  Near-field radiative heat transfer (NFRHT) between dissimilar materials
supporting surface polaritons in the infrared is of critical importance for
applications such as photonic thermal rectification and near-field
thermophotovoltaics. Here, we measure NFRHT between millimetersize surfaces
made of 6H-SiC and doped Si, respectively supporting surface phonon-polaritons
(SPhPs) and surface plasmon-polaritons (SPPs) in the infrared, separated by a
150-nm-thick vacuum gap spacing maintained via SiO2 nanopillars. For purpose of
comparison, measurements are also performed between two doped Si surfaces. The
measured radiative flux is in good agreement with theoretical predictions based
on fluctuational electrodynamics. A flux enhancement beyond the blackbody limit
of ~ 8.2 is obtained for the SiC-Si sample, which is smaller than the
enhancement for the Si-Si sample (~ 12.5) owing to the spectral mismatch of the
SiC and Si light lines, and SPhP and SPP resonances. However, due to lower
losses in SiC than Si and weaker SPhP-SPP coupling than SPP coupling, the
near-field enhancement for the SiC-Si sample exhibits a more pronounced
monochromatic behavior with a resonant flux that is ~ 5 times larger than the
resonant flux for the Si-Si sample. This work demonstrates that it is possible
to modulate NFRHT via surface polariton coupling, and will accelerate the
development of energy conversion and thermal management devices capitalizing on
the near-field effects of thermal radiation between dissimilar materials.
