Semiconducting SWNTs sorted by polymer wrapping:How pure are they?

Short-channel field-effect transistors (FETs) prepared from semiconducting single-walled carbon nanotube (s-SWNT) dispersions sorted with poly(2,5-dimethylidynenitrilo-3,4-didodecylthienylene) are demonstrated. Electrical analysis of the FETs shows no evidence of metallic tubes out of a total number of 646 SWNTs tested, implying an estimated purity of our semiconducting SWNT solution higher than 99.85%. These findings confirm the effectiveness of the polymer-wrapping technique in selecting semiconducting SWNTs, as well as the potential of sorted nanotubes for the fabrication of short channel FETs comprising from 1 to up to 15 nanotubes without inter-nanotube junctions. Published by AIP Publishing

High Performance Ambipolar Field-Effect Transistor of Random Network Carbon Nanotubes

Ambipolar field-effect transistors of random network carbon nanotubes are fabricated from an enriched dispersion utilizing a conjugated polymer as the selective purifying medium. The devices exhibit high mobility values for both holes and electrons (3 cm(2)/V.s) with a high on/off ratio (10(6)). The performance demonstrates the effectiveness of this process to purify semiconducting nanotubes and to remove the residual polymer

Carbon Nanotube Network Ambipolar Field-Effect Transistors with 10(8) On/Off Ratio

Polymer wrapping is a highly effective method of selecting semiconducting carbon nanotubes and dispersing them in solution. Semi-aligned semiconducting carbon nanotube networks are obtained by blade coating, an effective and scalable process. The field-effect transistor (FET) performance can be tuned by the choice of wrapping polymer, and the polymer concentration modifies the FET transport characteristics, leading to a record on/off ratio of 108

Inkjet Printed Single-Walled Carbon Nanotube Based Ambipolar and Unipolar Transistors for High-Performance Complementary Logic Circuits

Inkjet printed single walled carbon nanotubes (SWCNT) field-effect transistors with mobilities of 15 and 7 cm(2) V-1 s(-1) for holes and electrons, respectively, and high on-off ratio, are demonstrated. The high loading of the ink formulation and high electronic quality of the sorted SWCNT enable facile printing of networks displaying high coverage and effective mobility already after a single printing pass. Balanced ambipolarity or mainly unipolar behavior can be tuned by simply varying the number of printing passes, thus enabling the realization of high-performance complementary-like logic gates

Understanding the Selection Mechanism of the Polymer Wrapping Technique toward Semiconducting Carbon Nanotubes

Noncovalent functionalization of single-walled carbon nanotubes (SWNTs) using π-conjugated polymers has become one of the most effective techniques to select semiconducting SWNTs (s-SWNTs). Several conjugated polymers are used, but their ability to sort metallic and semiconducting species, as well as the dispersions yields, varies as a function of their chemical structure. Here, three polymers are compared, namely, poly[2,6-(4,4-bis-(2-dodecyl)-4H-cyclopenta[2,1-b;3,4b′]dithiophene)-alt-4,7(2,1,3-ben-zothiadiazole)] (P12CPDTBT), poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PF12), and poly(3-dodecylthiophene-2,5-diyl) (P3DDT) in their ability to select two types of carbon nanotubes comprising small (≈1 nm) and large (≈1.5 nm) diameters. P12CPDTBT is a better dispersant than PF12 for small diameter nanotubes, while both polymers are good dispersants of large diameter nanotubes. However, these dispersions contain metallic species. P3DDT, instead presents the best overall performance regarding the selectivity toward semiconducting species, with a dispersion yield for s-SWNTs of 15% for small and 21% for large diameter nanotubes. These results are rationalized in terms of electronic and chemical structure showing that: (i) the binding energy is stronger when more alkyl lateral chains adsorb on the nanotube surface; (ii) the binding energy is stronger when the polymer backbone is more flex-ible; (iii) the purity of the dispersions seems to depend on a strong polymer– nanotube interaction

Field-Effect Transistors: Selecting Semiconducting Single-Walled Carbon Nanotubes with Narrow Bandgap Naphthalene Diimide-Based Polymers (Adv. Electron. Mater. 8/2015)

In article number 1500074, Maria Antonietta Loi and co-workers describe a transistor structure where a network of semiconducting single-walled carbon nanotubes connects the source and drain gold electrodes and a naphthalene diimide-based conjugated polymer (PE-N-73) is wrapped around the tubes to keep them individualized. The sparks allocated in the junctions between the tubes in the inside cover image portray the charge hopping from one tube to the other, which is not diminished by the presence of PE-N-73

On-Chip Chemical Self-Assembly of Semiconducting Single-Walled Carbon Nanotubes (SWNTs):Toward Robust and Scale Invariant SWNTs Transistors

In this paper, the fabrication of carbon nanotubes field effect transistors by chemical self-assembly of semiconducting single walled carbon nanotubes (s-SWNTs) on prepatterned substrates is demonstrated. Polyfluorenes derivatives have been demonstrated to be effective in selecting s-SWNTs from raw mixtures. In this work the authors functionalized the polymer with side chains containing thiols, to obtain chemical self-assembly of the selected s-SWNTs on substrates with prepatterned gold electrodes. The authors show that the full side functionalization of the conjugated polymer with thiol groups partially disrupts the s-SWNTs selection, with the presence of metallic tubes in the dispersion. However, the authors determine that the selectivity can be recovered either by tuning the number of thiol groups in the polymer, or by modulating the polymer/SWNTs proportions. As demonstrated by optical and electrical measurements, the polymer containing 2.5% of thiol groups gives the best s-SWNT purity. Field-effect transistors with various channel lengths, using networks of SWNTs and individual tubes, are fabricated by direct chemical self-assembly of the SWNTs/thiolated-polyfluorenes on substrates with lithographically defined electrodes. The network devices show superior performance (mobility up to 24 cm(2) V-1 s(-1)), while SWNTs devices based on individual tubes show an unprecedented (100%) yield for working devices. Importantly, the SWNTs assembled by mean of the thiol groups are stably anchored to the substrate and are resistant to external perturbation as sonication in organic solvents

Effect of temperature on the selection of semiconducting single walled carbon nanotubes using Poly(3-dodecylthiophene-2,5-diyl)

We report on the investigation of the temperature effect on the selective dispersion of single-walled carbon nanotubes (SWNTs) by Poly(3-dodecylthiophene-2,5-diy1) wrapping. The interaction mechanism between polymer chains and SWNTs is studied by controlling the polymer aggregation via variation of the processing temperature. Optical absorption and photoluminescence measurements including time resolved photoluminescence spectroscopy are employed to study the degree of interaction between the polymer in different aggregation states and the carbon nanotubes. At low processing temperatures, results are consistent with the planarization of the polymer chains and with SWNTs working as seeds for polymer aggregation. The formation of small clusters due to the inter-digitation of alkyl tails between neighboring polymer-wrapped SWNTs allows the formation of the SWNT bundles, as experimentally evidenced and investigated by molecular dynamics simulations. The interaction between the tubes within the bundles, which is reflected in the variation of the photoluminescence dynamics of the polymer, can be suppressed by warming up the sample. (C) 2014 Elsevier Ltd. All rights reserved

Understanding the Selection Mechanism of the Polymer Wrapping Technique toward Semiconducting Carbon Nanotubes

Noncovalent functionalization of single-walled carbon nanotubes (SWNTs) using π-conjugated polymers has become one of the most effective techniques to select semiconducting SWNTs (s-SWNTs). Several conjugated polymers are used, but their ability to sort metallic and semiconducting species, as well as the dispersions yields, varies as a function of their chemical structure. Here, three polymers are compared, namely, poly[2,6-(4,4-bis-(2-dodecyl)-4H-cyclopenta[2,1-b;3,4b′]dithiophene)-alt-4,7(2,1,3-ben-zothiadiazole)] (P12CPDTBT), poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PF12), and poly(3-dodecylthiophene-2,5-diyl) (P3DDT) in their ability to select two types of carbon nanotubes comprising small (≈1 nm) and large (≈1.5 nm) diameters. P12CPDTBT is a better dispersant than PF12 for small diameter nanotubes, while both polymers are good dispersants of large diameter nanotubes. However, these dispersions contain metallic species. P3DDT, instead presents the best overall performance regarding the selectivity toward semiconducting species, with a dispersion yield for s-SWNTs of 15% for small and 21% for large diameter nanotubes. These results are rationalized in terms of electronic and chemical structure showing that: (i) the binding energy is stronger when more alkyl lateral chains adsorb on the nanotube surface; (ii) the binding energy is stronger when the polymer backbone is more flex-ible; (iii) the purity of the dispersions seems to depend on a strong polymer– nanotube interaction