Crossover from Mott to Efros-Shklovskii variable-range-hopping conductivity in conducting polyaniline

Ghosh, Manas; Barman, Abhisikta; De, Sourya Joyee; Chatterjee, S.

doi:10.1016/s0379-6779(98)00105-2

Cited by 35 publications

(21 citation statements)

References 22 publications

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“…Conducting polymers are predominantly polycrystalline or amorphous in character and have a substantial amount of disorder. The disorder arises during the synthesis processing, and through the presence of partial crystallinity and impurities, lack of long‐range order, etc 8. Furthermore, the number of defects also depends appreciably on the conditions under which the film is prepared.…”

Section: Resultsmentioning

confidence: 99%

Space‐charge limited conduction in polyaniline films

Nazeer

Jacob

Thamilselvan

et al. 2004

Polymer International

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Polyaniline emeraldine base (PANI‐EB) powder was synthesized by oxidative polymerization of aniline. The PANI‐EB films were prepared by the solution‐casting technique. The temperature‐dependent dc conductivity measured in the range 173–303 K suggests that the PANI‐EB is a quasi‐one‐dimensional disordered conductor. The current‐voltage characteristics of the PANI‐EB films measured in the range 333–383 K showed the SCLC mechanism. The SCLC parameters such as free carrier density (p0), trap density (pt), the ratio between free carrier density to the total carrier density (θ), mobility (µ) and the effective hole mobility (µeff) were calculated. The activation energy (Ea = 0.32 eV) and the Fermi level (EF = 0.42 eV) were estimated. As well as these, the trap parameters such as the trap filled limit voltage (VTFL), the shallow trap density (Nt), the depth of the dominant trap level (Et − Ev), the density of states within the hole mobility edge (Nv) and the characteristic energy (Ec) were also calculated and presented. The exponential type of traps distribution with large number of traps was found to be due to the disorder and moisture in the polymer films. Copyright © 2004 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 99%

Space‐charge limited conduction in polyaniline films

Nazeer

Jacob

Thamilselvan

et al. 2004

Polymer International

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“…4 However, an unexpected positive temperature coefficient 5-7 is found for the transversal resistance whichalthough within a more modest range of variationdecreases slightly. If we assume a typical value of 20 Å for the thickness of each bilayer, 1,8 the individual longitudinal and transversal components of the resistivity tensor of these thin polymeric films can be estimated.…”

Section: A Longitudinal Resistivitymentioning

confidence: 90%

“…Two different conduction regimes are revealed in the above curves: a high-temperature (50 KϽT Ͻ300 K) region of moderate change of the resistivity with decreasing temperatures 3 and a low-temperature regime (T Ͻ50 K), characterized by a sudden increase of the resistivity values. 4 An analysis of the corresponding activation energies 9 revealed that this modification in the thermal gradient of the resistivity can be associated to a change in the dimensionality of the dominating microscopic charge transfer process. 10 The variable range hopping model 11,12 assumes ϭ 0 exp͓(ϪT 0 /T) 1/(dϩ1) ͔ and is commonly adopted to relate the temperature dependence of the conductivity to the dimensionality d of the charge transport in organic samples.…”

Section: A Longitudinal Resistivitymentioning

confidence: 99%

Low-temperature electrical anisotropy of self-assembled organic films

Melo

2002

Phys. Rev. B

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We have examined the low-temperature characteristics of the charge transport in self-assembled organic films with thickness varying from 5 to 60 deposited bilayers of polypyrrole and polythiophene acetic acid. When the temperature is progressively decreased, independent measurements of the longitudinal and transversal components of the resistivity tensor of these thin films reveal that while the conductivity along the surface directions has the expected semiconducting profile, the charge transport in the transversal direction exhibits a positive temperature coefficient ͑PTC͒. For the samples with a small number of deposited bilayers we observe that at very low temperatures the PTC characteristics disappear and a tunnelinglike current begins to dominate the transversal charge transport.

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“…Polyaniline is one of the potential conducting polymers due to low‐cost synthesis, fast processability, flexible properties, and environmental stability. However, its electron transport mechanism is still under debate []. Additionally, small pieces of reduced graphene oxides (rGOs), which are reduced from graphene oxides (GOs), are picked up as a 2D material for DEP experiments.…”

Section: Introductionmentioning

confidence: 99%

Dielectrophoretic placement of quasi‐zero‐, one‐, and two‐dimensional nanomaterials into nanogap for electrical characterizations

et al. 2012

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DEP is one of promising techniques for positioning nanomaterials into the desirable location for nanoelectronic applications. In contrast, the lithography technique is commonly used to make ultra-thin conducting wires and narrow gaps but, due to the limit of patterning resolution, it is not feasible to make electrical contacts on ultra-small nanomaterials for a bottom-up device fabrication. Thus, integrating the lithography and dielectrophoresis, a real bottom-up fabrication can be achieved. In this work, the device with the nanogap in between two nanofinger-electrodes is made using electron-beam lithography from top down and the ultra-small nanomaterials, such as colloidal PbSe quantum dots, polyaniline nanofibers, and reduced-graphene-oxide flakes, are placed in the nanogap by DEP from bottom up. The threshold electric field for the DEP placement of PbSe nanocrystals was roughly estimated to be about 8.3 × 10(4) V/cm under our experimental configuration. After the DEP process, several procedures for reducing contact resistances are attempted and measurements of intrinsic electron transport in versatile nanomaterials are performed. It is experimentally confirmed that electron transport in both PbSe nanocrystal arrays and polyaniline nanofibers agrees well with Prof. Ping Sheng's model of granular metallic conduction. In addition, electron transport in reduced-graphene-oxide flakes follows Mott's 2D variable-range-hopping model. This study illustrates an integration of the electron-beam lithography and the DEP techniques for a precise manipulation of nanomaterials into electronic circuits for characterization of intrinsic properties.

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Crossover from Mott to Efros-Shklovskii variable-range-hopping conductivity in conducting polyaniline

Cited by 35 publications

References 22 publications

Space‐charge limited conduction in polyaniline films

Space‐charge limited conduction in polyaniline films

Low-temperature electrical anisotropy of self-assembled organic films

Dielectrophoretic placement of quasi‐zero‐, one‐, and two‐dimensional nanomaterials into nanogap for electrical characterizations

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