Infrared emitting nanostructures for highly efficient microhotplates

A highly emissive Si-based microhotplate based on self-organizing nanostructures is presented. The silicon was structured by a self-masking deep reactive ion etching process resulting in needle-like non-periodical microstructures. Evaporated platinum settles in a kind of glancing angle deposition as well-defined nanocrystals on the silicon microstructures. Finite-difference time-domain simulation allowed the evaluation of the ideal platinum thickness for maximized infrared absorption and emission. We measured the hemispherical spectral transmittance and reflectivity of the fabricated surfaces and found the hemispherical spectral absorbance to be up to 0.97 in the investigated wavelength range. To demonstrate the advantages of these micro-nano-structures, we present the fabrication and characterization of a thermal infrared hotplate-emitter. With integrated Pt-on-Si-needles, the emitter shows a 2.6 times higher IR emission without wavelength-dependent interference patterns as compared to an uncoated Si-based emitter at the same membrane temperature.