Graphene Layer Number-Dependent Heat Transport across Nickel/Graphene/Nickel Interfaces

As a typical two-dimensional material, graphene (Gr) has shown great potential to be used in thermal management applications due to its ultrahigh in-plane thermal conductivity (k). However, low interface thermal conductance (ITC) between Gr and metals to a large extent limits the effective heat dissipation in Gr-based devices. Therefore, having a deep understanding on heat transport at Gr-metal interfaces is essential. Because of the semimetallic nature of Gr, electrons would possibly play a role in the heat transport across Gr-metal interfaces as heat carriers, whereas, However, how much the electron can participate in this process and how to optimize the total ITC considering both electron and phonon transportations have not yet been revealed yet. Therefore, in this work, hydrogenation-treated Gr (H-Gr) was sandwiched by nickel (Ni) nanofilms to compare with the samples containing pure Gr for investigating the interfacial electron behaviors. Moreover, both Gr and H-Gr sets of the samples were prepared with different layer numbers (N) ranging from 1 to 7, and the corresponding ITC was systematically studied based on both time-domain thermoreflectance measurements and theoretical calculations. We found that a larger ITC can be obtained when N is low, and the ITC may reach a peak value when N is 2 in certain circumstances. The present findings not only provide a comprehensive understanding on heat transport across Gr-metal interfaces byconsidering a combined effect of the interfacial interaction strength, phonon mode mismatch, and electron contributions, but also shed new lights on interface strucure optimiazations of Gr-based devices.

Automated summary

Graphene has great potential for thermal management applications due to its high thermal conductivity. However, the low interface thermal conductance between graphene and metals limits its effective heat dissipation. In this study, the interfacial electron behaviors were investigated by comparing hydrogenation-treated graphene with pure graphene, and the effect of graphene layer numbers on the interfacial thermal conductance was systematically studied. The results showed that a larger interfacial thermal conductance can be obtained with lower layer numbers.