Session: 03-03: Micro/Nanoscale Interfacial Transport Phenomena

Paper Number: 134711

134711 - Graphene Plays a Role of Bridge in the Heat Transfer From Silicon to Water 

Abstract: 

Heat dissipation is increasingly becoming an important factor restricting chip performance. A cooling system using liquid as heat transfer medium may help improve the heat dissipation bottleneck of chips. However, the interface thermal resistance of solid-liquid interface is quite large, which limits the actual performance of this kind of system. With high level of thermal conductivity and a similar structure compared with silicon, graphene has the potential to be used in chips to help transfer heat from solid to liquid. However, the measurement and understanding of the interface thermal conductivity of silicon-graphene-water interface is a prerequisite for its application. In this research, as a basement, a water-silicon system was established and the interface thermal conductivity was measured. Then, a graphene-silicon system and a water-graphene-silicon system were established, and the thermal interface conductivity were measured using Raman spectrum respectively. The Raman shifts of G peak in different layers of graphene were calibrated and exhibited good linearity. For silicon-graphene systems, 50x and 100x objective lens were used to focus laser on the surface of graphene. The power of laser was changed to get the correlation between absorb power and Raman shifts. For water-silicon system, the laser was focused on the silicon instead. Then, a water film was added and a 50x objective lens was used to repeat measurement as a comparison. A stable heat transfer model was used to fit curves and get results. The thermal interface conductivity of water-silicon interface is 0.816 MW/(m²∙K). For single-layer, bilayer, triple-layer and 5-layer graphene, we got the thermal interface conductivity of silicon-graphene-water interface equal to 0.733 MW/(m²∙K), 3.43 MW/(m²∙K), 8.11 MW/(m²∙K) and 12.4 MW/(m²∙K) respectively. Compared to water-silicon system, the interface thermal conductivity of silicon-SLG-water is larger due to the introduction of extra depth. However, as the number of graphene layers increases from 1 to 5, the interface thermal conductivity declines and even lower than that of water-silicon system, which implies that graphene may help heat transfer from silicon to water. MD simulations were used to clarify its mechanism. To construct the model, a silicon film and a water film were created. Then, a different number of graphene layers, ranging from one to six, were inserted to the interface separately. A heat pulse using Langevin thermostat was applied to the graphene and then the whole system was put into a NVE ensemble to achieve equilibrium. For water-silicon model, the heat pulse was applied to silicon instead. The transient process was recorded and temperature difference curve was fitted. The interface thermal conductivity derived from MD simulations is consistent with the experiment. Then, the VDOS ranging across different frequencies was calculated in each model. There exists a large mismatch of VDOS between silicon and water, which leads to a large interface thermal resistance. We find that, when few layers of graphene are added, the mismatch is improved. That is to say, graphene plays a role of bridge between solid and liquid and decreases the total thermal resistance. Triple-layer graphene has a good total capacity to transfer heat from solid to liquid and may play an important role in electronic devices cooling systems.

Presenting Author: Weigang Ma Tsinghua University

Presenting Author Biography: Weigang Ma received the B.E. (2006) and Ph. D (2012) degrees from Tsinghua University. He is an Associate Professor, Department of Engineering Mechanics, Tsinghua University, China. His current interests mainly focus on micro/nanoscale transport and energy conversion.

Authors:

Weigang Ma Tsinghua University
Tao Ding Tsinghua University