Universal ac conduction in large area atomic layers of CVD-grown MoS<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>

Ghosh, Sujoy; Najmaei, Sina; Kar, Swastik; Vajtai, Róbert; Lou, Jun; Pradhan, Nihar; Balicas, Luis; Ajayan, Pulickel M.; Talapatra, Saikat

doi:10.1103/physrevb.89.125422

Cited by 27 publications

(30 citation statements)

References 32 publications

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“…10. It is well known that the conductivity mechanism in any material could be understood from the temperature dependent behavior of n. To ascertain the electrical conduction mechanism in the materials, various models based on the variation of frequency exponent with temperature and frequency have been proposed such as quantum mechanical tunneling (QMT) model, [30][31][32] where conductivity is believed to be due to phonon-assisted tunneling between defect states; the overlapping large-polaron tunneling (OLPT) model, 31,33 in which tunneling of polarons is the dominant mechanism, here the large polaron wells at two sites overlap, thus reducing the polaron-hopping energy; and the correlated barrier hopping (CBH) model, 30,31 according to which the charge transport occurs between localized states due to hopping over the potential barriers. The temperature variation of exponent n correlates the ac conductivity mechanism as discussed below: 22 1.…”

Section: Ac Conductivitymentioning

confidence: 99%

Temperature dependent electrical transport characteristics of BaTiO3 modified lithium borate glasses

et al. 2015

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The glass samples with composition (70B2O3-29Li2O-1Dy2O3)-xBT; x = 0, 10 and 20 weight percent, have been prepared by conventional melt quench technique. The dielectric measurements as a function of temperature have been carried out on these samples in the frequency range 1 Hz-10 MHz. The dielectric relaxation characteristics of these samples have been studied by analyzing dielectric spectroscopy, dielectric loss, electric modulus formulation and electrical conductivity spectroscopy. It is found that the dielectric permittivity of the samples increases with an increase in the temperature and BT content. The frequency dependent ac conductivity has been analyzed using Jonscher’s universal power law whereas non exponential KWW function has been invoked to fit the experimental data of the imaginary part of the electric modulus. The values of the activation energy determined from the electric modulus and that from dc conductivity have been found to be quite close to each other suggesting that the same type of charge barriers are involved in the relaxation and the conduction mechanisms. The stretched exponent (β) and the power exponent (n) have been found to be temperature and composition dependent. The decrease in n with an increase in temperature further suggested that the ac conduction mechanism of the studied samples follows the correlated barrier hopping (CBH) model.

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Section: Ac Conductivitymentioning

confidence: 99%

Temperature dependent electrical transport characteristics of BaTiO3 modified lithium borate glasses

et al. 2015

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“…The variation of s with temperature is shown in the inset of Figure C. It is clear from the plot that s is almost independent of temperature within the studied temperature range (297–393 K) with a value of s ≈0.58 (±0.02). The temperature‐independence of s firmly indicates the incidence of phonon‐assisted simple quantum tunnelling between the localised defect states and σ′ ( ω )takes the functional forms given in Equation ():

σ^{'} (ω) = c e^{2} k_{B} T a {[N(E_{F})]}^{2} ω R_{ω}^{4}

…”

Section: Resultsmentioning

confidence: 99%

“…This power law equation [Eq. (3)]is widely used to describe the conductivity spectra below microwave frequency range . The conductivity isotherms are fitted to [Eq.…”

Section: Resultsmentioning

confidence: 99%

“…Scaling is a significant characteristic of the AC conductivity . Different sets of conductivity spectra can be made to collapse to one common curve by scaling, which indicates a common physical mechanism of AC conduction that is independent of time and temperature.…”

Section: Resultsmentioning

confidence: 99%

“…Primarily, DC conductivity gives macroscopic values because it is estimated on the transfer of charge species all over the sample controlled by the potential barrier of the ends, whereas frequency‐dependent conductivity traces the back and forth motion of charges. Dielectric relaxation spectroscopy is one of the familiar techniques for investigating molecular dynamics in order–disorder systems . The charge transport properties of RGO‐based composites are directly related to the ratio of order–disorder domains present in RGO .…”

Section: Introductionmentioning

confidence: 99%

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AC Conduction and Time–Temperature Superposition Scaling in a Reduced Graphene Oxide–Zinc Sulfide Nanocomposite

et al. 2016

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We report, herein, the results of an in depth study and concomitant analysis of the AC conduction [σ'(ω): f=20 Hz to 2 MHz] mechanism in a reduced graphene oxide-zinc sulfide (RGO-ZnS) composite. The magnitude of the real part of the complex impedance decreases with increase in both frequency and temperature, whereas the imaginary part shows an asymptotic maximum that shifts to higher frequencies with increasing temperature. On the other hand, the conductivity isotherm reveals a frequency-independent conductivity at lower frequencies subsequent to a dispersive conductivity at higher frequencies, which follows a power law [σ'(ω)∝ω(s) ] within a temperature range of 297 to 393 K. Temperature-independent frequency exponent 's' indicates the occurrence of phonon-assisted simple quantum tunnelling of electrons between the defects present in RGO. Finally, this sample follows the "time-temperature superposition principle", as confirmed from the universal scaling of conductivity isotherms. These outcomes not only pave the way for increasing our elemental understanding of the transport mechanism in the RGO system, but will also motivate the investigation of the transport mechanism in other order-disorder systems.

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Reduced Graphene Oxide ‐ Zinc Phthalocyanine Composites as Fascinating Material for Optoelectronic and Photocatalytic Applications

et al. 2017

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Reduced graphene oxide‐ zinc tetra tert‐butyl phthalocyanine (RGO‐ZnTTBPc) hybrid material has been synthesized through the reduction of graphene oxide (GO) in presence of ZnTTBPc. As‐prepared RGO‐ZnTTBPc thin film photodetector exhibited stable and reproducible photocurrent responses with a responsivity of 2 A/W under simulated solar light.A detailed study on electrical transport mechanism reveals the occurrence of phonon assisted quantum tunneling of charge carriers among the defect states present in RGO ‐ ZnTTBPc system. The relaxation dynamics of charge carriers in the composite is modulated by a temperature independent universal function. Furthermore, the resulting hybrid material showed an enhanced photocatalytic activity with 3.5 times higher reduction rate constant over controlled ZnTTBPc towards the reduction of 4‐nitrophenol under solar light irradiation. Superior photoresponse property and photocatalytic reduction was attributed to the synergistic effect between favorable matching of the lowest unoccupied molecular orbital (LUMO) level of ZnTTBPc to the work function of conductive RGO. The present work is especially important in the field of RGO‐based next‐generation photocatalysts and light energy harvesting applications.

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Universal ac conduction in large area atomic layers of CVD-grown MoS2

Cited by 27 publications

References 32 publications

Temperature dependent electrical transport characteristics of BaTiO3 modified lithium borate glasses

Temperature dependent electrical transport characteristics of BaTiO3 modified lithium borate glasses

AC Conduction and Time–Temperature Superposition Scaling in a Reduced Graphene Oxide–Zinc Sulfide Nanocomposite

Reduced Graphene Oxide ‐ Zinc Phthalocyanine Composites as Fascinating Material for Optoelectronic and Photocatalytic Applications

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