April 2011

Researchers from the Naval Research Laboratory (NRL) shown that the valley degree of freedom in graphene can be polarized through scattering off a line defect. This makes valley-based electronics (valleytronics) one step closer to reality. Valleytronics may present a middle-ground between spintronics and electronics using the valley degree of freedom (which exists in certain crystals, including graphene).

The NRL research shows that an extended line defect in graphene acts as a natural valley filter. "As the structure is already available, we are hopeful that valley-polarized currents could be generated in the near future" said Dr. Daniel Gunlycke who made the discovery together with Dr. Carter White. Both work in NRL's Chemistry Division.

Researchers from the National Institute of Standards and Technology (NIST) have shown that the electronic properties of two layers of graphene vary on the nanometer scale - not only in the strength of the electric charges between the two layers but they also actually reverse in sign to create randomly distributed puddles of alternating positive and negative charges.

This means that bi-layer graphene (two stacked graphene sheets) acts more like a semiconductor that a single sheet. A band gap may also form on its own due to variations in the sheets' electrical potential caused by interactions among the graphene electrons or with the substrate.

Researhcers from the University of Technology in Sydney, Australia, developed a new material called Graphene paper (GP), made from Graphite which is lighter, stronger, harder and more flexible than steel. It's also eco-friendly and recyclable. The new material is thinner than paper and ten times stronger than steel. The researchers say that the new material can be used in the automotive and aviation industries - to create lighter planes and cars which will be require less fuel, and yet be even more safe.

The new GP is made using raw graphite which is milled and purified using a chemical bath. This allows it to be pressed into thin sheets.

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.

Researchers from MIT are developing graphene based membranes for gas separation. They expect those membranes to have very high permeance which would lead into high energy efficiency. The membranes will also have a high degree of selectivity through size exclusion. The research will focus on separating methane from hydrogen at first - which is useful for natural gas processing.

This research was just granted some seed money and will last for 2 years.

Researchers from the University of Arizona and Rensselaer Polytechnic Institute used Graphene to reinforce ceramic composites - and make it more fracture resistant. The team says they have significantly increased the toughness of a ceramic and made the first observations of graphene that arrest crack propagation and force the crack to change directions in not just two but also three dimensions.

Researchers from the University of Maryland (UMD) discovered that missing atoms in Graphene (called vacancies) act as tiny magnets (they have a magnetic moment) - and interact strongly with the electrons in graphene which carry electrical currents, giving rise to a significant extra electrical resistance at low temperature, known as the Kondo effect.

The researchers say that if you arrange the vacancies in the right order, you could get ferromagnetism. This could lead the way to nanoscale sensors of magnetic fields and could be useful in spintronics, too.

Aixtron sold a 300mm Black Magic Graphene deposition system to the National Institute of Advanced Industrial Science and Technology (AIST) in Japan. The order was placed in the beginning of 2011 and will be delivered in 3Q 2011. It will be installed in the AIST Super Clean Room at Tsukuba and commissioned by the local Aixtron support team. The system will be used for the development and application of Nanocarbon materials.

Researchers from IBM developed a graphene transistor with a record cut-off frequency of 155 Ghz and the shortest gate length ever (just 40nm). They used a diamond-like carbon as the top layer of the substrate on which the Graphene is deposited. This material is a great substrate for Graphene. It's a non-polar dielectric material - so it does not 'trap' or scatter charges, doesn't absorb a lot of water and has excellent thermal conductivity. It's also cheap to make and widely used today in the semiconductor industry.

Just over a year ago, IBM developed a 100Ghz RF graphene transistor - so the recent development is a 50% improvement over the previous design.

Researchers from the University of Illinois discovered that graphene transistors have a nanoscale cooling effect that reduces their temperature. Using an atomic force microsope the team made the first ever nanometer-scale temperature measurements of a graphene transistor. This revealed that thermoelectric cooling effects can be stronger at graphene contacts than resistive heating, actually lowering the temperature of the transistor.

This means that graphene-based electronics could require very little cooling (or none at all).