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

He, Wei, Yurkevich, Igor V., Zakar, Ammar and Kaplan, Andrey (2015). High-frequency conductivity of optically excited charge carriers in hydrogenated nanocrystalline silicon investigated by spectroscopic femtosecond pump-probe reflectivity measurements. Thin Solid Films, 592 , pp. 287-291.

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.

Publication DOI: https://doi.org/10.1016/j.tsf.2015.03.023
Divisions: Engineering & Applied Sciences > Mathematics
Engineering & Applied Sciences > Systems analytics research institute (SARI)
Additional Information: © 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)
Uncontrolled Keywords: high-frequency conductivity,nanomaterials,nanosilicon,ultrafast spectroscopy,Electronic, Optical and Magnetic Materials,Materials Chemistry,Metals and Alloys,Surfaces, Coatings and Films,Surfaces and Interfaces
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
Published Date: 2015-10-01
Authors: He, Wei
Yurkevich, Igor V. ( 0000-0003-1447-8913)
Zakar, Ammar
Kaplan, Andrey

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