Role of Remote Interfacial Phonon (RIP) Scattering in Heat Transport Across Graphene/SiO₂ Interfaces

Abstract

Heat transfer across interfaces of graphene and polar dielectrics (e.g. SiO 2 ) could be mediated by direct phonon coupling, as well as electronic coupling with remote interfacial phonons (RIPs). To understand the relative contribution of each component, we develop a new pumpprobe technique, called voltage-modulated thermoreflectance (VMTR), to accurately measure the change of interfacial thermal conductance under an electrostatic field. We employed VMTR on top gates of graphene field-effect transistors and find that the thermal conductance of SiO 2 /graphene/SiO 2 interfaces increases by up to ΔG  0.8 MW m -2 K -1 under electrostatic fields of <0.2 V nm -1 . We propose two possible explanations for the observed ΔG. First, since the applied electrostatic field induces charge carriers in graphene, our VMTR measurements could originate from heat transfer between the charge carriers in graphene and RIPs in SiO 2 . Second, the increase in heat conduction could be caused by better conformity of graphene interfaces un-

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

“…We find that for intrinsic Pd/graphene/Pd interfaces prepared by thermal evaporation, electrons do not play an active role in the heat conduction across metal contacts on pristine graphene. Together with our previous finding that scattering of electrons by remote interfacial phonons does not significantly enhance thermal conductance of graphene/SiO 2 interfaces, we conclude that additional heat transport by electrons is not a viable route to enhance the thermal conductance of pristine graphene interfaces. Interestingly, we find that the thermal conductance G of the sandwiched structure prepared by radiofrequency (rf) magnetron sputtering is enhanced from 42 to 300 MW m −2 K −1 .…”

“…a) Temperature dependence of the thermal conductance G of interfaces of Pd/trG/Pd (solid symbols, this work), compared to that of Al/trG/Cu (open circles), Au/exG/SiO 2 (open left triangles). The top metal layer of the Pd/trG/Pd interfaces was deposited either by rf magnetron sputtering (red) or by thermal evaporation (blue).…”

Thickness-dependent Kapitza resistance in multilayered graphene and other two-dimensional crystals

“…In particular, the lattice thermal boundary conductance (TBC) G, defined as G = R −1 K , depends on the lattice properties of the materials as well as their van der Waals (vdW) interaction. Although variations in the Kapitza resistance have been attributed [8][9][10][11] to differences in interfacial roughness and contact as well as to remote phonon scattering [12,13], there is increasing evidence from molecular dynamics (MD) simulations [14][15][16][17][18][19] and experiments [20][21][22][23] that the TBR between an unencapsulated or bare thin film and its substrate has a strong thickness dependence for which we have no satisfactory explanation especially in a layered crystal such as graphene. It has been observed [14] that the TBR for fewlayer graphene decreases significantly as the film thickness (or the number of layers N ) increases and asymptotically converges to a fixed value when N is large.…”

“…This can be explained by noting that the transmission coefficient function in Eq. (2) can be expressed as the sum of the transmission by each phonon branch, i.e., (13) where D n (q, ω) is the summand in Eq. (10) and is proportional to the weight f n which scales as N −1 .…”

Remarkable Reduction of Interfacial Thermal Resistance in Nanophononic Heterostructures

“…besides the material's own thermal conductivity, the interfacial thermal conductance is becoming more and more important with scaling down of the devices, and has continuously attracted intensive research interests. [17][18][19][20][21][22][23][24][25][26] In principle, there always exists contact thermal resistance when phonons transport across the interface between two dissimilar materials. A large number of studies have been done to understand the interfacial thermal conductance of various types of interface, including mass-mismatched solidsolid interface, [27,28] hard-soft materials interface, [29,30] solid-liquid interface, [31] metal-nonmetal interface considering electron-phonon interaction, [32,33] and solid-gas interface.…”