This paper describes an experimental investigation on the infrared radiative properties of heavily doped Si at room temperature. Lightly doped Si wafers were ion-implanted with either boron or phosphorus atoms, with dosages corresponding to as-implanted peak doping concentrations of 1020 and 1021 cm−3; the peak doping concentrations after annealing are 3.1×1019 and 2.8×1020 cm−3, respectively. Rapid thermal annealing was performed to activate the implanted dopants. A Fourier-transform infrared spectrometer was employed to measure the transmittance and reflectance of the samples in the wavelength range from 2 μm to 20 μm. Accurate carrier mobility and ionization models were identified after carefully reviewing the available literature, and then incorporated into the Drude model to predict the dielectric function of doped Si. The radiative properties of doped Si samples were calculated by treating the doped region as multilayer thin films of different doping concentrations on a thick lightly doped Si substrate. The measured spectral transmittance and reflectance agree well with the model predictions. The knowledge gained from this study will aid future design and fabrication of doped Si microstructures as wavelength selective emitters and absorbers in the midinfrared region.
Magnetic polaritons that couple electromagnetic waves with magnetic excitation can be used for tailoring the radiative properties of materials in energy-harvesting and other applications. Previous studies used metallic microstructures to induce magnetic responses. With rigorous coupled-wave analysis (RCWA), transmission enhancement with a SiC slit array and coherent thermal emission with a SiC deep grating is theoretically demonstrated in the infrared within the phonon absorption band. The field distributions and the agreement in the resonance frequencies predicted from both RCWA and LC circuit models strongly suggest that magnetic polaritons exist in the SiC microstructures. This type of magnetic polariton is mediated by vibration of atoms in polar materials (i.e., optical phonons), rather than by free electrons in metals. Our results suggest that phonon-mediated magnetic polaritons have promising applications such as filters and selective coherent emitters in the infrared spectral region.
Excitation of surface plasmons enables super-Planckian thermal radiation far beyond the blackbody limit. By patterning a single layer of graphene sheet into ribbons, the closed circular dispersion of graphene plasmons is opened to become hyperbolic, leading to broadband singularities of density of states. Extremely high-k evanescent waves can now couple with hyperbolic graphene plasmons. Consequently, a giant enhancement of the near-field radiative heat flux, by more than one order of magnitude, is demonstrated in this study using rigorous numerical simulations. The findings may open promising pathways for highly efficient thermal management, energy harvesting, and sub-wavelength thermal imaging.
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