GNRs - Page 9

Researchers from IBM are studying how plasmons lose their energy in graphene. It turns out that plasmons lose their energy very slowly in graphene, which is good for photonics and quantum optics applications (the longer the plasmons last, the better).

The IBM researchers are using graphene nanoribbons, dots and nanodisk arrays grown on all sorts of substrates (silicon wafers, diamond-like carbon and SiO2, to name just a few). The researchers are using a new technique (based on Fourier transform IR spectrometer) to measure exact plasmon damping mechanisms and rates. Their most important finding is that the graphene plasmons appear to interact strongly with the vibrations of the silicon dioxide substrate surface atoms on which the graphene is deposited. This leads to so-called energy-dependent hybrid plasmon-phonon modes that disperse and decay very differently compared with those modes where graphene is deposited on non-planar diamond-like substrates.

Scientists from Rice University developed new ribbons made from vanadium-oxide and graphene-oxide (using a simple hydrothermal process) that make for superior Li-Ion battery cathodes. Batteries that use these new cathodes exhibit high energy and power densities. The new cathodes use materials that are relatively abundant and cheap.

The researchers found out that prototype cathodes used with halfcells can charge and discharge in 20 seconds and retain more than 90% of the capacity after more than 1,000 cycles. Those prototype cathodes were made from 84% VO2 (that hold 204 milliamp hours of energy per gram).

Researchers from Japan's Advanced Institute of Science and Technology (JAIST) and the University of Southampton in the UK have developed a new way to fabricate ultra-fine graphene nanodevices using helium-ion microscopy. Usually this tool is used for sub-nanometer probing and high-resolution imaging, but this time they have used to it to selectively sputter graphene to create intricate nanoscale designs.

The researchers used their new technique to develop two devices: ultrathin suspended graphene nanoribbons for extremely sensitive gas molecular sensors and densely integrated graphene Quantum Dots for quantum information processing technologies.

AZ Electronic Materials have entered into a licensing and sponsored research agreements with William Marsh Rice University in the field of graphene nanoribbons (GNRs) for application to electronic and advanced optical devices. AZ will gain exclusive world-wide rights to several patent families invented by Dr. James Tour and his working group at Rice, covering preparation methods and application of GNRs.

This technology could potentially enable low-cost functionalize GNR production from commercially available carbon sources such as CNTs. The method developed at Rice is reductively open CNTs to provide high quality, highly conductive GNRs. This method also provides an easy way to chemically functionalize them at their edges, which leads to greatly enhanced stability of coating formulations without deteriorating the performance. This allows the GNRs to be formulated in solvents common to electronic device manufacturing processes, which can be coated on substrates by industry-known methods. AZ also licensed Dr. Tour's high-yield approaches to graphene oxide.

Researchers from the Georgia Institute of Technology managed to create an substantial electronic bandgap in graphene nanoribbons - by coating bi-layer graphene on silicon carbide nanometer-scale steps. This could lead the way towards graphene based electronics.

The 1.4-nanometer ribbons created a bandgap of about 0.5 electron-volts. The researchers do not yet understand why the bent graphene creates the bandgap.

Researchers from the Max Planck Society are researching how a graphene nanowire conducts electricity. They discovered that electrons are tunneling through the graphene wire - by means of a quantum mechanical process. The researchers used a scanning tunneling microscope to perform complicated measurements to determine how the conductance of the carbon strip depends on its length and the energy of the electrons.

The researchers say that those graphene wires (or nanoribbons) are interesting research objects, but aren't very useful for nanoelectronics applications. At least not yet. 

Nobel Prize-winner (together with Andre Geim) Professor and Kostya Novoselov Professor Volodya Falko from Lancaster University have released a graphene roadmap. The roadmap discusses the different possible applications for graphene and also the different ways to produce the material.

The authors says that the first key application is conductors for touch-screen displays (replacing ITO), where they expect can be commercialized within 3-5 years. They also see rollable e-paper displays soon - prototypes could appear in 2015. Come 2020, we can expect graphene-based devices such as photo-detectors, wireless communications and THz generators. Replacing silicon and delivering anti-cancer drugs are interesting applications too - but these will only be possible at around 2030.

Researchers from IBM and University of California Riverside managed to make the slimmest graphene nanoribbon (GNR) ever - just 10 nm in width. Making one is virtually impossible, and the team created a large number of GNRs in parallel. The researchers say that the arrays cover about 50% of the prototype device channel area, which means that integrated circuits based on GNRs with the required high current densities are now possible. The narrow GNRs have a bandgap of about 0.2 eV.

The process the researchers used consists of two main steps: a top-down e-beam lithography step and a bottom-up self-assembly step involving a block copolymer template comprising alternating lamellae of the polymers PS and PMMA.

Nokia filed a new patent for a graphene-based photo detector. The new detector uses graphene as a photo-collecting layer, and also uses a graphene nanoribbon that acts as a field effect transistor to amplify the current and transfer it to the control electronics. Stacking several such detectors on top of each other with color filters can be done to detect colors.

The big advantage of this graphene-based photo detector is graphene's transparency. The graphene sheet itself absorbs only 2.3% of the light (and does it very evenly across the whole light spectrum) and so should perform much better than CMOS in low light conditions. The graphene sensor will also be vastly thinner than current technologies, and potentially cheaper to produce (once graphene itself is available on the cheap).

Researchers at the University of Delaware suggest that graphene sheets with nanopores (tiny holes) could be used for ultrafast DNA sequencing based on tiny holes. The study which is based on computer simulation suggests that threading DNA though nanopores can be used to detect the presence of different DNA bases. This is done by a current of ions flowing vertically through the pore or an electronic current flowing transversely through the graphene.

Graphene is just one atom thick and so the nanopore has contact with only a single DNA base. The researchers suggest using nanoribbons of graphene to enable fast and low-cost (less than $1,000) DNA sequencing.