Gate-tunable near-field heat transfer (Conference Presentation)

Abstract

Within the last two decades, it has been theoretically shown and experimentally measured that the radiative heat transfer between bodies in the near-field significantly exceeds the blackbody limit. This enhancement in heat transfer arises from evanescent surface waves, for example surface plasmon and surface phonon polaritons, that can tunnel between bodies at different temperatures. This result holds promise for applications in nano-imaging and lithography, thermophotovoltaics, nanoscale refrigeration and thermal circuitry. Although significant progress has been made in near-field heat transfer using passive materials, such as plasmonic metals and polar dielectrics, realizing actively tunable near-field heat transfer modules is of fundamental importance for controlling the photon heat flux. In this talk, analogously to its electronic counterpart, the metal-oxide-semiconductor (MOS) capacitor, we propose a thermal switching mechanism based on accumulation and depletion of charge carriers in an ultra-thin plasmonic film, via application of external bias. In our proposed configuration, the plasmonic film is placed on top of a polaritonic dielectric material that provides a surface phonon polariton thermal channel, while also ensuring electrical insulation for application of large electric fields. The variation of carrier density in the plasmonic film enables the control of the surface plasmon polariton thermal channel. We show that the interaction of the surface plasmonic mode with the surface phonon polariton significantly enhances the net heat transfer. We study SiC as the oxide and explore three classes of gate-tunable plasmonic materials: transparent conductive oxides, doped semiconductors, and graphene, and theoretically predict contrast ratios as high as 225%.