Ambipolar Conversion of Polymer-Coated All Single-Walled Carbon Nanotube Field-Effect Transistors (original) (raw)
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Scientific Reports, 2016
Printing electronics has become increasingly prominent in the field of electronic engineering because this method is highly efficient at producing flexible, low-cost and large-scale thin-film transistors. However, TFTs are typically constructed with rigid insulating layers consisting of oxides and nitrides that are brittle and require high processing temperatures, which can cause a number of problems when used in printed flexible TFTs. In this study, we address these issues and demonstrate a method of producing inkjet-printed TFTs that include an ultra-thin polymeric dielectric layer produced by initiated chemical vapor deposition (iCVD) at room temperature and highly purified 99.9% semiconducting carbon nanotubes. Our integrated approach enables the production of flexible logic circuits consisting of CNT-TFTs on a polyethersulfone (PES) substrate that have a high mobility (up to 9.76 cm 2 V −1 sec − 1), a low operating voltage (less than 4 V), a high current on/off ratio (3 × 10 4), and a total device yield of 90%. Thus, it should be emphasized that this study delineates a guideline for the feasibility of producing flexible CNT-TFT logic circuits with high performance based on a low-cost and simple fabrication process. Printable flexible electronics is considered as one of the most rapidly developing technologies because it has the potential to be scalable and cost-effective 1-5. In particular, printed thin-film transistors (TFTs) that utilize carbon nanotubes (CNTs) have exhibited high on-state currents, mobility, and current on/off ratios at low operating voltages. These CNT-TFTs have been fabricated by various printing techniques, such as roll-to-roll gravure 6,7 , aerosol jet 8-10 , and screen printing 11. However, the roll-to-roll gravure and aerosol jet printing processes present challenges because the high roughness of the resulting layers limits the precision in patterning electrodes 6,7. In addition, the reported screen printing process presented inherent issues, such as a thick printed layer, because it requires ink with high viscosity 11. Therefore, the reported CNT-TFTs produced using the aforementioned methods resulted in low carrier mobility and correspondingly high operating voltages 6,7,11. On the other hand, the inkjet printing technique may be the most promising alternative because of its mask-less process, high printing resolution, and low-temperature requirement 12-19. Therefore, a number of studies on the inkjet-printed CNT-TFTs based on various gate dielectric layers, such as ion-gel materials 9,12,13 , barium titanate (BaTiO3-BTO) nanoparticles 6,11,14 , and polymethyl methacrylate (PMMA) 15 , have been extensively reported. However, these dielectric layers have several additional constraints, including an increased thickness, low dielectric constant, pinholes, and solvent residues, which inevitably necessitate high operation voltage and deteriorate device yield. To address the aforementioned concerns, we previously reported the preparation of poly(1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane) (pV3D3) via a one-step, solvent-free technique called 'initiated chemical vapor
Journal of Nanoscience and Nanotechnology, 2011
We have successfully fabricated nanometer-scale carbon nanotube field effect transistors (CNT FETs) on a flexible and transparent substrate by electron-beam lithography. The measured currentvoltage data show good hole conduction FET characteristics, and the on/off ratio of the current is more than 10 2. The conductance (as well as current) systematically decreases with the increase of the strain, suggesting that the bending of the substrate still affects the deformation condition of the short channel CNT FETs.
Controlled Assembly of Highly Density SWNT Networks on a Flexible Parylene-C Substrate
2008
In this paper, we present a directed assembly technique for controlled micro-patterning of Single-Walled Carbon Nanotubes (SWNTs) on a flexible parylene-C substrate for electronic applications. The presented large scale fabrication of ordered carbon nanotube arrays and networks is achieved by performing site-selective fluidic assembly of SWNTs on a plasma treated parylene-C substrate. Parylene-C, which is lightweight, mechanically strong and stress-free material deposited at room temperature, is an emerging substrate material for flexible devices. The uniformly deposited nanotube lateral structures are formed directly on the parylene-C substrate without utilizing printing or transfer techniques. Both electrical and structural characterizations are performed on the SWNTbased devices on the flexible substrate. The developed nanotube patterning on polymeric substrates has immediate applications in wearable electronics and sensors, flexible field effect transistors (FETs) and lateral in...
Advanced Functional …, 2006
The possibility of using random networks or aligned arrays of single-walled carbon nanotubes (SWNTs) as semiconducting or conducting thin-film-type materials in the emerging field of flexible and large-area electronics has recently attracted some attention. The unique electrical, mechanical, and thermal properties of SWNTs, as demonstrated pri-marily through studies of single-tube devices such as transistors, solar cells, logic gates, and ring oscillators, make SWNTs a potentially attractive building block for thin-film devices. The absence of dangling bonds makes it possible for SWNTs to exhibit good electrical characteristics on a wide range of substrates, including plastics. This feature, combined with the ability to print the tubes at room temperature using dry transfer processes or solution casting make SWNT films potentially attractive for large-area and flexible electronics. Recent reports demonstrate that thin-film field-effect transistors (FETs) based on random networks of SWNTs can be successfully fabricated on plastic substrates, and that the resulting devices can achieve good electrical, mechanical, and even optical (e.g., transparency) properties. Several major challenges must be overcome, however, in order to take full advantage of SWNT films for these applications. First, since as-grown carbon nanotubes are mixtures of metallic tubes and semiconducting tubes, it is necessary to be able to grow semiconducting tubes only, perhaps by selective catalysis or by plasma-enhanced chemical vapor deposition (CVD), or to remove metallic tubes, perhaps by electrical breakdown or chemical functionalization. Several groups are working on these and related approaches, as they relate to applications of SWNTs in thin-film electronics as well as many other application areas. A second challenge, which is mainly related to active device applications, involves the development of materials for gate dielectrics that can be used to achieve high-performance n-and p-channel operation in SWNT TFTs, with low hysteresis, good mechanical properties, and compatibility for low-temperature plastic substrates.
ACS Nano, 2010
We have characterized the previously undescribed parameters for engineering the electrical properties of single-walled carbon nanotube (SWCNT) films for technological applications. First, the interfacial tension between bare SWCNT network films and a top coating passivation material was shown to dictate the variability of the films' sheet resistance (R s ) after application of the top coating. Second, the electrical stability of the coated SWCNT films was affected by the mismatch between the CTE of the supporting substrate and the SWCNT network film. An upshift in the Raman G-band spectrum of SWCNTs on bare PET suggested that compressive strain was induced by the CTE mismatch after heating and cooling. These findings provide important guidelines for the choice of substrate and passivation coating materials that promote environmental stability in SWCNT-based transparent conductive films.
Transparent and Flexible Carbon Nanotube Transistors
Nano Letters, 2005
We report the fabrication of transparent and flexible transistors where both the bottom gate and the conducting channel are carbon nanotube networks of different densities and Parylene N is the gate insulator. Device mobilities of 1 cm 2 V-1 s-1 and on/off ratios of 100 are obtained, with the latter influenced by the properties of the insulating layer. Repetitive bending has minor influence on the characteristics, with full recovery after repeated bending. The operation is insensitive to visible light and the gating does not influence the transmission in the visible spectral range.
Fully Printed, High Performance Carbon Nanotube Thin-Film Transistors on Flexible Substrates
Nano Letters, 2013
Fully printed transistors are a key component of ubiquitous flexible electronics. In this work, the advantages of an inverse gravure printing technique and the solution processing of semiconductor-enriched single-walled carbon nanotubes (SWNTs) are combined to fabricate fully printed thin-film transistors on mechanically flexible substrates. The fully printed transistors are configured in a top-gate device geometry and utilize silver metal electrodes and an inorganic/ organic high-κ (∼17) gate dielectric. The devices exhibit excellent performance for a fully printed process, with mobility and on/off current ratio of up to ∼9c m 2 /(V s) and 10 5 , respectively. Extreme bendability is observed, without measurable change in the electrical performance down to a small radius of curvature of 1 mm. Given the high performance of the transistors, our high-throughput printing process serves as an enabling nanomanufacturing scheme for a wide range of large-area electronic applications based on carbon nanotube networks.