Transport in polyaniline near the critical regime of the metal-insulator transition

Menon, Reghu; Yoon, C.O.; Moses, D.; Heeger, Alan J.; Cao, Yong

doi:10.1103/physrevb.48.17685

Cited by 208 publications

(109 citation statements)

References 27 publications

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“…This illustrates that our system is quasi two-dimensional (quasi-2D), as expected from the reduced thickness of our polymer thin film (25-30 nm), which is of the order of estimated coherence length in the 10 nm range for highly doped polymers. 8 Figure 2(b) shows that samples 5 and 6 follow a power law dependence of the conductivity, as expected for a conductor in the so-called critical regime, 1 i.e., approaching the metallic side of a M-I transition…”

Section: 5supporting

confidence: 58%

“…This strongly suggests that these two samples are at the onset of metallic state, with metallicity fully established when b < 0.33. 1,16 The normalized plot in Figure 2(c) emphasizes the transition from convex conductivity versus temperature curves for insulating-type samples, to concave curves found for highly conductive samples. This relates to the change of the second derivative r 00 (T) sign when moving from the insulator towards the transition to the metallic side, as deduced from Eqs.…”

Section: 5mentioning

confidence: 89%

“…Metallicity in polymers dates from the discovery of high-conductivity in chemical-doped polymeric materials. 1,2 Its experimental evidence has however remained elusive, as a hopping conduction mechanism prevails at low temperatures. The lack of a long range crystalline order gives rise to localisation of the electron wave functions and makes the thermally assisted hopping between localized states dominate over the diffusive motion through delocalized states expected in a band-like transport regime.…”

mentioning

confidence: 99%

“…The lack of a long range crystalline order gives rise to localisation of the electron wave functions and makes the thermally assisted hopping between localized states dominate over the diffusive motion through delocalized states expected in a band-like transport regime. 3 Very few counterexamples have been reported in chemically highly doped polyaniline 1,4,5 or polypyrrole bulk materials.…”

mentioning

confidence: 99%

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Magnetoconductance anisotropy of a polymer thin film at the onset of metallicity

Zanettini

Dayen

Etrillard

et al. 2015

Applied Physics Letters

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Thin films of poly(2,5-bis(3-dodecyl-2-yl)-thieno[3,2-b]thiophene) (C12-PBTTT) polymer under electrolyte gating and doping are investigated as model systems for organic thin films devices approaching the metallic side of a metal-insulator (M-I) transition. For the most doped samples, with an estimated density reaching 8 × 1020 cm−3 holes and a conductivity exceeding 1000 S cm−1, a positive high-field magnetoconductance is found in a limited temperature range window and only when the field is perpendicular to the sample plane. This signature of weak localization, combined with indications of finite zero-temperature conductivity, allows us to identify delocalized metallic-like transport in these thin films, even though the conductivity decreases when cooling down the samples.

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Section: 5supporting

confidence: 58%

Section: 5mentioning

confidence: 89%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Magnetoconductance anisotropy of a polymer thin film at the onset of metallicity

Zanettini

Dayen

Etrillard

et al. 2015

Applied Physics Letters

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“…In fact, it is only in a limited number of cases (for example, free-standing thick films of semiconducting polymers such as polyaniline (for example, refs 11 and 12) or polypyrrole (for example, ref. 13)) that chemical doping can delocalize carrier wavefunctions to the point of inducing an insulator-metal transition to a state with finite conductivity as T-0, or even entering the weakly localized regime beyond it 12,13 . It is currently unclear whether a metallic state is possible only in certain semiconducting polymers, or whether efficacy of chemical doping, or minimization of disorder, limit delocalization of the charge carriers.…”

mentioning

confidence: 99%

Hopping transport and the Hall effect near the insulator–metal transition in electrochemically gated poly(3-hexylthiophene) transistors

et al. 2012

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Despite 35 years of investigation, much remains to be understood regarding charge transport in semiconducting polymers, including the ultimate limits on their conductivity. Recently developed ion gel gating techniques provide a unique opportunity to study such issues at very high charge carrier density. Here we have probed the benchmark polymer semiconductor poly(3-hexylthiophene) at electrochemically induced three-dimensional hole densities approaching 10 21 cm À 3 (up to 0.2 holes per monomer). Analysis of the hopping conduction reveals a remarkable phenomenon where wavefunction delocalization and Coulomb gap collapse are disrupted by doping-induced disorder, suppressing the insulator-metal transition, even at these extreme charge densities. Nevertheless, at the highest dopings, we observe, for the first time in a polymer transistor, a clear Hall effect with the expected field, temperature and gate voltage dependencies. The data indicate that at such mobilities (B0.8 cm 2 V À 1 s À 1 ), despite the extensive disorder, these polymers lie close to a regime of truly diffusive band-like transport.

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Electrical resistivity and magnetoresistivity of protonic acid (h2SO4 and HCl)-doped polyaniline at low temperature

Ghosh

Barman

Meikap

et al. 2000

J. Appl. Polym. Sci.

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Electrical-transport properties of protonic acid (H 2 SO 4 and HCl)-doped polyaniline (PANI) in an aqueous ethanol medium were investigated in the temperature range 1.8 K Յ T Յ 300 K and in a magnetic field up to 8 T. The room-temperature resistivity of HCl-doped PANI is larger than that of H 2 SO 4 -doped PANI. The resistivity ratios r ϭ (1.8 K)/(300 K) of the samples are high. The samples in the insulating region show a crossover from a Mott to an Efros-Shklovskii variable range hopping conduction at T ϭ 9.8 K for H 2 SO 4 -doped PANI and 8.5 K for HCl-doped PANI. The magnetoresistivity of these samples is also explained by the variable range hopping theory. The different physical parameters were calculated from the experimental data.

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Transport in polyaniline near the critical regime of the metal-insulator transition

Cited by 208 publications

References 27 publications

Magnetoconductance anisotropy of a polymer thin film at the onset of metallicity

Magnetoconductance anisotropy of a polymer thin film at the onset of metallicity

Hopping transport and the Hall effect near the insulator–metal transition in electrochemically gated poly(3-hexylthiophene) transistors

Electrical resistivity and magnetoresistivity of protonic acid (h2SO4 and HCl)-doped polyaniline at low temperature

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