THz photoconductivity in light-emitting surface-oxidized Si nanocrystals: the role of large particles

Zajac, V.; Němec, H.; Kadlec, C.; Kůsová, Kateřina; Pelant, I.; Kužel, Petr

doi:10.1088/1367-2630/16/9/093013

Cited by 23 publications

(35 citation statements)

References 33 publications

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“…23,29,[34][35][36]39,71,73,76 Alternatively, the Drude-Smith model has also been used as an EMT in its own right and fit directly to the measured THz conductivity. [9][10][11][12][13][14][15][16][17][18][19]21,22,[25][26][27]30,31,33,38,[41][42][43][44][45]48 Each approach begins with a different physical process and leads to its own difficulties when one interprets the subsequent fits to the data.…”

Section: −48mentioning

confidence: 99%

“…26 ) Nevertheless, depolarization fields do play an important role in determining the macroscopic THz conductivities of some non-percolated systems. [64][65][66][67][70][71][72][73][74] In these cases, the strong dependence of depolarization-based conductivity suppression on car-rier density can be used to distinguish it from weak carrier confinement, though it remains unclear how best to combine the two effects. In the following we focus specifically on the microscopic conductivity of weakly confined systems and its relationship to the Drude-Smith model.…”

Section: −48mentioning

confidence: 99%

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Microscopic origin of the Drude-Smith model

et al. 2017

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The Drude-Smith model has been used extensively in fitting the THz conductivities of nanomaterials with carrier confinement on the mesoscopic scale. Here, we show that the conventional 'backscattering' explanation for the suppression of low-frequency conductivities in the Drude-Smith model is not consistent with a confined Drude gas of classical non-interacting electrons and we derive a modified Drude-Smith conductivity formula based on a diffusive restoring current. We perform Monte Carlo simulations of a model system and show that the modified Drude-Smith model reproduces the extracted conductivities without free parameters. This alternate route to the DrudeSmith model provides the popular formula with a more solid physical foundation and well-defined fit parameters.

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Section: −48mentioning

confidence: 99%

Section: −48mentioning

confidence: 99%

Microscopic origin of the Drude-Smith model

et al. 2017

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“…[63] This expression can be also understood as a Maxwell-Garnett formula with, in addition, ad hoc percolated volume V. [80] Resonant behavior of the second term in (9) then represents the plasmon in the THz spectrum; its frequency will exhibit a specific dependence on the carrier concentration N encoded in the frequency and carrier density dependence of Δσ loc . [63] This expression can be also understood as a Maxwell-Garnett formula with, in addition, ad hoc percolated volume V. [80] Resonant behavior of the second term in (9) then represents the plasmon in the THz spectrum; its frequency will exhibit a specific dependence on the carrier concentration N encoded in the frequency and carrier density dependence of Δσ loc .…”

Section: Effective Medium Approach and Localized Plasmon Resonancementioning

confidence: 99%

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Kužel

Němec

2019

Advanced Optical Materials

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Transport of charges is a fundamental process in many high-tech applications including photovoltaic or optoelectronic devices, but also in more ordinary components such as unsophisticated wires and other circuitry. The development of nanotechnologies resulted in the fabrication of highly complex materials consisting of a large variety of nanosized elements, which inevitably involve a multitude of charge transport processes occurring on various time-and length-scales. Figure 1 summarizes the most common nanoelements with high application potential.For example, the electrodes employed in Grätzel solar cells [1] are composed of percolated networks of a huge number of metal oxide nanoparticles (top-left panel in Figure 1). Colloidal nanocrystals form the basis for thin film electronics and flexible electronic devices. [2] The synthetic approaches control their composition, size and electronic structure (energy levels, density of states within the bands and in the bandgap) and the charge-carrier transport. [2,3] Nanowires and nanotubes made of conventional semiconductors are quasi 1D systems combining Terahertz spectroscopy has been used for almost two decades for investigations of nanomaterials, including nanocrystals, nanoparticles, nanowires, nanotubes or 2D crystals. Its great importance stems from the fact that it is a noncontact method and, owing to its high frequency and broadband character, it is capable of characterizing charge transport properties within individual nano-objects but also among them. In addition, probing of photoinitiated ultrafast charge dynamics is possible thanks to the sub-picosecond time resolution. Despite this unprecedented potential, the interpretation of the measured terahertz conductivity spectra in many materials is still intensively debated. Herein is presented a review of the experiments performed on nanostructures of conventional semiconductors and on carbon nanomaterials (graphene and carbon nanotubes) during the past decade. The state of the art of the theoretical formalism is provided and discussed, including the intrinsic response, as well as the role of inherent heterogeneity and of the experimental conditions.

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“…as an experimental spectrum in this paper and reflects both 199 the evolution of the mobility spectra and the carrier density T norm introduced in [9,14]: these two quantities differ just by 202 a multiplication factor,…”

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confidence: 92%

Picosecond charge transport in rutile at high carrier densities studied by transient terahertz spectroscopy

2016

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We study terahertz photoconductivity of a rutile single crystal between 10 and 300 K under strong photoexcitation by femtosecond pulses at 266 nm. A marked dependence of the carrier mobility on the carrier density is observed leading to highly complex transport phenomena on a picosecond time scale. We develop a general model of carrier photoconductive response in the case of time dependent inhomogeneous distribution of carrier density and mobility. This allows us to assess an important role of both electrons and holes in the response of photoexcited rutile. At low temperatures, the carrier mobility is initially reduced due to the electron-hole scattering and increases by one order of magnitude upon ambipolar diffusion of the carriers into deeper regions of the sample. At room temperature, contributions of transient hot optical phonons and/or of midinfrared polaron excitations with charge-density-dependent dielectric strength emerge in the photoconductivity spectra.

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THz photoconductivity in light-emitting surface-oxidized Si nanocrystals: the role of large particles

Cited by 23 publications

References 33 publications

Microscopic origin of the Drude-Smith model

Microscopic origin of the Drude-Smith model

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Picosecond charge transport in rutile at high carrier densities studied by transient terahertz spectroscopy

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