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Intrinsic electrical conductivity of nanostructured metal-organic polymer chains.

Hermosa C, Vicente Álvarez J, Azani MR, Gómez-García CJ, Fritz M, Soler JM, Gómez-Herrero J, Gómez-Navarro C, Zamora F - Nat Commun (2013)

Bottom Line: This magnitude is preserved for distances as large as 300 nm.We provide the first direct experimental evidence of the gapless electronic structure predicted for these compounds.Our results postulate metal-organic molecular wires as good metallic interconnectors in nanodevices.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Química Inorgánica, Universidad Autónoma de Madrid, Madrid 28049, Spain.

ABSTRACT
One-dimensional conductive polymers are attractive materials because of their potential in flexible and transparent electronics. Despite years of research, on the macro- and nano-scale, structural disorder represents the major hurdle in achieving high conductivities. Here we report measurements of highly ordered metal-organic nanoribbons, whose intrinsic (defect-free) conductivity is found to be 10(4) S m(-1), three orders of magnitude higher than that of our macroscopic crystals. This magnitude is preserved for distances as large as 300 nm. Above this length, the presence of structural defects (~ 0.5%) gives rise to an inter-fibre-mediated charge transport similar to that of macroscopic crystals. We provide the first direct experimental evidence of the gapless electronic structure predicted for these compounds. Our results postulate metal-organic molecular wires as good metallic interconnectors in nanodevices.

No MeSH data available.


Related in: MedlinePlus

Theoretical modelling, anisotropic and disorder media.(a) Normalized resistivity versus length of the sample (in units of Λ) for different values of anisotropy as computed in the 3D resistor model. Black arrows correspond to the EMT result. All the transport regimes described in the main text are depicted in this graph; for small lengths, the resistivity (and resistance) depends exponentially on the sample length, and for larger lengths, it saturates to the value predicted by Effective Medium Theory. The figure also illustrates the importance of high anisotropy in the observation of the different regimes depending on the measured length scale. For the more anisotropic samples, the exponential dependence can be observed for larger lengths. (b) Schematic view of the structure of a MMX crystal showing the polymeric chains and a random distribution of defects (lighter regions).
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f4: Theoretical modelling, anisotropic and disorder media.(a) Normalized resistivity versus length of the sample (in units of Λ) for different values of anisotropy as computed in the 3D resistor model. Black arrows correspond to the EMT result. All the transport regimes described in the main text are depicted in this graph; for small lengths, the resistivity (and resistance) depends exponentially on the sample length, and for larger lengths, it saturates to the value predicted by Effective Medium Theory. The figure also illustrates the importance of high anisotropy in the observation of the different regimes depending on the measured length scale. For the more anisotropic samples, the exponential dependence can be observed for larger lengths. (b) Schematic view of the structure of a MMX crystal showing the polymeric chains and a random distribution of defects (lighter regions).

Mentions: In crystals with lengths L>>Λ, all polymeric chains have at least one defect and, hence, transport perpendicular to the polymer chains becomes determinant. This regime dominates for microscopic samples. To study the transition between the L≤Λ and L >> Λ regimes, we performed extensive numerical simulations in an anisotropic 3D resistor model (Supplementary Note 2 for details). These simulations support the R(L) dependences observed in both the nanoribbons and the crystals (Fig. 4) and confirm that the regime observed in crystals can be understood using the Effective Medium Theory applied to anisotropic systems (Supplementary Note 3)282930. This theory relates effective conductivities, σ//eff and eff, measured in macroscopic crystals, and intrinsic (free of defects) conductivities, σ//int and int, measured using CAFM, where // and indicate the directions parallel and perpendicular to the polymeric chains, respectively. Considering that the only source of disorder is the chain-interrupting defect, we assume that eff=int. With such a limit, high anisotropy and small defect concentration, the effective conductivity decreases to the simple expression σ//eff=eff 0.918/c2 independently of the sample size, as found experimentally. From this expression, we calculate that the defect densities for both crystals and nanoribbons are very similar (0.4%<c<1%), see Supplementary Fig. S5. The simulations also disclose a crossover regime (L≈Λ), which matches the nanoscopic and microscopic regimes. Details about this crossover regime and a simple analytical fit to the numerical data are given in the Supplementary Note 4 and Supplementary Figs S6 and S7.


Intrinsic electrical conductivity of nanostructured metal-organic polymer chains.

Hermosa C, Vicente Álvarez J, Azani MR, Gómez-García CJ, Fritz M, Soler JM, Gómez-Herrero J, Gómez-Navarro C, Zamora F - Nat Commun (2013)

Theoretical modelling, anisotropic and disorder media.(a) Normalized resistivity versus length of the sample (in units of Λ) for different values of anisotropy as computed in the 3D resistor model. Black arrows correspond to the EMT result. All the transport regimes described in the main text are depicted in this graph; for small lengths, the resistivity (and resistance) depends exponentially on the sample length, and for larger lengths, it saturates to the value predicted by Effective Medium Theory. The figure also illustrates the importance of high anisotropy in the observation of the different regimes depending on the measured length scale. For the more anisotropic samples, the exponential dependence can be observed for larger lengths. (b) Schematic view of the structure of a MMX crystal showing the polymeric chains and a random distribution of defects (lighter regions).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3644075&req=5

f4: Theoretical modelling, anisotropic and disorder media.(a) Normalized resistivity versus length of the sample (in units of Λ) for different values of anisotropy as computed in the 3D resistor model. Black arrows correspond to the EMT result. All the transport regimes described in the main text are depicted in this graph; for small lengths, the resistivity (and resistance) depends exponentially on the sample length, and for larger lengths, it saturates to the value predicted by Effective Medium Theory. The figure also illustrates the importance of high anisotropy in the observation of the different regimes depending on the measured length scale. For the more anisotropic samples, the exponential dependence can be observed for larger lengths. (b) Schematic view of the structure of a MMX crystal showing the polymeric chains and a random distribution of defects (lighter regions).
Mentions: In crystals with lengths L>>Λ, all polymeric chains have at least one defect and, hence, transport perpendicular to the polymer chains becomes determinant. This regime dominates for microscopic samples. To study the transition between the L≤Λ and L >> Λ regimes, we performed extensive numerical simulations in an anisotropic 3D resistor model (Supplementary Note 2 for details). These simulations support the R(L) dependences observed in both the nanoribbons and the crystals (Fig. 4) and confirm that the regime observed in crystals can be understood using the Effective Medium Theory applied to anisotropic systems (Supplementary Note 3)282930. This theory relates effective conductivities, σ//eff and eff, measured in macroscopic crystals, and intrinsic (free of defects) conductivities, σ//int and int, measured using CAFM, where // and indicate the directions parallel and perpendicular to the polymeric chains, respectively. Considering that the only source of disorder is the chain-interrupting defect, we assume that eff=int. With such a limit, high anisotropy and small defect concentration, the effective conductivity decreases to the simple expression σ//eff=eff 0.918/c2 independently of the sample size, as found experimentally. From this expression, we calculate that the defect densities for both crystals and nanoribbons are very similar (0.4%<c<1%), see Supplementary Fig. S5. The simulations also disclose a crossover regime (L≈Λ), which matches the nanoscopic and microscopic regimes. Details about this crossover regime and a simple analytical fit to the numerical data are given in the Supplementary Note 4 and Supplementary Figs S6 and S7.

Bottom Line: This magnitude is preserved for distances as large as 300 nm.We provide the first direct experimental evidence of the gapless electronic structure predicted for these compounds.Our results postulate metal-organic molecular wires as good metallic interconnectors in nanodevices.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Química Inorgánica, Universidad Autónoma de Madrid, Madrid 28049, Spain.

ABSTRACT
One-dimensional conductive polymers are attractive materials because of their potential in flexible and transparent electronics. Despite years of research, on the macro- and nano-scale, structural disorder represents the major hurdle in achieving high conductivities. Here we report measurements of highly ordered metal-organic nanoribbons, whose intrinsic (defect-free) conductivity is found to be 10(4) S m(-1), three orders of magnitude higher than that of our macroscopic crystals. This magnitude is preserved for distances as large as 300 nm. Above this length, the presence of structural defects (~ 0.5%) gives rise to an inter-fibre-mediated charge transport similar to that of macroscopic crystals. We provide the first direct experimental evidence of the gapless electronic structure predicted for these compounds. Our results postulate metal-organic molecular wires as good metallic interconnectors in nanodevices.

No MeSH data available.


Related in: MedlinePlus