All issues plaguing graphene research can go away now

Jan 24, 2015 08:34 GMT  ·  By

At 6100 Main Street, Houston, TX 77005, United States lies the headquarters of the William Marsh Rice University, commonly referred to as Rice University. It is there that some of the biggest issues of graphene have just been solved.

Graphene is a wonder material, made of monoatomic sheets of carbon arrayed in hexagonal, planar molecules.

The substance is believed to be the next big thing in more or less every layer of technology, from superconductors and semiconductors to displays, armor and super-tough ropes.

However, there is one problem that has been consistently preventing scientists from preserving the full durability of graphene: the layer edges always section off irregularly, cutting down the endurance significantly, along with every other mechanical property worth noting.

Theoretical physicists at Rice University have now come up with a way to fracture graphene nanoribbons in order to get the edges they need.

It's all about proper tailoring

According to the research team, it is possible to control the edge properties of graphene nanoribbons by careful application of force at the right temperature.

Perfect graphene looks like a wire grid of hexagons, with the edges of zigzags being all parallel lines (/////). Since the way atoms line up along the edge determines whether the graphene is metallic or semiconducting, controlling them is critical.

Hexagons turned at 30 degrees gives the edges flat tops and bottoms held together by the diagonals. So far, ribbon width has determined whether graphene sheets become metallic (current passes freely) or semiconducting (some control over the current is available).

The Rice team used a complicated computer modeling technique to show how to rip nanoribbons in order to end up with zigzag edges or reconstructed zigzags (where atoms are enticed to shift and form connected rings of five and seven atoms, not six). Reconstructed zigzags are the most stable, so they are preferred by manufacturers.

The new tailoring method

ZiAng Zhang, a Rice graduate student and the paper's lead author, worked with physicist Boris Yakobson and Rice postdoctoral researcher Alex Kutana to analyze the energy output of every atom and learn how thermodynamic and mechanical forces would accomplish the goal.

Their findings led them to a method that heats the graphene to 1,000 kelvins and applies a low but sustained force along one axis, thus cracking the material in such a manner that fully reconstructed 5-7 rings will form. Using low heat and high force leads to better zigzags in contrast.