Discovery of New Thermal Conductivity Properties in the Promising Carbon Material "Graphene"

Anritsu Corporation (President: Hirokazu Hamada) has discovered that nanoscale mesh-structured graphene exhibits thermal conductivity properties at room temperature that differ from conventional understanding. This discovery was made by Anritsu's Advanced Technology Research Laboratory, and a paper summarizing these research results has been published in the international scientific journal "2D Materials."

https://doi.org/10.1088/2053-1583/ae525a

While smartphones, 5G equipment, and personal computers continue to become smaller and higher-performing, they face the challenge of heat accumulation within their internal components. Therefore, heat dissipation technology is essential for the future evolution of electronic devices. Graphene, which dissipates heat efficiently, is attracting attention as a heat dissipation material due to its ultra-thin, lightweight, and flexible properties.

This discovery confirms that graphene is promising not only for dissipating heat but also for thermal management, which involves controlling the direction in which heat is dissipated. These properties are expected to be applied in the development of various fields, including next-generation electronics, energy, telecommunications, and medicine.

What is Graphene? Graphene is a sheet of carbon atoms bonded in a honeycomb lattice. Graphite, which is used in pencil leads, consists of layers of graphene. Because it is only one atom thick, it is extremely thin and lightweight, while also possessing very high strength and flexibility.

Furthermore, due to its high crystallinity, it is known to conduct heat extremely well. For example, while silver has the highest thermal conductivity among metals, graphene exhibits a thermal conductivity approximately 10 times higher.

Mechanism of Mesh-Structured Graphene In this study, we attempted to control the thermal conductivity properties by creating a regular structure on graphene at an extremely small, nanometer[*] scale.

Normally, when a structure is miniaturized, thermal conductivity decreases. In fact, for ribbon-shaped graphene, the narrower the width, the harder it is for heat to be conducted.

On the other hand, it was found that for mesh-structured graphene, miniaturization conversely increases thermal conductivity. This is thought to be the result of heat flows overlapping and strengthening each other like waves due to the mesh-like miniaturization. Such a phenomenon has previously only been observed at cryogenic temperatures approaching -273°C, so confirming it at room temperature is a major achievement.

At the same time, it was shown that thermal conductivity can be changed by adjusting the width of the graphene, suggesting the possibility of controlling heat flow by varying the structure in different locations within a graphene device.

By applying this technology, it is expected that heat flow control mechanisms based on entirely new principles can be designed.

Figure: (a) Schematic diagram of mesh-structured graphene and (b) ribbon-shaped graphene. (c) In mesh-structured graphene, it is believed that the waves conducting heat overlap and strengthen each other, resulting in increased thermal conductivity.

[*] A nanometer (nm) is a unit of length representing one-billionth of a meter (m). The thickness of a human hair is approximately 0.1 mm, and 1 nm is 100,000 times smaller than that.