Electronics - Page 34

The National Science Foundation (NSF) awarded a $360,000 three-year grant to three professors from the University of California, Riverside (UCR) to further study th thermal properties of graphene. The future goal of this study is to find new heat-removal approaches for electronic and optoelectronic devices.

This specific project will investigate the effect of rotation angle on the thermal conductivity of twisted bilayer graphene. The UCR team will study the possibility of suppressing the phonon coupling in twisted graphene layers, allowing for the transfer of extraordinary large heat fluxes. The phonons are quanta of crystal lattice vibrations that carry heat in graphene.

Researchers from Cornell University have shown that in bilayer graphene, defects can influence the conductivity. In fact, the bilayer graphene, when it is stacked and staggered, has ripples (called solitons) which act like electrical highways. The rest of the non-rippled bi-layer graphene is semiconducting.

Up until now it was predicted that bilayer graphene is uniformly semiconducting when stacked and staggered. The researchers say that ideally they'd like to get rid of those solitrons, or control their formation - to have one "electrical highway" but not so many. So controlling bilayer graphene solitrons may enable controlling graphene's electrical properties.

Researchers from the University of Vienna managed to assemble a new structure of high-quality metal silicides (nickel, cobalt and iron) coated with a graphene sheets. Using angle-resolved photoemission spectroscopy (ARPES), the researchers studied the electronic properties of this new material.

It was found that the graphene protects the silicides against oxidation, while barely interacting with the silicides themselves. The unique properties of the graphene are widely preserved. This means that this new composite material is a good way to incorporate graphene with existing metal silicide technology, which will hopefully enable the usage of graphene in applications such as semiconductor devices, spintronics, photovoltaics and thermoelectrics.

Researchers from Chalmers University of Technology in Sweden have demonstrated how graphene can dissipate heat in silicon based electronics. The researchers placed a graphene sheet on an electronic device hot-spots - which reduced the working temperature by 25%.

All electronic devices generate heat. The devices (processors, for example) include those hot-spots where the work is most intensive. These spots are small (on a micro or nano scale). In their experiment, the hotspots had a normal temperature of 55 to 115 degrees Celsius. The graphene layer reduced it by up to 13 degrees.

Cambridge University's Graphene Centre (CGC) and Plastic Logic have signed a research collaboration agreement on graphene in flexible plastic electronics. Plastic Logic donated large scale deposition equipment to the CGC to support graphene development.

A flexible tiled 42" OTFT e-paper display, made by Plastic Logic

The co-research currently has three main activities:

• To develop graphene as a transparent, highly conductive layer for plastic backplanes for unbreakable LCD and flexible OLED displays.
• To develop new transistor structures that use graphene-like materials as the active layer.
• To explot the commercialization of graphene for flexible electronics.

The CGC was established in early 2013 with a £12 million grant from the UK government.

MIT researchers developed a new system, based on ferroelectric materials and graphene, that uses plasmons wave control to interconnect between electronic devices and light wave devices (such as fiber optics and photonic chips). Current such interconnectors are relatively slow and are often a bottleneck in those systems.

The new hybrid-material device can control surface plasmons wave (oscillations of electrons confined at interfaces between materials). The waves operate at terahertz frequencies in this new device, which is considered ideal for next-gen computing devices.

Researchers from the University of Copenhagen and the Chinese Academy of Sciences developed a transparent transistor made from just one molecular monolayer graphene. The graphene was used as transparent top-contacts in this design. The new "molecular computer chip" is built from three layers: gold, molecular components and graphene. The molecular transistor is switched on and of using a light impulse.

While such chips may be used to make integrated circuits in the future, the first application the researchers found was testing of molecular electronics. The new chip enables molecular placement with great precision, which speeds up molecular research.

Researchers from the Politecnico di Milano and the University of Illinois developed a Gigahertz graphene ring oscillator (1.28 GHz). They say that this oscillator appears to be less sensitive to fluctuations in the supply voltage compared to both conventional silicon CMOS and oscillators made from CNTs. And the best carbon nanotube ring oscillator made to date operates at just 50 MHz.

The researchers say that graphene based amplifiers and mixers have already been demonstrated, and now their graphene based oscillators marks the final major analog electronics building block enabled by graphene.

XG Sciences, one of the few companies in the world that offer xGnPs (Graphene Nanoplatelets, short stacks of graphene sheets made through a proprietary manufacturing process), say they have over 600 customers - in the automotive, electronics, battery and aerospace industries. The most active companies are Asian electronics and battery makers.

The company says they generated $4 million in revenue in 2012. Not all of this are product sales (for example they have a license agreement with Cabot Corporation, signed in 2011) - but it's still impressive considering that Lux Research estimates that the entire graphene market was just $9 million in 2012.

Researchers from Aalto University in Finland and Utrecht University in the Netherlands managed to create single-atom contacts to connect gold and graphene nanoribbons. In their experiments, they showed how a single chemical bond can be used to make an electrical contact to a graphene nanoribbon.

Using atomic force microscopy (AFM) and scanning tunneling microscopy (STM), the researchers mapped the structure of the graphene nanoribbons and then used voltage pulses from the tip of the scanning tunnelling microscope to form single bonds to the graphene nanoribbons, at a precise, specific location. The electric pulse removed a single hydrogen atom from the end of a graphene nanoribbon and this initiates the bond formation.