Carrier dynamics and conductivity of SnO2 nanowires investigated by time-resolved terahertz spectroscopy

Τσόκκου, Δήμητρα; Othonos, Andreas; Zervos, Matthew

doi:10.1063/1.3698097

Cited by 44 publications

(65 citation statements)

References 26 publications

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“…Therefore, we consider μ h = 72/5 = 14.4 cm 2 /(V·s). This value falls between those measured previously3839.…”

Section: Resultssupporting

confidence: 86%

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Promotion of acceptor formation in SnO2 nanowires by e-beam bombardment and impacts to sensor application

Kim

et al. 2015

Sci Rep

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We have realized a p-type-like conduction in initially n-type SnO2 nanowires grown using a vapor-liquid-solid method. The transition was achieved by irradiating n-type SnO2 nanowires with a high-energy electron beam, without intentional chemical doping. The nanowires were irradiated at doses of 50 and 150 kGy, and were then used to fabricate NO2 gas sensors, which exhibited n-type and p-type conductivities, respectively. The tuneability of the conduction behavior is assumed to be governed by the formation of tin vacancies (under high-energy electron beam irradiation), because it is the only possible acceptor, excluding all possible defects via density functional theory (DFT) calculations. The effect of external electric fields on the defect stability was studied using DFT calculations. The measured NO2 sensing dynamics, including response and recovery times, were well represented by the electron-hole compensation mechanism from standard electron-hole gas equilibrium statistics. This study elucidates the charge-transport characteristics of bipolar semiconductors that underlie surface chemical reactions. The principles derived will guide the development of future SnO2-based electronic and electrochemical devices.

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“…Therefore, we consider μ h = 72/5 = 14.4 cm 2 /(V·s). This value falls between those measured previously3839.…”

Section: Resultssupporting

confidence: 86%

“…The hole mobility in SnO 2 (which is lower than the electron mobility) is reported to be ~6 cm 2 /(V·s) in Mn-doped SnO 2 38 and ~39 cm 2 /(V·s) in In-Ga codoped SnO 2 39. In this study, we assume μ e = 5 × μ h .…”

Section: Resultsmentioning

confidence: 95%

Promotion of acceptor formation in SnO2 nanowires by e-beam bombardment and impacts to sensor application

Kim

et al. 2015

Sci Rep

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“…[110] In even smaller (nanometersized) nanocrystals, the first excitonic transition appears far above the THz range. [114] Regardless of the nanoparticle shape, size and spatial distribution and orientation, many works still employ the Drude-Smith model as a base for fitting the THz conductivity spectra of a variety of nanostructures, including silicon nanowires, [115] nanocrystals [116][117][118] and polycrystalline films, [119] SnO 2 nanowires, [120][121][122] nanowhiskers [123] and mesoporous films, [124] CdSe nanobelts, [125] CdS x Se 1−x nanobelts [126,127] and nanowires, [128] ZnSe nanocrystals, [129] Au nanostructures, [130] granular kesterite films, [131] organic perovskite CsPbBr 3 nanocrystals, [132] VO 2 nanogranular films, [133,134] or graphene nanoribbons. [111,112] The excitonic polarizability can be calculated on a microscopic level, e.g., using a multiband effectivemass model.…”

Section: Wwwadvopticalmatdementioning

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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“…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. In the former case, depolarization fields are included explicitly and treated as independent from weak confinement.…”

Section: −48mentioning

confidence: 99%

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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Carrier dynamics and conductivity of SnO2 nanowires investigated by time-resolved terahertz spectroscopy

Cited by 44 publications

References 26 publications

Promotion of acceptor formation in SnO2 nanowires by e-beam bombardment and impacts to sensor application

Promotion of acceptor formation in SnO2 nanowires by e-beam bombardment and impacts to sensor application

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

Microscopic origin of the Drude-Smith model

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