Improved heat management of electronic devices

“Remarkably, the presence of the few-layer graphene domains resulted in a reasonable degree of visible light transparency of the overall film”G. Deokar

Scientists at King Abdullah University of Science and Technology in Saudi Arabia have devised a quick and effective approach to fabricating an innovative carbon material able to dissipate heat in electronic devices. The approach, which is based on fabricating graphite sheets only 100 nanometers thick, could have potential applications in solar cells and gas sensors, as well as helping the next generation of smartphones to maintain a low temperature.

The formidable amount of microelectronics inside our smartphones has to be kept cool, which is a major problem currently being tackled by research. While numerous electronic devices use high-quality micrometer-thick graphite films to dissipate the heat generated by electronic components, producing these graphite films often uses polymer as a source material in a difficult and energy-intensive process. This approach is also unable to make films thinner than a few micrometers, and require a multi-stage process with temperatures up to 3200⁰C.

In this new study, however, nanometer-thick graphite films (NGFs) were grown on nickel foils using chemical vapor deposition (CVD), where the nickel catalytically converts hot methane gas into graphite on its surface. As described in Nanotechnology [Deokar et al. Nanotechnology (2020) DOI: 10.1088/1361-6528/aba712], NGFs were produced with a CVD growth step that took only five minutes at a reaction temperature of 900⁰C.

The NGFs can be grown in sheets of up to 55 square centimeters, and on both sides of the foil, which can then be extracted and transferred to other surfaces without the polymer supporting layer commonly needed for handling single-layer graphene films. The NGFs could complement or provide an alternative to films currently produced from natural graphite flakes or polymer sheets.

In addition to heat dissipation, the process achieved some sections of the NGF that were only a few carbon sheets thick. As lead author G. Deokar said "Remarkably, the presence of the few-layer graphene domains resulted in a reasonable degree of visible light transparency of the overall film”.

Using an electron microscope, cross-sectional transmission electron microscopy (TEM) images of the NGF on nickel were captured. The variable number of graphene layers was shown to correlate with the orientation, size and boundaries of the nickel grains at the surface of the polycrystalline metal foil.

These NGFs could find uses for heat management in the new flexible phones being produced, as integration would be less expensive and more robust than graphene film. Such conducting, semi-transparent NGFs could also find uses as components of solar cells, or sensor materials for detecting NO2 gas, and the researchers now hope to integrate NGFs into devices to act as a multifunctional active material.