Probing Exciton Localization in Single-Walled Carbon Nanotubes Using High-Resolution Near-Field Microscopy

Georgi, Carsten; Green, Alexander A.; Hersam, Mark C.; Hartschuh, Achim

doi:10.1021/nn101443d

Cited by 35 publications

(33 citation statements)

References 32 publications

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“…We infer from this that the potential energy landscape indicated in Fig. 3b) also provides some of the sites at higher energies with sufficiently large barriers to exciton migration which cannot be overcome readily by average kinetic exciton energies of about 1 meV corresponding to the thermal energy at 17 K. Similar exciton localization has also been observed in single nanotube near-field PL studies by Georgi et al 47 Further support of diffusive exciton motion being responsible for ultrafast spectral diffusion can be obtained from the temperature dependent and spectrally resolved time-correlated single photon counting data shown in Fig. 4.…”

Section: A) B)supporting

confidence: 81%

Ultrafast Spectral Exciton Diffusion in Single-Wall Carbon Nanotubes Studied by Time-Resolved Hole Burning

et al. 2015

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We have studied ultrafast spectral diffusion (SD) within exciton bands of semiconducting single-wall carbon nanotubes (s-SWNTs) using one-and two-dimensional, near-infrared transient hole burning spectroscopy and time-resolved fluorescence spectroscopy at temperatures between 15 K and 293 K. We find that inhomogeneous spectral broadening of 60 meV for s-SWNTs embedded in gelatin exceeds the homogeneous linewidth of 3.3 meV by over an order of magnitude. The experiments show that ultrafast spectral diffusion of excitons in gel-immobilized s-SWNTs on the 250 fs time-scale can be attributed to axial intra-tube exciton diffusion. Comparison with kinetic Monte Carlo simulations suggests that the length-scale characteristic of the granularity of the axial potential energy landscape is about 24 nm.

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Section: A) B)supporting

confidence: 81%

Ultrafast Spectral Exciton Diffusion in Single-Wall Carbon Nanotubes Studied by Time-Resolved Hole Burning

et al. 2015

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“…Thus it appears that the purity of single photon antibunching is not severely affected by the presence of SD but depends rather on the degree of exciton localization along the tube axis, which is known to vary from tube to tube even at room temperature. 39 In addition to photon antibunching, we also observe pronounced side-peak bunching on the g 2 (τ) trace in Figure 5 at much longer time scales than the corresponding SD times of a few nanoseconds, which was never shown before for SWCNTs. This side-peak bunching is however typically observed in semiconductor QDs under resonant excitation of the p-shell and is interpreted to be caused by two-state submicrosecond blinking.…”

Section: Nano Letterssupporting

confidence: 58%

Quantum Light Signatures and Nanosecond Spectral Diffusion from Cavity-Embedded Carbon Nanotubes

2012

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Single-walled carbon nanotubes (SWCNTs) are considered for novel optoelectronic and quantum photonic devices, such as single photon sources, but methods must be developed to enhance the light extraction and spectral purity, while simultaneously preventing multiphoton emission as well as spectral diffusion and blinking in dielectric environments of a cavity. Here we demonstrate that utilization of nonpolar polystyrene as a cavity dielectric completely removes spectral diffusion and blinking in individual SWCNTs on the millisecond to multisecond time scale, despite the presence of surfactants. With these cavity-embedded SWCNT samples, providing a 50-fold enhanced exciton emission into the far field, we have been able to carry out photophysical studies for the first time with nanosecond timing resolution. We uncovered that fast spectral diffusion processes (1−3 ns) remain that make significant contributions to the spectral purity, thereby limiting the use of SWCNTs in quantum optical applications requiring indistinguishable photons. Measured quantum light signatures reveal pronounced photon antibunching (g 2 (0) = 0.15) accompanied by side-peak bunching signatures indicative of residual blinking on the submicrosecond time scale. The demonstrated enhanced single photon emission from cavity-embedded SWCNTs is promising for applications in quantum key distribution, while the demonstrated passivation effect of polystyrene with respect to the stability of the optical emission opens a novel pathway toward optoelectronic devices with enhanced performance.

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“…This could trap an exciton in a segment of the nanotube away from defects. 31 The nonradiative decay rate would decrease and thus the quantum efficiency would increase. Hence, we would expect a nanotube suspended in air to have a different diffusion constant from a nanotube on a surface or in a medium.…”

Section: N(t)mentioning

confidence: 99%

The Role of Length and Defects on Optical Quantum Efficiency and Exciton Decay Dynamics in Single-Walled Carbon Nanotubes

Harrah

Swan

2010

ACS Nano

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). The existence of a dark exciton level below the bright exciton band has been proposed as an explanation for low quantum efficiency.9 Spataru et al. showed that this splitting has minimal effect at room temperature, and the more important effect is the thermal momentum blocking of the radiative transition. 10The relatively low values of the quantum efficiency show that it is the nonradiative decay rate that dominates over the radiative decay rate. There are several nonradiative decay mechanisms proposed in the literature. At high fluences, excitonϪexciton Auger deexcitation has been suggested. 11,12 Furthermore, excitons in doped semiconducting nanotubes can decay via electronϪphonon interactions. 13 However, for undoped nanotubes in the linear regime, the main nonradiative decay mechanism is exciton diffusion to quenching sites, such as structural defects, adsorbate molecules, or the ends of the nanotube. 14Ϫ16 Stepwise fluorescence quenching in carbon nanotubes in response to changes to the nanotube's environment 16Ϫ18 can clearly also be utilized in sensor applications, such as biological sensors, ideally capable of detecting single molecules. 19The diffusion constant is the main parameter of the diffusion model, but it is not well-known. Experimentally extracted values of the diffusion constant range over 3 orders of magnitude, from 0.1 to 100 cm 2 /s. 12,16,18,20,21 Environment, chirality variation, length distributions, sample quality, and the presence of bundling introduce complexities in the behavior of the optical properties of nanotubes. Therefore, it is important to first examine the expected behavior of an individual nanotube with wellcontrolled static or dynamic quenching defects as the only interaction with the environment.In this paper, we assume that the observed diffusive behavior arises from random walks by excitons and perform Monte Carlo simulations of these random walks to model the fluorescence from nanotubes under uniform excitation (see Detailed Methods). From these simulations, we obtain the time-resolved, spatially resolved, and integrated quantum efficiency for nanotubes in the presence of perfectly quenching defects and of varying lengths. We show

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Probing Exciton Localization in Single-Walled Carbon Nanotubes Using High-Resolution Near-Field Microscopy

Cited by 35 publications

References 32 publications

Ultrafast Spectral Exciton Diffusion in Single-Wall Carbon Nanotubes Studied by Time-Resolved Hole Burning

Ultrafast Spectral Exciton Diffusion in Single-Wall Carbon Nanotubes Studied by Time-Resolved Hole Burning

Quantum Light Signatures and Nanosecond Spectral Diffusion from Cavity-Embedded Carbon Nanotubes

The Role of Length and Defects on Optical Quantum Efficiency and Exciton Decay Dynamics in Single-Walled Carbon Nanotubes

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