Graphene Gets a Tunable Band Gap

Schematic displaying the HyTII process depicting nitrogen (N+) incident with a graphene-on-copper (Cu) sample.

Schematic displaying the HyTII process depicting nitrogen (N+) incident with a graphene-on-copper (Cu) sample.

Graphene is an incredible material for many applications, but it is limited by the fact that it lacks a band gap. To solve this, researchers have tried nitrogen doping to add a usable transport gap. Unfortunately, this usually results in films that have defects, low stability, or aren’t uniform, which defeats the purpose of using graphene in the first place. Now scientists at the US Naval Research Laboratory (NRL) have developed a new technique for nitrogen doping that gives graphene a stable, tunable band gap.

Since the discovery that a single atomic layer of sp2 bonded carbon atoms, termed graphene, could be isolated from bulk graphite, a plethora of remarkable electronic and spintronic properties have emerged. However, few applications are forthcoming because graphene lacks a bandgap and its doping is difficult to control, rendering graphene devices competitive only for highly-specialized device technologies.

Dr. Cory Cress, materials research engineer, NRL

The NRL researchers used a technique called hyperthermal ion implantation (HyTII). With this method, they were able to precisely control the concentration of nitrogen and the depth where it is placed on the graphene lattice. This accuracy reduces defects and improves the material’s stability. The resulting films have high-quality electronic transport properties. Various aspects of the study are described in the journals ACS Nano and Physical Review B.

“Our measurements of these devices strongly indicate that we have finally fabricated a graphene film with a tunable bandgap, low defect density, and high stability,” said Dr. Adam L. Friedman, research physicist, NRL. “We therefore hypothesize that HyTII graphene films have great potential for electronic or spintronic applications for high-quality graphene where a transport or bandgap and high carrier concentration are desired.”

Source: NRL

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