Theory explains how new material could improve electronic shelf life

Much of modern technology is based on silicon's use as a semiconductor material, but research recently published in the journal Nature Materials shows that graphene conducts heat about 20 times faster than silicon.

“Heat is generated every time a device computes,” said “Dr. Kyeongjae “KJ” Cho, associate professor of materials science and engineering and physics at UT Dallas and one of the paper's authors. “For example a laptop fan pumps heat out of the system, but heat removal starts with a chip on the inside. Engineered graphene could be used to remove heat – fast.”

It was demonstrated in 2004 that graphite could be changed into a sheet of bonded carbon atoms called graphene, which is believed to be the strongest material ever measured. Although much research has focused on the strength and electronics of the material, Cho has been studying its thermal conductivity.

As electronics become more complex and decrease in size, the challenge to remove heat from the core becomes more difficult, he said. Desktop and laptop computers have fans. Smaller electronic devices such as cellphones have other thermoelectric cooling devices.

“The performance of an electronic device degrades as it heats up, and if it continues the device fails,” said Cho, also a visiting professor at Seoul National University in South Korea. “The faster heat is removed, the more efficient the device runs and the longer it lasts.”

Research assistant Hengji Zhang of UT Dallas is also an author of the paper. Cho and Zhang have published prior papers in the Journal of Nanomaterials and Physical Review B about graphene's thermal conductivity. For the Nature Materials paper, researchers at UT Austin conducted an experiment about graphene's heat transfer. They used a laser beam to heat the center of a portion of graphene, then measured the temperature difference from the middle of the graphene to the edge. Cho's theory helped explain their findings.

“We refined our modeling work taking into account their experimental conditions and found we have quantitative agreement,” Cho said. “By understanding how heat transfers through a two-dimensional graphene system, we can further manipulate its use in semiconductor devices used in everyday life.” For this purpose, Cho and Zhang are preparing a follow-up article on how to control the thermal conductivity in graphene.

The Nature Materials experiment was done in collaboration with Shanshan Chen and Weiwei Cai of Xiamen University in Xiamen China and UT Austin; Qingzhi Wu, Columbia Mishra and Rodney Ruoff of UT Austin; Junyong Kang also of Xiamen University; and Alexander Balandin of the University of California, Riverside.

The research was supported by the National Science Foundation, Office of Naval Research, National Natural Science Foundation of China, Semiconductor Research Corporation, NRF of Korea, and W.M. Keck Foundation.