Diameter-dependent shielding effectiveness and terahertz conductivity of multiwalled carbon nanotubes

Polley, Debanjan; Neeraj, Kumar; Barman, Anjan; Mitra, Rajib Kumar

doi:10.1364/josab.33.002430

Cited by 14 publications

(11 citation statements)

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“…[215][216][217][218][219][220] Zhang et al [221] studied metallic and doped semiconductor SW CNTs films and demonstrated that the frequently observed localized response (or the so-called conductivity peak at finite frequency in the THz spectra) is due to a localized plasmon related to a finite length of the CNTs and their nonpercolation. The samples are usually prepared as self-standing films or films supported by a substrate.…”

Section: Thz Response Of Carbon Nanotubesmentioning

confidence: 99%

“…In a number of papers the THz conductivity of samples with nonaligned, partially aligned or completely aligned CNTs was interpreted within a Maxwell-Garnett effective medium model for composites with the intrinsic CNT conductivity described by a Drude term (to account for metallic nanotubes) and a harmonic oscillator term (to account for undoped semiconductor nanotubes). [215][216][217][218][219][220] Zhang et al [221] studied metallic and doped semiconductor SW CNTs films and demonstrated that the frequently observed localized response (or the so-called conductivity peak at finite frequency in the THz spectra) is due to a localized plasmon related to a finite length of the CNTs and their nonpercolation. In other words, the response can be described by an effective medium theory.…”

Section: Thz Response Of Carbon Nanotubesmentioning

confidence: 99%

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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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Section: Thz Response Of Carbon Nanotubesmentioning

confidence: 99%

Section: Thz Response Of Carbon Nanotubesmentioning

confidence: 99%

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

Kužel

Němec

2019

Advanced Optical Materials

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“…In closing this section, it might be well to mention that the extent of THz absorption by materials is governed by many parameters such as the type of filler, the thickness, F I G U R E 7 Shielding effectiveness of carbon-based thin films and graphene stacks; j -Sensale et al (2008), [35] k -Yan et al (2012), [32] l -Baek et al (2013), [46] m -Jung Taek et al(2012), [36] n -Seo et al (2008), [37] o -Das et al(2012), [33] p -Polley et al(2016), [44] q -Dong et al(2018) [47] and the nature of the matrix. It would be difficult to make any comparison between the materials, as several parameters are not mentioned in the available scientific literature.…”

Section: Carbon Thin Filmsmentioning

confidence: 99%

Carbon‐based terahertz absorbers: Materials, applications, and perspectives

et al. 2020

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Terahertz (THz) waves are nowadays used in a multitude of applications ranging from medicine, telecommunication, security surveillance, to fast sensing and imaging. Along with the most apparent aspects of the potential applications, there is also a flip side of the coin: the effects of unwanted electromagnetic pollution on various elements of the environment. Therefore, an effective shielding of THz radiation, preferably with an appreciable amount of absorption, is one of the milestones for the further development of terahertz technology. This review briefly outlines the main aspects of the area of research in terahertz absorbers, materials used, and their specific applications. Particular attention has been paid to the use of carbon-based materials as terahertz absorbers, needed to fill the gap between the well-known components across absorption coefficient 10-100 cm −1 for a refractive index 3-5. An example of such a class of materials is that of the organic or hybrid organic-inorganic polymers whose pyrolysis in an inert atmosphere gives black materials containing a residual free carbon phase. The carbon phase is a random network of covalent bonds in which carbon atoms are mainly in sp 2 hybridization state. The absorption of THz radiation is strongly dependent on the state of arrangement of C-sp 2 , the amount of carbon, and the graphitic carbon domain size. K E Y W O R D S absorbers, carbon, composites, submillimeter waves, terahertz 1 INTRODUCTION TO TERAHERTZ DOMAIN Terahertz (THz) waves are the electromagnetic (EM) waves covering the frequency gap that lies between microwaves and infrared radiations (Figure 1). The THz domain corresponds to frequencies of 0.3 THz-10 THz, which is equivalent to the wavelengths from 1 mm to 30 µm. [1] This EM This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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“…Traditional terahertz shielding materials are mainly composed of reflective materials because they reflect the incident terahertz wave by simply increasing conductivity . For example, it is reported that a terahertz‐shielding membrane prepared by a pyrolysis process for commercial polyimide has a very high reflectivity of more than 90% .…”

Section: Introductionmentioning

confidence: 99%

“…Second, reflective shielding materials usually have a large density. The reflective terahertz shielding material is mainly composed of polymer‐based membranes filled with conductive additives, such as metal particles, graphite, carbon nanotubes, carbon fiber, and other conductive additives . Their conductivity and terahertz shielding performance would only be remarkably enhanced when the conductive additives dispersed randomly in polymer matrix are integrated together to form a conductive network after the percolation threshold is exceeded.…”

Section: Introductionmentioning

confidence: 99%

Graphene‐Based Composites Combining Both Excellent Terahertz Shielding and Stealth Performance

Huang

Chen

et al. 2018

Advanced Optical Materials

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terahertz imaging, [9][10][11] terahertz detection, [12][13][14] and so on, terahertz related circuits and electronic components have been widely applied to current technologies. The fast-growing applications for terahertz waves have led to an urgent demand for terahertz shielding materials in order to effectively reduce the interference of terahertz wave signals, improve their transmission environment, and ensure that the delicate electronic instruments work as normal. Moreover, terahertz stealth materials also play a very important role in the fields of national security and information protection, which may help to avoid significant losses to individuals, enterprises, and even countries. Therefore, high-performance terahertz shielding/stealth materials have the potential for wide applications. [15] Traditional terahertz shielding materials are mainly composed of reflective materials because they reflect the incident terahertz wave by simply increasing conductivity. [16,17] For example, it is reported that a terahertz-shielding membrane prepared by a pyrolysis process for commercial polyimide has a very high reflectivity of more than 90%. [18] However, reflective shielding materials have two fatal flaws. First, reflective shielding materials cannot completely eliminate the interference of terahertz waves, because the reflected terahertz wave still adversely affects other sophisticated electronic elements inside the shielded devices. [19] Second, reflective shielding materials usually have a large density. The reflective Strong terahertz-response material which exhibits both excellent terahertz shielding and stealth performance is promising in practical applications of terahertz technology. Here, ultralight graphene foam (GF) and multiwalled carbon nanotubes/multiwalled graphene foam (MGF) have been first demonstrated to achieve both superior terahertz shielding and stealth performance due to the dominant absorption loss with negligible reflection. The terahertz shielding effectiveness values of GF and MGF, both 3 mm thick, reach up to 74 and 61 dB. Meanwhile, their average terahertz reflection loss values are achieved up to 23 and 30 dB, respectively, which are the best results in existing broadband terahertz shielding/stealth materials. Importantly, their qualified absorption bandwidths (reflection loss value larger than 10 dB) cover the entire measured frequency band of 0.1-1.6 THz. Furthermore, the quantitative relationships between the terahertz shielding effectiveness, reflection loss, and material parameters are accurately established, which should facilitate the material design for terahertz shielding and stealth. Comprehensively considering the important indicators of density, bandwidth, and intensity, the specific average terahertz shielding coefficient and the specific average terahertz absorption performance are achieved up to 1.1 × 10 5 and 3.6 × 10 4 dB cm 3 g −1 , respectively, which is over thousands of times larger than other kinds of materials reported previously. Shielding/Stealth MaterialsThe...

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Diameter-dependent shielding effectiveness and terahertz conductivity of multiwalled carbon nanotubes

Cited by 14 publications

References 39 publications

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

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

Carbon‐based terahertz absorbers: Materials, applications, and perspectives

Graphene‐Based Composites Combining Both Excellent Terahertz Shielding and Stealth Performance

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