  We model near-field thermal emission from metasurfaces structured as
two-dimensional arrays of ellipsoidal SiC particles. The modeling approach is
developed from fluctuational electrodynamics and is applicable to systems of
ellipsoidal particles within the dipole limit. In all simulations, the radial
lengths of particles are restricted to the range of 10 to 100 nm, and
interparticle spacing is constrained to at least three times the particle
characteristic length. The orientation and dimensions of constituent
ellipsoidal particles are varied to tune localized surface phonon resonances
and control the near-field energy density above metasurfaces. Results show that
particle orientation can be used to regulate the relative magnitude of
resonances in the energy density and particle dimensions may be changed to
adjust the frequency of these resonances within the Reststrahlen band.
Metasurfaces constructed from particles with randomized dimensions display
comparatively broadband thermal emission rather than the three distinct
resonances seen in metasurfaces made with ellipsoidal particles of equivalent
dimensions. When the interparticle spacing in a metasurface exceeds about three
times the particle characteristic length, the spectral energy density above the
metasurface is dominated by individual particle self-interaction and can be
approximated as a linear combination of single-particle spectra. When
interparticle spacing is at the lower limit of three times the characteristic
length, however, multiparticle interaction effects increase, and the spectral
energy density above a metasurface deviates from that of single particles. This
work provides guidance for designing all-dielectric, particle-based
metasurfaces with desired near-field thermal emission spectra, such as thermal
switches.
