Negligible Electronic Contribution to Heat Transfer across Intrinsic Metal/Graphene Interfaces

Abstract

Despite the importance of high thermal conductance (i.e., low thermal resistance) of metal contacts to thermal management of graphene devices, prior reported thermal conductance (G) of metal/graphene interfaces are all relatively low, only 20-40 MW m -2 K -1 . One possible route to improve the thermal conductance of metal/graphene interfaces is through additional heat conduction by electrons, since graphene can be easily doped by metals. In this paper, we evaluate the electronic heat conduction across metal/graphene interfaces by measuring the thermal conductance of Pd/transferred graphene (trG)/Pd interfaces, prepared by either thermal evaporation or radio-frequency (rf) magnetron sputtering, over a wide temperature range of 80 ≤ T ≤ 500 K. We find that for the samples prepared by thermal evaporation, the thermal conductance of Pd/trG/Pd is 42 MW m -2 K -1 . The thermal conductance only weakly depends on temperature, which suggests that heat is predominantly carried by phonons across the intrinsic Pd/graphene interface. However, for Pd/trG/Pd samples with the top Pd films deposited by rf magnetron sputtering, we observe a significant increment of thermal conductance from the intrinsic value of 42 MW m -2 K -1 to 300 MW m -2 K -1 , and G is roughly proportional to T. We attribute the enhancement of thermal conductance to an additional channel of heat transport by electrons via atomic-scale pinholes formed in the graphene during the sputtering process. We

Thermal Boundary Conductance and Phonon Transmission in Hexagonal Boron Nitride/Graphene Heterostructures

“…Finally, the TBC predicted using α 12,fit is shown in Figure along with TBC for Ti/G, Ti/h‐BN, and h‐BN/G from our TDTR results. Various literature results for h‐BN/G, metal/G, and metal/graphite interfaces are also shown for comparison. The discrepancy between h‐BN/G results for the A‐DMM and PWA‐DMM models at low temperatures arises from the assumption of constant α 12 .…”

“…Also shown are previously reported values of h‐BN/G TBC from studies by Chen et al (open left purple triangle), Liu et al (open purple diamond), and Kim et al (open purple trapezoid) using Raman spectroscopy. For further comparison, TBC for various metal/G [Al/O‐G (open black square), Pd/G (open up black triangle), and Ag/G (open right black triangle) and Ti/graphite (open gray circles) interfaces are also shown.…”

Anisotropic model with truncated linear dispersion for lattice and interfacial thermal transport in layered materials

“…On one hand, the low thermal conductance across the basal planes could limit the performance of the nanodevices of layered materials. For example, heat dissipation from hot spots in graphene-based nanodevices is limited by the poor thermal conductance of graphene interfaces, [15][16][17][18] despite the high thermal conductivity along the basal planes. On the other hand, the poor thermal properties could lead to better performance of thermoelectric materials, in which low thermal conductivity enhances the thermoelectric figure of merit (ZT) and thus the efficiency of thermoelectric energy conversion.…”

Cross-plane thermal transport in graphene-based structures

“…Along with the extensive studies of metal/Gr/SiO2 interfaces, the metal/Gr/metal interfaces with metal substrates like Cu, Pd and W started to get attraction in recent years [40,41]. Huang et al [42] performed the TDTR measurements on the Pd/transferred Gr/Pd interface and reported a G of 300 MWm -2 K -1 at RT for the sample with radiofrequency (rf) 6 magnetron sputtering top Pd. This value is seven times larger than that with thermal evaporation top Pd (42 MWm -2 K -1 ).…”

“…Another reason may be the damage of graphene during the β-W sputtering progress, where additional channels of direct heat transport between the β-W films form and significantly enhance the thermal conductance of the interfaces. This damage enhanced phenomenon has been studied in the most recent work by Huang et al [42] In this work, they reported measurements on thermal conductance of Pd/trG/Pd interface with the top Pd prepared by either thermal evaporation or rf magnetron sputtering. The results shown that, G of the sample with the rf magnetron sputtering Pd is 300 MWm -2 K -1 at RT, seven times larger 35 than that with the thermal evaporation Pd (42 MWm -2 K -1 ).…”