Electronic control of heat flow across graphene interfaces
We experimentally demonstrate fast control of heat conduction using electrostatic fields. Heat flow modulation is achieved through gate control perpendicular to the channel of top-gated graphene field-effect transistors (GFETs), and is monitored by a newly developed technique, voltage-modulated thermoreflectance (VMTR). We find that the thermal conductance of SiO2/graphene/SiO2 interfaces increases by up to {\Delta}G~0.8 MWm-2K-1 under electrostatic fields of <0.2 Vnm-1. We propose two possible explanations for the observed {\Delta}G. First, since the applied electrostatic field induces charge carriers in graphene, our VMTR measurements could originate from heat transfer between the induced charge carriers and surface polar phonons in SiO2 via remote interfacial phonon (RIP) scattering. Second, the increase in heat conduction could be engendered by better conformity of graphene interfaces under electrostatic pressure exerted by the induced charge carriers. Regardless of the origins of the observed {\Delta}G, our VMTR measurements establish an upper limit for heat transfer from unbiased graphene to SiO2 substrates via RIP scattering for the graphene-SiO2 interface; i.e., only <2 % of the interfacial heat transport is facilitated by RIP scattering even at a carrier concentration of ~4x10^12 cm-2. Our findings also inaugurate a new mechanism to control and modulate heat transport, which could facilitate realization of phononic devices.