Cooling the powerful electronics in the latest smartphones can be a major challenge. Researchers at King Abdullah University of Science and Technology have developed a fast and efficient method for creating carbon materials ideal for dissipating heat from electronic devices. This versatile material can find other applications, from gas sensors to solar panels.
Many electronic devices use graphite films to conduct and dissipate the heat generated by electronic components. Although graphite is a natural form of carbon, thermal management in electronics is a demanding application and often depends on the use of high-quality micron-thick graphite films. “However, the method of making these graphite films using polymers as raw materials is complex and energy-intensive,” explains Gitanjali Deokar, a postdoc in Pedro Costa’s lab who led the work. The films are made through a multi-step process that requires temperatures up to 3,200 degrees Celsius and cannot produce films thinner than a few microns.
Deokar, Costa and their colleagues have developed a fast and energy-efficient method for making graphite sheets about 100 nanometers thick. The team used a technique called chemical vapor deposition (CVD) to grow nanometer-thick graphite films (NGFs) on nickel foil, where the nickel catalyzes the conversion of hot methane into graphite on its surface. “We achieved NGF in just a 5-minute CVD growth step at a reaction temperature of 900 degrees Celsius,” Deokar said.
NGF can grow into sheets up to 55 cm2 in area and grow on both sides of the foil. It can be removed and transferred to other surfaces without the need for a polymer support layer, which is a common requirement when working with single-layer graphene films.
Working with electron microscopy expert Alessandro Genovese, the team obtained transmission electron microscopy (TEM) images of cross-sections of NGF on nickel. “Observing the interface between graphite films and nickel foil is an unprecedented achievement and will provide additional insights into the growth mechanism of these films,” Costa said.
The thickness of NGF falls between commercially available micron-thick graphite films and single-layer graphene. “NGF complements graphene and industrial graphite sheets, adding to the arsenal of layered carbon films,” Costa said. For example, due to its flexibility, NGF can be used for thermal management in flexible mobile phones that are now starting to appear on the market. “Compared with graphene films, the integration of NGF will be cheaper and more stable,” he added.
However, NGF has many uses beyond heat dissipation. An interesting feature highlighted in the TEM images is that some parts of the NGF are only a few layers of carbon thick. “Remarkably, the presence of multiple layers of graphene domains ensures a sufficient degree of visible light transparency throughout the film,” Deoka said. The research team hypothesized that the conductive, translucent NGF could be used as a component of solar cells or as a sensing material for detecting nitrogen dioxide gas. “We plan to integrate NGF into devices so that it can act as a multifunctional active material,” Costa said.
Further information: Gitanjali Deokar et al., Rapid growth of nanometer-thick graphite films on wafer-scale nickel foil and their structural analysis, Nanotechnology (2020). DOI: 10.1088/1361-6528/aba712
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Post time: Sep-05-2024