493 research outputs found
Sub 20 nm Short Channel Carbon Nanotube Transistors
Carbon nanotube field-effect transistors with sub 20 nm long channels and
on/off current ratios of > 1000000 are demonstrated. Individual single-walled
carbon nanotubes with diameters ranging from 0.7 nm to 1.1 nm grown from
structured catalytic islands using chemical vapor deposition at 700 degree
Celsius form the channels. Electron beam lithography and a combination of HSQ,
calix[6]arene and PMMA e-beam resists were used to structure the short channels
and source and drain regions. The nanotube transistors display on-currents in
excess of 15 microA for drain-source biases of only 0.4 Volt.Comment: Nano Letters in pres
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Growth of high-density carbon nanotube forests on conductive TiSiN supports
This is the accepted manuscript. The final version is available at http://scitation.aip.org/content/aip/journal/apl/106/8/10.1063/1.4913762.We grow vertically aligned carbon nanotube forests on refractory conductive films of TiSiN and achieve area densities of (5.1 ± 0.1) × 1012 tubes cm−2 and mass densities of about 0.3 g cm−3. The TiSiN films act as diffusion barriers limiting catalyst diffusion into the bulk of the support, and their low surface energy favours catalyst de-wetting, inducing forests to grow by the root growth mechanism. The nanotube area density is maximised by an additional discontinuous AlOx layer, which inhibits catalyst nanoparticle sintering by lateral surface diffusion. The forests and the TiSiN support show ohmic conduction. These results suggest that TiSiN is the favoured substrate for nanotube forest growth on conductors and liable of finding real applications in microelectronics.The authors acknowledge funding from European project Grafol. J.Y. thanks Sarah Fearn and David McPhail from Imperial College London for use of the SIMS instrument. A.W.R. is supported by EPSRC (Platform Grant Nos. EP/F048009/1 and EP/K032518/1) and Korean Institute for Energy Research. H.S. acknowledges a research fellowship from the Japanese Society for the Promotion of Science
Bias Dependence and Electrical Breakdown of Small Diameter Single-Walled Carbon Nanotubes
The electronic breakdown and the bias dependence of the conductance have been
investigated for a large number of catalytic chemical vapor deposition (CCVD)
grown single-walled carbon nanotubes (SWCNTs) with very small diameters. The
convenient fabrication of thousands of properly contacted SWCNTs was possible
by growth on electrode structures and subsequent electroless palladium
deposition. Almost all of the measured SWCNTs showed at least weak gate
dependence at room temperature. Large differences in the conductance and
breakdown behavior have been found for "normal" semiconducting SWCNTs and small
band-gap semiconducting (SGS) SWCNTs.Comment: submitted to Journal of Applied Physic
Nanoelectromechanical Sensors based on Suspended 2D Materials
The unique properties and atomic thickness of two-dimensional (2D) materials
enable smaller and better nanoelectromechanical sensors with novel
functionalities. During the last decade, many studies have successfully shown
the feasibility of using suspended membranes of 2D materials in pressure
sensors, microphones, accelerometers, and mass and gas sensors. In this review,
we explain the different sensing concepts and give an overview of the relevant
material properties, fabrication routes, and device operation principles.
Finally, we discuss sensor readout and integration methods and provide
comparisons against the state of the art to show both the challenges and
promises of 2D material-based nanoelectromechanical sensing.Comment: Review pape
Non-Volatile Resistive Switching of Polymer Residues in 2D Material Memristors
Two-dimensional (2D) materials are popular candidates for emerging nanoscale
devices, including memristors. Resistive switching (RS) in such 2D material
memristors has been attributed to the formation and dissolution of conductive
filaments created by the diffusion of metal ions between the electrodes.
However, the area-scalable fabrication of patterned devices involves polymers
that are difficult to remove from the 2D material interfaces without damage.
Remaining polymer residues are often overlooked when interpreting the RS
characteristics of 2D material memristors. Here, we demonstrate that the
parasitic residues themselves can be the origin of RS. We emphasize the
necessity to fabricate appropriate reference structures and employ atomic-scale
material characterization techniques to properly evaluate the potential of 2D
materials as the switching layer in vertical memristors. Our
polymer-residue-based memristors exhibit RS typical for a filamentary mechanism
with metal ion migration, and their performance parameters are strikingly
similar to commonly reported 2D material memristors. This reveals that the
exclusive consideration of electrical data without a thorough verification of
material interfaces can easily lead to misinterpretations about the potential
of 2D materials for memristor applications.Comment: 30 page
Purification of Nanoparticles by Size and Shape
Producing monodisperse nanoparticles is essential to ensure consistency in biological experiments and to enable a smooth translation into the clinic. Purification of samples into discrete sizes and shapes may not only improve sample quality, but also provide us with the tools to understand which physical properties of nanoparticles are beneficial for a drug delivery vector. In this study, using polymersomes as a model system, we explore four techniques for purifying pre-formed nanoparticles into discrete fractions based on their size, shape or density. We show that these techniques can successfully separate polymersomes into monodisperse fractions
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