Carbon Nanotube Wires Research Articles

CMOS LC voltage controlled oscillator design using multiwalled and single-walled carbon nanotube wire inductors

We have utilized our Multiwalled Carbon NanoTube (MWCNT) and Single-Walled Carbon NanoTube (SWCNT) bundle interconnects model in a widely used π model to study the performances of MWCNT and SWCNT bundle wire inductors and compared these with copper (Cu) inductors. The calculation results show that the Q-factors of Carbon NanoTube (CNT) wire (SWCNT bundle and MWCNT) inductors are higher than that of the Cu wire inductor. This is mainly due to much lower resistance of CNT and negligible skin effect in carbon nanotubes at higher frequencies. The application of CNT wire inductor in LC VCO is also studied and the Cadence/Spectre simulations show that VCOs with CNT bundle wire inductors have significantly improved performance such as the higher oscillation frequency and lower phase noise due to their smaller resistances and higher Q-factors. It is also noticed that CMOS LC VCO using a SWCNT bundle wire inductor has better performance when compared with the performance of LC VCO using the MWCNT wire inductor due to its lower resistance and higher Q-factor.

Failure analysis of carbon nanotube wires

A failure analysis of four carbon nanotube (CNT) wires comprised of 1-, 30-, 60-, and 100-yarns was conducted when subjected to constant tension and cyclic tension–tension loading conditions. Each wire had different controlling mechanisms of failure. Tensile and cyclic load-induced failures were related to the movement within yarns and/or among yarns in the CNT wires. The 1-yarn CNT wire exhibited a ductile fracture when constant tensile load was applied; recoverable deformation bands were observed on bending and straightening. The 30-yarn CNT wire showed a variant/independent fibrillar failure under constant tensile loading condition, while it failed by biaxial rotation, bend and twist under cyclic loading condition. The 60-yarn CNT wire resulted in a stake and socket fibre fracture when loaded to failure in constant tension; however, in the cyclic loading condition, the wire failed by kink band process. The 100-yarn wire failure mechanism was controlled by the surface wear in both constant tension and fatigue loading conditions. This failure analysis study presents detailed fracture surface features that can be used to diagnose the cause of failure, develop failure mechanisms, and improve the properties of CNT wires when used in real-life applications.

Influence of nanoparticle size to the electrical properties of naphthalenediimide on single-walled carbon nanotube wiring

Nanoparticles of N,N′-bis(n-alkyl)tetracarbonatenaphthalenediimide (NDI) were adsorbed on single-walled carbon nanotube (SWNT) wires dispersed on a SiO2 substrate. The electrical properties were measured along the long axis of the SWNTs, and in all cases through the nanoparticles showed rectification in semiconducting I–V curve. The plateau width of the I–V curve through the NDI nanoparticles on metallic SWNTs decreased as the particle size increased, while the rectification ratio increased. The conduction mechanism was changed from tunneling conduction to Schottky-like conduction and their boundary is at about 3 nm diameter.

Theoretical study of current-voltage characteristics of carbon nanotube wire functionalized with hydrogen atoms

A functionalized single-walled carbon nanotube (SWCNT) of a finite length with a ring-like hydrogenation around its surface is designed toward fabrication of a molecular field-effect transistor (FET) device. The molecular wire thus designed is equipped with a quantum dot inside, which is confirmed by theoretical analysis for electronic transport. In particular, the current-voltage (I–V) characteristics under influence of the gate voltage are discussed in detail.

Tensile loading behavior of carbon nanotube wires

The mechanical behavior of four carbon nanotube (CNT) wires, comprised of 1-yarn, 30-yarn, 60-yarn, and 100-yarn, was investigated under constant tension at two loading rates of 0.02mm/s and 2mm/s. Tests were conducted with both as-fabricated and pre-stressed wires. The ultimate tenacity or apparent ultimate tensile strength of all four wires was found to be independent of loading rate, with those for the single-yarn wire about twice those of the multiple-yarn wires. Strain at a given stress level and failure strain of the multiple-yarn wires before pre-stressing were almost an order of magnitude larger than those for the single-yarn wire, and this difference was reduced considerably after pre-stressing. The failure mechanisms of 1-yarn wire or twisted individual yarns in multiple-strand wires involved ductile (necking) deformation and fibrillar breakage. Inner yarns in multiple-yarn wires initially failed at the same location, followed by outer yarns failing at different locations. Additionally, sliding occurred between individual yarns, and twisting of the yarns accompanied by surface wear took place in the multiple-yarn wires, which contributed to their failure at a lower load compared to the single-yarn wire.

Carbon Nanotube Wiring of Donor–Acceptor Nanograins by Self‐Assembly and Efficient Charge Transport

Grain wiring: Functionalized single-wall carbon nanotube wiring between the nanograins of porphyrin (donor)-C60 (acceptor) dyads results in efficient charge transport between them, leading to the highest incident photon-to-current efficiency (22 %) ever reported for analogous photoelectrochemical devices utilizing donor-acceptor linked dyads.

Carbon Nanotube Wiring of Donor–Acceptor Nanograins by Self‐Assembly and Efficient Charge Transport

Leitend verbunden: Funktionalisierte einwandige Kohlenstoffnanoröhren als Verknüpfung zwischen Nanokörnern aus Porphyrin(Donor)-C60(Akzeptor)-Diaden ermöglichen einen effizienten Ladungstransport und führen zur höchsten Photon-Strom-Umwandlungseffizienz (22 %), die je für entsprechende photoelektrochemische Funktionseinheiten mit Donor-Akzeptor-Diaden gemessen wurde.

Carbon nanotube wires and cables: Near-term applications and future perspectives

Wires and cables are essential to modern society, and opportunities exist to develop new materials with reduced resistance, mass, and/or susceptibility to fatigue. This article describes how carbon nanotubes (CNTs) offer opportunities for integration into wires and cables for both power and data transmission due to their unique physical and electronic properties. Macroscopic CNT wires and ribbons are presently shown as viable replacements for metallic conductors in lab-scale demonstrations of coaxial, USB, and Ethernet cables. In certain applications, such as the outer conductor of a coaxial cable, CNT materials may be positioned to displace metals to achieve substantial benefits (e.g. reduction in cable mass per unit length (mass/length) up to 50% in some cases). Bulk CNT materials possess several unique properties which may offer advantages over metallic conductors, such as flexure tolerance and environmental stability. Specifically, CNT wires were observed to withstand greater than 200,000 bending cycles without increasing resistivity. Additionally, CNT wires exhibit no increase in resistivity after 80 days in a corrosive environment (1 M HCl), and little change in resistivity with temperature (<1% from 170-330 K). This performance is superior to conventional metal wires and truly novel for a wiring material. However, for CNTs to serve as a full replacement for metals, the electrical conductivity of CNT materials must be improved. Recently, the conductivity of a CNT wire prepared through simultaneous densification and doping has exceeded 1.3 × 10(6) S/m. This level of conductivity brings CNTs closer to copper (5.8 × 10(7) S/m) and competitive with some metals (e.g. gold) on a mass-normalized basis. Developments in manipulation of CNT materials (e.g. type enrichment, doping, alignment, and densification) have shown progress towards this goal. In parallel with efforts to improve bulk conductivity, integration of CNT materials into cabling architectures will require development in electrical contacting. Several methods for contacting bulk CNT materials to metals are demonstrated, including mechanical crimping and ultrasonic bonding, along with a method for reducing contact resistance by tailoring the CNT-metal interface via electroless plating. Collectively, these results summarize recent progress in CNT wiring technologies and illustrate that nanoscale conductors may become a disruptive technology in cabling designs.

High conductivity carbon nanotube wires from radial densification and ionic doping

Application of drawing dies to radially densify sheets of carbon nanotubes (CNTs) into bulk wires has shown the ability to control electrical conductivity and wire density. Simultaneous use of KAuBr4 doping solution, during wire drawing, has led to an electrical conductivity in the CNT wire of 1.3×106 S/m. Temperature-dependent electrical measurements show that conduction is dominated by fluctuation-assisted tunneling, and introduction of KAuBr4 significantly reduces the tunneling barrier between individual nanotubes. Ultimately, the concomitant doping and densification process leads to closer packed CNTs and a reduced charge transfer barrier, resulting in enhanced bulk electrical conductivity.

Performance Modeling for Single- and Multiwall Carbon Nanotubes as Signal and Power Interconnects in Gigascale Systems

Using physics-based circuit models, the performances of carbon nanotube (CNT) interconnects, both single- and multiwall (SWNT and MWNT), are benchmarked against their copper counterparts at a realistic operating temperature (100degC). The models used capture various electron phonon scattering mechanisms and the dependence of quantum conductance on temperature and diameter. It is demonstrated that any performance comparison between CNT and copper wires needs to be done at realistic temperatures because changes in temperature affect copper and CNT interconnects quite differently. The results of this paper demonstrate that a hybrid system of copper/SWNT/MWNT offers the highest performance enhancement for interconnects.

On-Chip Electrical Breakdown of Metallic Nanotubes for Mass Fabrication of Carbon-Nanotube-Based Electronic Devices

A mass fabrication scheme for carbon-nanotube (CNT)-based electronic devices is developed by combining the semiconductor wafer electrical sorting with selective burning of metallic CNT wires. By applying a millisecond electrical pulse to CNTs with the optimized logical scheme of voltage stress, we successfully removed the metallic CNTs but not the high-performance semiconductor CNTs. The fabrication scheme implemented with a probe card achieved a 100 % gross yield of CNT-based sensors with a short process time.

Performance Comparisons Between Cu/Low-$\kappa$, Carbon-Nanotube, and Optics for Future On-Chip Interconnects

In this letter, we compare the performance of carbon nanotubes and optical interconnects with the scaled Cu/Iow-kappa interconnects for future high-performance integrated circuits. We present these comparisons in terms of both commonly used metrics, such as latency, energy per bit (power dissipation), as well as by demonstrating an explicit relationship between system-relevant metrics such as bandwidth density, power density and latency. We find that for long wires (~10 mm) both carbon nanotubes and optical interconnects outperform future Cu wires with optical interconnects having lower energy per bit and latency. For short wires (~1 mm), carbon-nanotube wires outperform both Cu and optical interconnects.

Cold linear cathodes with carbon nanotube emitters and their application in luminescenttubes

We introduce an efficient method of fabricating cold, linear cathodes with carbonnanotube (CNT) emitters. A nickel wire was painted first with silver paste, thenwith CNT paste. After sintering under nitrogen and activation by adhesivetape, the cathode wire provided a stable and homogeneous emission density of200 mA cm−2 at6.2 V µm−1. As an application, luminescent tubes were constructed using this CNT wire as thecathode and a transparent CNT film as the anode. These cold cathodes can replaceconventional hot cathodes, which are widely used in vacuum electronic devices. The noveltwo-layer structure can be applied to any substrate, and is simple and inexpensive tofabricate.

Hot filament chemical vapour deposition processing of titanate nanotube coatings

In the present paper, we report on the processing of titanate nanotubes using the hotfilament chemical vapour deposition (HF-CVD) method to synthesize titania–carbonnanotube–wire composites. The titanate nanotubes are prepared using a chemical route,and then deposited on silicon using an electrodeposition method. The HF-CVD is used to process these coatingsat different temperatures in vacuum as well as in different concentrations of hydrogen(H2) andmethane (CH4) gas mixtures. The evolutions of the surface and precipitation for variousphases have been monitored using different characterization techniques.It is observed that titanate nanotubes start disintegrating aboveTs∼500 °C, and exhibit different types of phase precipitation depending upon the temperature andgas ambient. Under appropriate conditions, the presence of activated hydrogen and carbonradicals leads to the formation of novel architectures of mixtures of nanophases such ascarbide, nonstoichiometric titania, carbon nanotubes, and titania decorated carbonnanowires. The results are discussed in terms of reduction in the thermal reaction barrierdue to the presence of atomic hydrogen, and the formation of energetic sites duringdisintegration of titania nanotubes to facilitate nucleation of nanotube and nanowirestructures.

Conductance of carbon nanotubes with disorder: A numerical study

We study the conductance of carbon nanotube wires in the presence of disorder, in the limit of phase coherent transport. For this purpose, we have developed a simple numerical procedure to compute transmission through carbon nanotubes and related structures. Two models of disorder are considered, weak uniform disorder and isolated strong scatterers. In the case of weak uniform disorder, our simulations show that the conductance is not significantly affected by disorder when the Fermi energy is close to the band center. Further, the transmission around the band center depends on the diameter of these zero bandgap wires. We also find that the calculated small bias conductance as a function of the Fermi energy exhibits a dip when the Fermi energy is close to the second subband minima. In the presence of strong isolated disorder, our calculations show a transmission gap at the band center, and the corresponding conductance is very small.