 1 Oct 2015

Bibliographical note

© 2015, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

Funding: EPSRC (EP/K503873/1) and DSTL (DSTLX1000090880)

Keywords

  • high-frequency conductivity
  • nanomaterials
  • nanosilicon
  • ultrafast spectroscopy

Fingerprint Dive into the research topics of 'High-frequency conductivity of optically excited charge carriers in hydrogenated nanocrystalline silicon investigated by spectroscopic femtosecond pump-probe reflectivity measurements'. Together they form a unique fingerprint.

Cite this