GNRs - Page 10

Researchers from the Rensselaer Polytechnic Institute have discovered new graphene based materials that can be customized to produce specific band gap and magnetic properties (i.e. have tunable functionality in electronics). The materials may be used to enable new nanoelectronics, optics, and spintronics devices.

The researchers found out that graphitic nanoribbons can be segmented into several different surface structures called nanowiggles. Each of these structures produces highly different magnetic and conductive properties. This means that you can basically create a new graphene nanostructure that is customized for a specific task or device.

Researchers from China's Fudan University say that graphene nanoribbons could potentially be used to create spin valves (one of the basic building blocks of spintronics). They present a theoretic spin valve design that uses two hexagonal graphene "nanoislands" with zig-zag edges, which serve as the magnetic layers in the spin valve, connected by an armchair-type nanoribbon as the non-magnetic layer, through which the electrons can pass depending on the relative alignment of the spins in the nanoislands.

They calcualte that this design enables stable spin configurations at certain energies, and there will be stable configurations in which the islands are polarized either parallel or antiparallel with respect to each other — a necessary requirement for a spin valve.

The National Science Foundation (NSF) and the National Research Initiative (NRI) awarded $1.4 million to Cornell University for a four years electronic device-scaling project utilizing graphene nanoribbons. Part of the grant will be used toward developing a website for Women in Nanoelectronics, a national organization designed to attract young women to nanoscience disciplines.

Researchers from Rice University and the Hong Kong Polytechnic University discovered that Graphene nanoribbons could stand tall on substrates and also form arcs. The contact between the graphene and substrate (which could be diamond and also nickel) is very light and so the graphene retains nearly all of its inherent electrical or magnetic properties. Using such a design can theoretically enable putting 100 trillion graphene-wall field-effect transistors (FETs) on a square-centimeter chip.

According to James Meindl (from the Georgia Institute of Technology) graphene will only become a viable alternative once CMOS semiconductor manufacturing will reach 7 nanometer - which will happen around 2024 (according to Moore's law).

Meindl believes that the most likely usages of graphene is switches - and he's working on 15 nanometer-wide ribbons that could rival silicon.

Researchers from the UK and Sweden have investigated how graphene nanoribbons grow from an anthracene polymer on a gold substrate, using simluations on a supercomputer. They discovered that in the most likely nanoribbon growth process, the gold substrate acts as more than just a support where the reaction can take place. The gold actually catalyzes the reaction.

It turns out that the graphene nanoribbons grow in a way that resembles the domino effect.

Researchers from Berkeley built a microscale device that responds to light at terahertz frequencies. The device is an array made of graphene microribbons. By varying the width of the ribbons and the concentration of charge carriers in them, the scienstists were able to control the collective oscillations of electrons (plasmons) in the microribbons.

Scientists from The University of Nottingham, UK, developed a new self-assembly based method to create sulphur-terminated graphene nanoribbon within a single-walled carbon nanotube. The team have demonstrated that carbon nanotubes can be used as nanoscale chemical reactors and chemical reactions involving carbon and sulphur atoms held within a nanotube lead to the formation of atomically thin strips of carbon, known as graphene nanoribbon, decorated with sulphur atoms around the edge.

These ribbons have some interesting physical properties and they are suitable for applications in electronic and spintronics devices - more so than 'regular' graphene.

Researchers from the Beijing National Laboratory for Condensed Matter Physics and Peking University in China developed a simple and scalable method for manufacturing graphene nanoribbons. The idea is to cover a sheet of graphene with 1 µm polysterene spheres, which self-assembled on the surface into tightly packed arrays, and then etching with oxygen plasma.

The etching process patterned the graphene into complex shapes including dumbbells (see photo above), ribbons, chains and polygonal rings. Using different etching time and sphere packing order you can control which shape you'll get. When you wash away the spheres, you can recover the sheet in the shape you created. The narrow ribbons exhibit a bandgap, as opposed to large graphene sheets, and this can make them useful for electronic components.