The multifunctional, multi-layered carbon material could be used to perfect heat management in electronic devices, say researchers from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia.
In addition to keeping powerful electronics cool, the material is also said to potentially be able to find additional uses in applications such as solar cells and gas sensors.
The Difficulties in Using Graphite Films
Many electronic devices use graphite (a naturally occurring form of carbon) films to address the dissipation of heat that’s generated by their electronic components. However, in its traditional use in electronics, graphite (despite its high quality) is only used in micrometre-thick manufactured sheets, due to the intricate demands that engineers encounter when trying to control electrical heat management in devices.
Indeed, the method that’s used to make graphite films of such thinness (which involves the use of a polymer as a source material) is very complex and energy-intensive, as Geetanjali Deokar, a postdoctoral researcher in the laboratory of Pedro Costa at KAUST, explains. The graphite films are made in a multi-step process that requires temperatures of up to 3,200 °C. And again, due to the engineering demands, they cannot be produced any thinner than a few micrometres.
A Quick and Energy-efficient New Process
Now, as described in the KAUST research paper (published in the journal Nature), Costa’s research team claims to have developed a quick and energy-efficient way to make graphene sheets that are approximately 100 nanometres in thickness.
A diagram by KAUST researchers that reflects their polymer-free wet chemical transfer process for nanometre-thick graphene films grown on nickel foil. Image Credit: Xavier Pita, KAUST.
The researchers grew nanometre-thick graphene films (NGFs) on nickel foils through the use of chemical vapour deposition (CVD) in which the nickel converts hot methane gas into graphene on its surface. “We achieved NGFs with a CVD growth step of just five minutes at a reaction temperature of 900°C,” Deokar said in a statement.
The researchers found that the NGFs grew on both sides of the nickel foil, and those NGFs could be extracted and transferred to other surfaces without the need for a polymer supporting layer (which is, again, a common requirement when handling single-layer graphene films). In terms of how thick it is, the KAUST team’s NGFs sit somewhere between commercially available micrometre-thick graphite films and single-layer graphene.
Working with an electron microscopy specialist, the KAUST team also captured cross-sectional transmission electron microscopy images of the NGF on nickel, enabling the researchers to observe the interface of the graphite films to the nickel surface. The researchers call this an “unprecedented achievement that will shed additional light on the growth mechanisms of these films”.
The Implications of KAUST’s Achievement
Due to its flexibility, the KAUST team’s NGFs could be used in heat management in consumer-grade flexible smartphones. “NGF integration would be cheaper and more robust than what could be obtained with a graphene film,” said Costa.
Other potential applications, according to the KAUST team, involve the engineering of components in solar cells and sensor applications. “We plan to integrate NFGs in devices where they would act as a multifunctional active material,” Costa concluded.