Technical / Research - Page 3

Researchers from Cambridge (UK) and CNRS (France) have developed an ultra-fast mode-locked laser using Graphene. Graphene based lasers can be easier and cheaper to make than semiconductor saturable absorber mirrors (SESAMs) based lasers, and will be less limited in their bandwidth.

Graphene ultra-fast laser

The team studied how light is absorbed in graphene and how photo-excited charge carriers behave in the material. In particular, they highlighted the key role of "Pauli blocking" in saturating the light absorption. Because of the Pauli exclusion principle, when pumping of electrons in the excited state is quicker than the rate at which they relax, the absorption saturates. This is because no more electrons can be excited until there is "space" available for them in the excited state.

Since the Dirac electrons in graphene linearly disperse, this means that it is the most wideband saturable light absorber ever, far out-passing the bandwidth provided by any other known material.

The team is now in the process of optimizing a fully functioning wideband tunable laser based on graphene, as well as trying similar experiments with graphene oxide.

Via optics.org

A new research in the National Institute of Standards and Technology (NIST) and the university of Pennsylvania is working towards a Graphene based structure that can be promising for capturing hydrogen. Graphene is not really suited to store hydrogen, but if you stack oxidized Graphene sheets (in a Graphene-Oxide-Framework, or GOF) than it can hold hydrogen in higher quantities. The team says that GOFs can store at least a hundred times more hydrogen than ordinary Graphene Oxide. This can potentially be very useful for fuel-cells or other applications.

Via AZoNano

Scientists from the Leibniz Institute for Solid State and Materials Research say they have developed a very simple and cheap procedure for making Graphene - growing it on the surface of commercially available silicon carbide wafers.

Victor Aristov and his team successfully synthesized graphene on commercially available cubic SiC/Si substrates of less than 300mm in diameter - something that's never been done before.

The result is graphene flakes electronically decoupled from the substrate - crucial to preserve Graphene's almost magical properties.

Via TGDaily

RIBER announced today that it has sold a Compact 21 system to the Innovation of High Performance Microelectronics (IHP) laboratory in Germany.

The system sold to IHP will thus be equipped with a gas injector and be devoted to the development of graphene-based applications. Compact 21 is the MBE research system that has sold the most units in the world. It is highly flexible and offers great  adaptability to meet the most demanding specifications of applied research on compound semi-conductor materials.

Source

Researchers at Stanford University have successfully developed a brand new concept of OLEDs with a few nanometer of graphene as transparent conductor. This paved the way for inexpensive mass production of OLEDs on large-area low-cost flexible plastic substrate, which could be rolled up like wallpaper and virtually applied to anywhere you want. The researchers say that Graphene has the potential to be transparent, high-performance, highly conductive and cheaper by several orders of magnitude than current ITO based solutions.

Traditionally, indium tin oxide (ITO) is used in OLEDs, but indium is rare, expensive and difficult to recycle. Scientists have been actively searching for an alternative candidate.

The next generation of optoelectronic devices requires transparent conductive electrodes to be lightweight, flexible, cheap, environmental attractive, and compatible with large-scale manufacturing methods. Graphene (a single layer of graphite) is becoming a very promising candidate due to its unique electrical and optical properties. Very recently, Junbo Wu et al., researchers at Stanford University, successfully demonstrated the application of graphene in OLEDs for the first time.

Junbo Wu, leading researcher of the development, said that they achieved OLEDs on graphene with performance similar to a control device on conventional ITO transparent anodes, which is very exciting and promising for real-world applications. Because Graphene is only a couple of nanometers thick, it can give device designers more freedom.

For detailed information on this research, please refer to http://pubs.acs.org/doi/abs/10.1021/nn900728d.

Via OLED-Info

Researchers from UCLA has created a new Graphene nanostructure called Graphene nanomesh (GNM). The new structure is able to open up a band gap in a large sheet of graphene to create a highly uniform, continuous semiconducting thin film that may be processed using standard planar semiconductor processing methods.

The nanomesh can have variable periodicities, defined as the distance between the centers of two neighboring nanoholes. Neck widths, the shortest distance between the edges of two neighboring holes, can be as low as 5 nanometers. This ability to control nanomesh periodicity and neck width is very important for controlling electronic properties because charge transport properties are highly dependent on the width and the number of critical current pathways.

Via AzoNano

Researchers at Georgia Tech say they have developed a one step process that enables both n- and p-type doping of large area graphene surfaces. The used commercially available spin on glass (SOG) material and applied to a sheet of graphene and then exposing it to electron beam radiation. To create both doping types you simply vary the exposure time, with higher levels of energy producing p-type areas.

Via NewElectronics