Electronics - Page 19

Researchers at the Korean IBS, in collaboration with Sungkyunkwan University, have designed a novel graphene-based stretchable and flexible memory device for wearable electronics.

The team has constructed a memory called two-terminal tunnelling random access memory (TRAM), where two electrodes, referred to as drain and source, resemble the two communicating neurons of the synapse in the brain. While mainstream mobile electronics use the so-called three-terminal flash memory, the advantage of two-terminal memories like TRAM is that two-terminal memories do not need a thick and rigid oxide layer. While Flash memory is more reliable and has better performance, TRAM is more flexible and can be scalable, according to the team.

A team of researchers at Nanyang Technological University, Singapore, has produced a stretchy micro-supercapacitor using ribbons of graphene. The team produces stretchable electrodes and integrated them into a supercapacitor, in what can be seen as a promising step towards bendy power sources for flexible electronics.

In this study, the team focused on the fact that graphene can be flexible and foldable, but it cannot usually be stretched; They attempted to fix that problem by looking at skin, which has a wave-like microstructure, and started to think of how to make graphene also more like a wave. They started by making graphene nano-ribbons, having more control over its structure and thickness that way (which can affect the conductivity of the electrodes and how much energy the supercapacitor overall can hold).

Researchers from Moscow Institute of Physics and Technology (MIPT), in collaboration with researchers from other Russian institutions, have designed a way to acquire 2D graphene-like layers of various rock salts. Thanks to the unique properties of atomically thin materials, this opens up fascinating prospects for nanoelectronics. Based on the computer simulation, they derived the equation for the number of layers in a crystal that will produce ultrathin films with potential applications in nanoelectronics.

Previous theoretical studies suggested that under certain conditions, films with a cubic structure and ionic bonding could spontaneously convert to a layered hexagonal graphitic structure in what is known as graphitisation. However, there was very little experimental data to make any practical use of this proposal.

A team of researchers from China and Japan has designed a new method to make minuscule ribbons of graphene that are highly sought-after building blocks for semiconductor devices thanks to their predicted electronic properties. These structures, however, have proven challenging to make.

Previous attempts at making graphene nanoribbons relied on placing sheets of graphene over a layer of silica and using atomic hydrogen to etch strips with zigzag edges, a process known as anisotropic etching. This method, however, only worked well to make ribbons that had two or more graphene layers. Irregularities in silica created by electronic peaks and valleys roughen its surface, so creating precise zigzag edges on graphene monolayers was a challenge.

Researchers at Rice University have created rivet graphene, 2D carbon that incorporates carbon nanotubes for strength and carbon spheres that encase iron nanoparticles, which enhance both the material’s portability and its electronic properties.

Transferring graphene grown via CVD is usually done with a polymer layer to keep it from wrinkling or ripping, but the polymer tends to leave contaminants behind and degrade graphene’s abilities to carry a current. According to the Rice team, rivet graphene proved tough enough to eliminate the intermediate polymer step, and the rivets also make interfacing with electrodes far better compared with normal graphene’s interface, since the junctions are more electrically efficient. Finally, the nanotubes give the graphene an overall higher conductivity. So for using graphene in electronic devices, this is said to be an all-around superior material.

Researchers in the Amber materials science research center at Trinity College Dublin, Ireland, have discovered a new behavior of graphene. They found that they can cause graphene to spontaneously assemble into ribbons and other shapes while lying on a surface. This could prove enough to make large graphene structures almost visible to the naked eye, and it operates in air at room temperature. The discovery was made almost accidentally while cutting graphene sheets, then realizing the techniques caused the graphene to spontaneously arrange itself.

In the short term, the researchers see their findings as potentially useful to pattern graphene sheets to simplify the production of electronic and other devices in larger volumes. However, they also think the self-assembly effect itself may be important as an active component of future sensors, actuators and machines.

Researchers from EPFL have reported the design of a tunable, graphene-based device that could significantly increase the speed and efficiency of wireless communication systems. Their system works at very high frequencies and is said to be delivering unprecedented results.

Current portable wireless systems usually come equipped with reconfigurable circuits that can adjust the antenna to transmit and receive data in the various frequency bands. Unfortunately, currently available technologies like MEMS and MOS that use silicon or metal do not work well at high frequencies - where data can travel much faster. For this end, the EPFL researchers have come up with a tunable graphene-based solution that enables circuits to operate at both low and high frequencies with unprecedented efficiency.

Researchers at the Georgia Institute of Technology have developed an electron beam technique to allow for the complete destruction of electronic data. The electron-beam writing technique that induces the deposition of carbon on a graphene surface, referred to as "focused electron beam induced deposition", is a type of direct-write additive lithographic technique. With the method, by altering the energy levels, exposure time, and location of the e-beam the rate of carbon deposition changes, leading to the re-write and direct-write events occurring.

This method allows for nanoscale engineering of future graphene-based devices for information. This means that not only can data be re-written, the original functionality of the device can be changed and energy storage devices, sensors and nanoelectronics could be re-configured.

Researchers at Exeter used their GraphExeter material (compressed ferric chloride molecules between two sheets of graphene) to bring flexible electronics a step closer. GraphExeter allows for a new system that is a better conductor of electricity than graphene, and can be used to make large, flat and flexible lighting.

The main advantage is that the material is capable of high luminosity, reportedly beating comparable products by 50% greater brightness. One limitation with the current developments in flexible screens is that the brightness that can be achieved decreases as the screen becomes larger, but GraphExeter is said to overcome this.

Scientists at The University of Manchester, along with a team at Shandong University, have designed a graphene-based electrical nano-device that could substantially increase the energy efficiency of fossil fuel-powered cars.

The nano-device, known as a 'ballistic rectifier', can convert heat which would otherwise be wasted from the car exhaust and engine body into a usable electrical current. The recovered energy can then be used to power additional automotive features such as air conditioning and power steering, or be stored in the car battery.