Mechanism of the Far-Infrared Absorption of Carbon-Nanotube Films

Kampfrath, Tobias; Volkmann, Konrad von; Aguirre, Carla; Desjardins, P.; Martel, Richard; Krenz, M.; Frischkorn, Christian; Wolf, Martin; Perfetti, L.

doi:10.1103/physrevlett.101.267403

Cited by 82 publications

(88 citation statements)

References 32 publications

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“…Phonons and plasmons have thus been proposed as alternative mechanisms. Kampfrath et al (2008) were able to show that the weak temperature dependence is consistent with the picture of interband transitions in small gap SWNTs if there is an NT-to-NT variation of the chemical potential.…”

Section: Graphitic Nanostructuressupporting

confidence: 58%

“…A large anisotropy between the direction parallel and perpendicular to the NT axis was observed in aligned NT films. A more comprehensive study of the equilibrium far-IR properties of SWNTs was reported by Kampfrath et al (2008). The complex dielectric response or conductivity over a broad spectral range (1-40 THz) was measured for films of high pressure CO grown NTs (Fig.…”

Section: Graphitic Nanostructuresmentioning

confidence: 99%

“…The THz conductivity of photoexcited carbon NTs has been investigated independently by several groups (Perfetti et al, 2006;Beard et al, 2008;Kampfrath et al, 2008;Xu et al, 2009). Distinct response was observed and based on these results controversial conclusions were drawn regarding the primary product of photoexcitation in SWNTs.…”

Section: Graphitic Nanostructuresmentioning

confidence: 99%

“…Distinct response was observed and based on these results controversial conclusions were drawn regarding the primary product of photoexcitation in SWNTs. In the study of high pressure CO grown NT films in a broad THz frequency range, Perfetti et al (2006), Kampfrath et al (2008), and coworkers observed the absence of the characteristic free-carrier response-a negative real part of the complex dielectric function-in the pump-induced optical conductivity. The absence of free-electron response was attributed by them to the strongly bound excitons in SWNTs with large energy gaps as the primary photo-excitation product (Perfetti et al, 2006).…”

Section: Graphitic Nanostructuresmentioning

confidence: 99%

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Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

et al. 2011

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Time-resolved, pulsed terahertz spectroscopy has developed into a powerful tool to study charge carrier dynamics in semiconductors and semiconductor structures over the past decades. Covering the energy range from a few to about 100 meV, terahertz radiation is sensitive to the response of charge quasiparticles, e.g., free carriers, polarons, and excitons. The distinct spectral signatures of these different quasiparticles in the THz range allow their discrimination and characterization using pulsed THz radiation. This frequency region is also well suited for the study of phonon resonances and intraband transitions in low-dimensional systems. Moreover, using a pump-probe scheme, it is possible to monitor the nonequilibrium time evolution of carriers and low-energy excitations with sub-ps time resolution. Being an all-optical technique, terahertz time-domain spectroscopy is contact-free and noninvasive and hence suited to probe the conductivity of, particularly, nanostructured materials that are difficult or impossible to access with other methods. The latest developments in the application of terahertz time-domain spectroscopy to bulk and nanostructured semiconductors are reviewed.

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Section: Graphitic Nanostructuressupporting

confidence: 58%

Section: Graphitic Nanostructuresmentioning

confidence: 99%

Section: Graphitic Nanostructuresmentioning

confidence: 99%

Section: Graphitic Nanostructuresmentioning

confidence: 99%

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Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

et al. 2011

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“…Evidence for such transitions for quasimetallic CNTs was presented in experiments on the absorption of CNT films in the far-infrared part of the spectrum. 19 In our case the asymmetry of the devices will result in different gate efficiencies for the suspended and the nonsuspended parts of a CNT the shift of the bands with respect to the Fermi level will be different. Therefore the devices we study have p-n junctions on the current path from one electrode to another at a certain range of gate voltages.…”

mentioning

confidence: 88%

Photothermoelectric response in asymmetric carbon nanotube devices exposed to sub-terahertz radiation

Fedorov

Кардакова

Gayduchenko

et al. 2013

Applied Physics Letters

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We report on the voltage response of carbon nanotube devices to sub-terahertz (THz) radiation. The devices contain carbon nanotubes (CNTs), which are over their length partially suspended and partially Van der Waals bonded to a SiO 2 substrate, causing a difference in thermal contact. We observe a DC voltage upon exposure to 140 GHz radiation. Based on the observed gate voltage and power dependence, at different temperatures, we argue that the observed signal is both thermal and photovoltaic. The room temperature responsivity in the microwave to THz range exceeds that of CNT based devices reported before. The unique band structure of carbon nanotubes (CNT) makes them good candidates for optoelectronic applications in a wide frequency range. [1][2][3] Due to the quantization of the electron wave vector around the circumference a CNT with n -m 6 ¼ 3i, where i is an integer is a semiconductor with an energy gap e g $ 1/r (with r the radius of the CNT). 4 The optical properties of semiconducting nanotubes, in the visible and near infrared range, have been intensely studied during the last ten years. 1,5,6 It has been shown that they can be used as basic elements for different optoelectronic functions, such as photodetectors 6 or light emitting diodes. 7 Nanotubes, with n -m ¼ 3i, with n 6 ¼ m, are called quasi-metallic, due to their small band gap, which ranges from about 1 to about 30 meV for nanotubes with a diameter of 1-2 nm. 8,9 Socalled armchair CNTs, with n ¼ m, are truly metallic. Quasi-metallic CNTs are potentially very good candidates for optoelectronics in the THz range because their bandgaps fall into the corresponding energy range.Previous research on THz detectors based on CNTs has brought interesting new results. 3,10 Diode type detection and bolometric detection were reported in Refs. 3 and 10. Photonassisted tunneling in the Coulomb blockade regime was reported in Ref. 11. The response of antenna-coupled fully suspended single carbon nanotubes to sub-THz radiation was reported in Ref.12. A power-dependent DC voltage was reported in this work and interpreted as a combined effect of the increased temperature of the electron liquid with respect to the electrodes and requiring an asymmetry in the contact resistances.Here we report on CNT devices, which will have a temperature gradient due to a difference in heat transfer along the CNTs while exposed to radiation. The different heat transfer conditions occur because of a difference in coupling to the substrate along the length. The devices show a DC voltage signal in response to radiation in the sub-THz range in the temperature range from 4.2 to 300 K. We argue that the room temperature response is thermal in origin, similarly to the photoresponse of CNT films reported before, e.g., in Ref. 13. The data obtained at low temperatures indicate contributions of both thermal effects and of photovoltaic effects. While it is not clear if the observed effect can be used to develop efficient THz detectors we note that the responsivity of our devices exceeds that ...

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The Transient Localization Scenario for Charge Transport in Crystalline Organic Materials

Fratini

Mayou

Ciuchi

2016

Adv Funct Materials

339

452

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Charge transport in crystalline organic semiconductors is intrinsically limited by the presence of large thermal molecular motions, which are a direct consequence of the weak van der Waals inter-molecular interactions. These lead to an original regime of transport called transient localization, sharing features of both localized and itinerant electron systems. After a brief review of experimental observations that pose a challenge to the theory, we concentrate on a commonly studied model which describes the interaction of the charge carriers with inter-molecular vibrations. We present different theoretical approaches that have been applied to the problem in the past, and then turn to more modern approaches that are able to capture the key microscopic phenomenon at the origin of the puzzling experimental observations, i.e. the quantum localization of the electronic wavefuntion at timescales shorter than the typical molecular motions. We describe in particular a relaxation time approximation which clarifies how the transient localization due to dynamical molecular motions relates to the Anderson localization realized for static disorder, and allows us to devise strategies to improve the mobility of actual compounds. The relevance of the transient localization scenario to other classes of systems is briefly discussed.

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Mechanism of the Far-Infrared Absorption of Carbon-Nanotube Films

Cited by 82 publications

References 32 publications

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

Photothermoelectric response in asymmetric carbon nanotube devices exposed to sub-terahertz radiation

The Transient Localization Scenario for Charge Transport in Crystalline Organic Materials

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