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Tunable terahertz photoconductivity of hydrogen functionalized graphene using optical pump-terahertz probe spectroscopy

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Abstract

We show that the terahertz photoconductivity of monolayer graphene following 800 nm femtosecond optical pump excitation can be tuned by different levels of hydrogenation (graphane) and provide a quantitative understanding of the unique spectral dependence of photoconductivity. The real part of terahertz photoconductivity (ΔσRe(ω)), which is negative in doped pristine graphene, becomes positive after hydrogenation. Frequency and electronic temperature Te dependent conductivity σ(ω, Te) is calculated using the Boltzmann transport equation taking into account the energy dependence of different scattering rates of the hot carriers. It is shown that the carrier scattering rate dominated by disorder-induced short-range scattering, though sufficient for pristine graphene, is not able to explain the observed complex Δσ(ω) for graphane. Our results are explained by considering the system to be heterogeneous after hydrogenation where conductivity is a weighted sum of conductivities of two parts: one dominated by Coulomb scattering coming from trapped charge impurities in the underlying substrate and the other dominated by short-range scattering coming from disorder, surface defects, dislocations and ripples in graphene flakes. A finite band gap opening due to hydrogenation is shown to be important in determining Δσ(ω).

Graphical abstract: Tunable terahertz photoconductivity of hydrogen functionalized graphene using optical pump-terahertz probe spectroscopy

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Publication details

The article was received on 23 May 2018, accepted on 19 Jun 2018 and first published on 02 Jul 2018


Article type: Paper
DOI: 10.1039/C8NR04154G
Citation: Nanoscale, 2018, Advance Article
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    Tunable terahertz photoconductivity of hydrogen functionalized graphene using optical pump-terahertz probe spectroscopy

    S. Kar, D. R. Mohapatra and A. K. Sood, Nanoscale, 2018, Advance Article , DOI: 10.1039/C8NR04154G

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