title: Nanoscale Charge Percolation Analysis in Polymer-Sorted (7,5) Single-Walled Carbon Nanotube Networks.
abstract: The current percolation in polymer-sorted semiconducting (7,5) single-walled carbon nanotube (SWNT) networks, processed from solution, is investigated using a combination of electrical field-effect measurements, atomic force microscopy (AFM), and conductive AFM (C-AFM) techniques. From AFM measurements, the nanotube length in the as-processed (7,5) SWNTs network is found to range from ≈100 to ≈1500 nm, with a SWNT surface density well above the percolation threshold and a maximum surface coverage ≈58%. Analysis of the field-effect charge transport measurements in the SWNT network using a 2D homogeneous random-network stick-percolation model yields an exponent coefficient for the transistors OFF currents of 16.3. This value is indicative of an almost ideal random network containing only a small concentration of metallic SWNTs. Complementary C-AFM measurements on the other hand enable visualization of current percolation pathways in the xy plane and reveal the isotropic nature of the as-spun (7,5) SWNT networks. This work demonstrates the tremendous potential of combining advanced scanning probe techniques with field-effect charge transport measurements for quantification of key network parameters including current percolation, metallic nanotubes content, surface coverage, and degree of SWNT alignment. Most importantly, the proposed approach is general and applicable to other nanoscale networks, including metallic nanowires as well as hybrid nanocomposites.
authors.affiliation: Department of Physics and Centre for Plastic Electronics, Imperial College London, SW7 2BW, London, UK.
authors.forename: Francesca
authors.initials: F
authors.lastname: Bottacchi
authors.affiliation: Independent Consultant, via don Gnocchi 33, 20148, Milan, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Bottacchi
authors.affiliation: Institute of Physical and Theoretical Chemistry, Faculty of Chemistry and Pharmacy, Julius-Maximilian University Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Späth
authors.affiliation: Institute of Physical and Theoretical Chemistry, Faculty of Chemistry and Pharmacy, Julius-Maximilian University Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Imge
authors.initials: I
authors.lastname: Namal
authors.affiliation: Institute of Physical and Theoretical Chemistry, Faculty of Chemistry and Pharmacy, Julius-Maximilian University Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Hertel
authors.affiliation: Department of Physics and Centre for Plastic Electronics, Imperial College London, SW7 2BW, London, UK.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Anthopoulos
keywords: carbon nanotubes; conductive atomic force microscopy; network percolation; surface characterization; transistors