Large-area fabrication of high aspect ratio tantalum photonic crystals for high-temperature selective emitters

Abstract

Articles you may be interested inFabrication of transferrable, fully suspended silicon photonic crystal nanomembranes exhibiting vivid structural color and high-Q guided resonanceThe authors present highly selective emitters based on two-dimensional tantalum (Ta) photonic crystals, fabricated on 2 in. polycrystalline Ta substrates, for high-temperature applications, e.g., thermophotovoltaic energy conversion. In this study, a fabrication route facilitating large-area photonic crystal fabrication with high fabrication uniformity and accuracy, based on interference lithography and reactive ion etching is discussed. A deep reactive ion etch process for Ta was developed using an SF 6 =C 4 F 8 based Bosch process, which enabled us to achieve $8:5 lm deep cavities with an aspect ratio of $8, with very steep and smooth sidewalls. The thermal emitters fabricated by this method show excellent spectral selectivity, enhancement of the emissivity below cut-off approaching unity, and a sharp cut-off between the high emissivity region and the low emissivity region, while maintaining the low intrinsic emissivity of bare Ta above the cut-off wavelength. The experimental results show excellent agreement with numerical simulations.

Three-dimensional metallo-dielectric selective thermal emitters with high-temperature stability for thermophotovoltaic applications

“…Therefore, in order to attain the desired emission selectivity and high-temperature stability, photonic selective emitters rely on refractory metals, such as tungsten [5] and tantalum [10,11]. Unfortunately, it turns out that micro-and nano-structures are unstable at temperatures much below the melting point of these materials due to, mainly, recrystallization and surface diffusion effects [12,13].…”

“…For instance Yablonovitch already proposed in his pioneering work on photonic crystals [7] that spontaneous emission could be inhibited within the photonic band gap regions. Since then, several structures have been proposed for selective thermal emission in the TPV context such as 1D metal-dielectric stacks [8], 2D arrays of metallic microcavities [4,9,10], and metallic 3D photonic crystals [3,6]. Metallic structures are typically preferred as they naturally keep the emission low at long wavelengths, while the emissivity can be enhanced at shorter wavelengths through micro-structuring.…”

Enabling Ideal Selective Solar Absorption with 2D Metallic Dielectric Photonic Crystals

“…[13] In particular, two-dimensional metallic air photonic crystals (MAPhC) have been shown to selectively absorb light in the near-IR via cavity modes and withstand high temperatures greater than 1000°C; however, the acceptance angle is limited to ±30°, and the absorption in the visible spectrum is limited due to diffraction. [2,11,15] Metamaterial and plasmonic based absorbers have demonstrated wide angle absorption due to their subwavelength periodic structures; however high temperature stability and wafer-scalefabrication have yet to be shown. [1,3,[16][17][18][19] Here we present our 2D metallic dielectric photonic crystal (MDPhC) structure, which simultaneously demonstrates broadband (visible to near-IR) absorption, omnidirectional absorption, wafer-scale fabrication, and high temperature robustness.…”

“…Recent developments of metal based selective absorbers have demonstrated 1D, 2D, and 3D metallic photonic crystal structures capable of tailoring the absorption spectrum. [2,[8][9][10][11][12][13][14] One dimensional metal dielectric stacks have demonstrated promising solar absorbing properties but are unstable at temperatures greater than approximately 600°C. [13] In particular, two-dimensional metallic air photonic crystals (MAPhC) have been shown to selectively absorb light in the near-IR via cavity modes and withstand high temperatures greater than 1000°C; however, the acceptance angle is limited to ±30°, and the absorption in the visible spectrum is limited due to diffraction.…”

“…[13] In particular, two-dimensional metallic air photonic crystals (MAPhC) have been shown to selectively absorb light in the near-IR via cavity modes and withstand high temperatures greater than 1000°C; however, the acceptance angle is limited to ±30°, and the absorption in the visible spectrum is limited due to diffraction. [2,11,15] Metamaterial and plasmonic based absorbers have demonstrated wide angle absorption due to their subwavelength periodic structures; however high temperature stability and wafer-scale…”