Researchers bind hydrogen to graphene in a super-fast reaction that also opens up a bandgap

Researchers from Göttingen and Pasadena (USA) have produced an "atomic scale movie" showing how hydrogen atoms chemically bind to graphene in one of the fastest reactions ever studied. The team found that by adhering hydrogen atoms to graphene, a bandgap can be formed.

Hydrogen binds to graphene in 10 femtoseconds imageThe hydrogen atom (blue) hits the graphene surface (black) and forms a bond with a carbon atom (red). The high energy of the hydrogen atom is first absorbed by neighboring carbon atoms (orange and yellow) and then passed on to the graphene as a sound wave

The research team bombarded graphene with hydrogen atoms. "The hydrogen atom behaved quite differently than we expected," says Alec Wodtke, head of the Department of Dynamics at Surfaces at the Max Planck Institute (MPI) for Biophysical Chemistry and professor at the Institute of Physical Chemistry at the University of Göttingen. "Instead of immediately flying away, the hydrogen atoms 'stick' briefly to the carbon atoms and then bounce off the surface. They form a transient chemical bond," Wodtke exclaims. Something else also surprised the scientists: The hydrogen atoms have a lot of energy before they hit the graphene, but not much left when they fly away. It seems that hydrogen atoms lose most of their energy on collision, but where it goes remained to be examined.

Canada-based University of Guelph to receive grant for graphene research

A professor at the University of Guelph in Canada is receiving $1.4 million CAD (a little over $1 million USD) over the next seven years toward his research, which includes developing practical graphene applications. Prof. Aichen Chen was recently named as a tier-1 Canada Research Chair in electrochemistry and nanoscience, a title that came with the $1.4 million in funding.

For the past five years, Chen has been working with graphene — aiming to use it to create innovative green technologies for projects like energy storage and clean drinking water.

Researchers manipulate the width of GNRs to create quantum chains that could be used for nano-transistors and quantum computing

Researchers at EMPA (Swiss Federal Laboratories for Materials Science and Technology), along with colleagues from the Max Planck Institute for Polymer Research in Mainz and other partners, have succeeded in precisely controlling the properties of graphene nano-ribbons (GNRs) by specifically varying their shape. This can be used to generate specific local quantum states, and could in the future be used for precise nano-transistors or possibly even quantum computing.

Researchers manipulate the width of GNRs to create quantum chains that could be used for nano-transistors and quantum computing image

The team has shown that if the width of a narrow graphene nano-ribbon changes, in this case from seven to nine atoms, a special zone is created at the transition: because the electronic properties of the two areas differ in a special, topological way, a "protected" and thus very robust new quantum state is created in the transition zone. This local electronic quantum state can be used as a basic component to produce tailor-made semiconductors, metals or insulators - and perhaps even as a component in quantum computers.

Puzzling results explained: a multiband approach to Coulomb drag and indirect excitons in dual-layer graphene

A theoretical collaborative study by the University of Antwerp (Belgium), the University of Camerino (Italy) and the University of New South Wales (Australia) has explained previously mystifying experimental results obtained independently by two research groups in the USA, which showed coupled holes and electrons in dual-layer graphene structures sometimes moved in exactly the opposite direction to that predicted.

A multiband approach to Coulomb drag and indirect excitons in dual-layer graphene imageDevice schematic: one sheet of conductive bilayer graphene carries electrons, the other, separated by insulating hBN, carries holes

The new work showed that this apparently contradictory phenomenon is associated with the bandgap in dual-layer graphene structures, a bandgap which is very much smaller than in conventional semiconductors.

International team produces nano-transistors from carefully controlled GNRs

An international team of researchers from Empa, the Max Planck Institute for Polymer Research in Mainz and the University of California at Berkeley has succeeded in growing graphene ribbons exactly nine atoms wide with a regular armchair edge from precursor molecules. The specially prepared molecules are evaporated in an ultra-high vacuum for this purpose. After several process steps, they are put on a gold base to form the desired nanoribbons of about one nanometer in width and up to 50 nanometers in length.

Researchers create GNR-based transistors image

These structures have a relatively large and, most importantly, precisely defined energy gap. This enabled the researchers to go one step further and integrate the graphene ribbons into nanotransistors. Initially, however, the first attempts were not so successful: Measurements showed that the difference in the current flow between the "ON" state (i.e. with applied voltage) and the "OFF" state (without applied voltage) was far too small. The problem was the dielectric layer of silicon oxide, which connects the semiconducting layers to the electrical switch contact. In order to have the desired properties, it needed to be 50 nanometers thick, which in turn influenced the behavior of the electrons.