Stable metal-CNT contacts using shadow mask technique for CNTFET fabrication
23 Jul 2018-Vol. 1989, Iss: 1, pp 030002
TL;DR: In this paper, a new approach based on silicon shadow mask has been reported to realize metal-carbon nanotubes (CNTs) contacts in end-contact configuration, which provides low-ohmic and stable contacts than that of side-contacted configuration.
Abstract: In this paper a new approach based on silicon shadow mask has been reported to realize metal-carbon nanotubes (CNTs) contacts in end-contact configuration, which provides low-ohmic and stable contacts than that of side-contacted configuration The source and drain contacts were fabricated by placing the fabricated silicon shadow mask over the single walled CNTs (SWNTs) coated wafer followed by deposition of Cr/Au∼100nm/500 nm using e-beam evaporation The SEM image clearly shows the end-contacts of individual SWNTs with the gold electrodes Further, Keithley SCS 4200 parameter analyzer was used to perform electrical characterization of the fabricated devices The calculated ION/IOFF ratio and threshold voltage of the typically shown device are ∼120 and∼290 mV respectively
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TL;DR: In this paper, the effect of thickness of gate dielectric on the performance of CNFETs was analyzed. And the results showed that as the thickness of the gate dieslectric decreases, drain current increases.
Abstract: In this paper we presented the analysis of Carbon Nanotube Field Effect Transistors (CNFETs) using various high- k gate dielectric materials. The objective of this work was to choose the best possible material for gate dielectric. This paper also presented the study on the effect of thickness of gate dielectric on the performance of the device. For the analysis (19, 0) CNT was considered because the diameter of (19, 0) CNT is 1.49nm and the CNFETs have been fabricated with the CNT diameter of ~1.5nm. It has been observed that La 2 O 3 is the best gate dielectric material followed by HfO 2 and ZrO 2 . It was also observed that as thickness of gate dielectric material reduces, drain current of CNFET increases. The outcomes of this study matches with the analytical results and hence confirm the results
5 citations
Cites background from "Stable metal-CNT contacts using sha..."
...Commonly reported high-k dielectrics include Hafnium oxide (HfO2), Alumina (Al2O3), Hafnium Silicate (HfSiO4), Zirconia (ZrO2), Yttrium Oxide (Y2O3), Lanthanum oxide (La2O3), Silicon dioxide (SiO2) and Silicon Nitride (Si3N4) [6-15]....
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01 Jan 2021
TL;DR: In this article, the authors discuss different device structures of CNFETs, steps involved in the fabrication of CNT-based field effect transistors, advantages and limitations of various methods involved in synthesizing CNTs, conduction models, and performance parameters.
Abstract: The problems associated with attempting to scale down traditional metal oxide field-effect transistors (MOSFET) have led researchers to look into CNT-based field-effect transistors (CNFETs), as an alternative. Though the scaling of MOSFET has been the driving force toward the technological advancement, but due to continuous scaling, various secondary effects which include short channel effects, high leakage current, excessive process variation, and reliability issues degrade the device performance. On the other hand, CNFETs are not subjected to the scaling problems. The operation principle of the CNFET is similar to traditional MOSFET but the conduction phenomena are different. The traditional MOSFETs are based on the drift and diffusion phenomena in which channel length is very large as compared to mean free path of charge carriers whereas the CNFETs are based on ballistic transport conduction mechanism, in which channel length is very small as compared to mean free path of charge carriers. In CNFET, electrons are injected from source to drain and transported through the nanotubes without scattering. Due to ballistic transport the nanotubes act as a perfect conductor for electrons such that the full quantum information of these electrons (momentum, energy, spin) can be transferred without losses. The channel current in CNFETs depends on gate voltage, number of nanotubes in channel, dielectric material and its thickness, and diameter and chirality of carbon nanotubes. So in this chapter we shall discuss different device structures of CNFET, steps involved in the fabrication of CNFETs, advantages and limitations of various methods involved in the synthesis of CNTs, conduction models, and performance parameters.
2 citations
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TL;DR: In this article, the authors describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency.
Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.
26,457 citations
TL;DR: In this paper, the fabrication of a three-terminal switching device at the level of a single molecule represents an important step towards molecular electronics and has attracted much interest, particularly because it could lead to new miniaturization strategies in the electronics and computer industry.
Abstract: The use of individual molecules as functional electronic devices was first proposed in the 1970s (ref 1) Since then, molecular electronics2,3 has attracted much interest, particularly because it could lead to conceptually new miniaturization strategies in the electronics and computer industry The realization of single-molecule devices has remained challenging, largely owing to difficulties in achieving electrical contact to individual molecules Recent advances in nanotechnology, however, have resulted in electrical measurements on single molecules4,5,6,7 Here we report the fabrication of a field-effect transistor—a three-terminal switching device—that consists of one semiconducting8,9,10 single-wall carbon nanotube11,12 connected to two metal electrodes By applying a voltage to a gate electrode, the nanotube can be switched from a conducting to an insulating state We have previously reported5 similar behaviour for a metallic single-wall carbon nanotube operated at extremely low temperatures The present device, in contrast, operates at room temperature, thereby meeting an important requirement for potential practical applications Electrical measurements on the nanotube transistor indicate that its operation characteristics can be qualitatively described by the semiclassical band-bending models currently used for traditional semiconductor devices The fabrication of the three-terminal switching device at the level of a single molecule represents an important step towards molecular electronics
5,258 citations
TL;DR: In this article, the authors summarized the recent progresses on the development of high-performance supercapacitors based on carbon nanomaterials and provided various rational concepts for materials engineering to improve the device performance for a large variety of potential applications.
567 citations
TL;DR: Results of the study showed that 100% of lead was removed by using COOH-MCNTs at pH 7, 150 rpm, and 2 hours, likely attributed to the strong affinity of lead to the physical and chemical properties of the CNTs.
Abstract: The adsorption mechanism of the removal of lead from water by using carboxylic functional group (COOH) functionalized on the surface of carbon nanotubes was investigated. Four independent variables including pH, CNTs dosage, contact time, and agitation speed were carried out to determine the influence of these parameters on the adsorption capacity of the lead from water. The morphology of the synthesized multiwall carbon nanotubes (MWCNTs) was characterized by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) in order to measure the diameter and the length of the CNTs. The diameters of the carbon nanotubes were varied from 20 to 40 nm with average diameter at 24 nm and 10 micrometer in length. Results of the study showed that 100% of lead was removed by using COOH-MCNTs at pH 7, 150 rpm, and 2 hours. These high removal efficiencies were likely attributed to the strong affinity of lead to the physical and chemical properties of the CNTs. The adsorption isotherms plots were well fitted with experimental data.
231 citations
TL;DR: In this article, the authors predict the currentvoltage (I−V) characteristics and contact resistance of end-contacted metal electrodes−graphene and metal electrode−carbon nanotube (CNT) interfaces for five metals, Ti, Pd, Pt, Cu, and Au, based on the first-principles quantum mechanical (QM) density functional and matrix Green's function methods.
Abstract: In this paper, we predict the current−voltage (I−V) characteristics and contact resistance of “end-contacted” metal electrode−graphene and metal electrode−carbon nanotube (CNT) interfaces for five metals, Ti, Pd, Pt, Cu, and Au, based on the first-principles quantum mechanical (QM) density functional and matrix Green’s function methods. We find that the contact resistance (normalized to surface C atoms) is 107 kΩ for Ti, 142 kΩ for Pd, 149 kΩ for Pt, 253 kΩ for Cu, and 187 kΩ for Au. This can be compared with the contact resistance (per C) for “side-contacted” metal−graphene or metal−CNT interfaces of 8.6 MΩ for Pd, 34.7 MΩ for Pt, 630 MΩ for Cu, etc. Those are in good agreement with available experimental results, 40.5 MΩ for Pt, for example. Thus, compared to the values for side-contacted interfaces from QM, we find a decrease in contact resistance by factors ranging from 6751 for Au and 2488 for Cu, to 233 for Pt and 60 Pd, to 8.8 for Ti. This suggests a strong advantage for developing technology to ac...
195 citations