High transparent mid-infrared silicon “window” decorated with amorphous photonic structures fabricated by facile phase separation

Abstract

High transparency in the infrared (IR) region is desirable for most common IR materials and devices, due to their high interfacial reflectance, resulting from the high refractive indices of constituent substances. Herein, a new strategy, with using phase-separated polystyrene (PS)/polymethylmethacrylate (PMMA) blends as masks, is proposed to fabricate subwavelength structures for Si with significantly enhanced mid-IR transmission. Maximum transmittance approaching to 70% and 90% are achieved with single and double- side structured Si respectively. The fabricated subwavelength structures are short-range ordered amorphous photonic structures (APSs). By using different spin-coating speeds and molar ratios of PS to PMMA and by adjusting the etching duration time, tunable enhanced transmission are also obtained. The good performance of high transmission is confirmed by mid-IR thermal imaging experiments. Furthermore, the enhanced transmission is effective over a wide range of incident angles up to 50° and well maintained at high temperatures up to 600 °C.

Review of Surface Modification Technologies for Mid‐Infrared Antireflection Microstructures Fabrication

“…Adapted with permission. [ 86 ] Copyright 2018, The Optical Society. e) RIE on Si using a mask produced by colloidal lithography technique, f) RIE on GaAs using a mask produced by colloidal lithography technique, and RIE on Ge using a mask produced by colloidal lithography technique (g,h).…”

“…The first approach speeds up the masking process using the self‐organization properties of polymethylmethacrylate (PMMA) and polystyrene (PS) mixture to create a random pattern mask for ARM fabrication. [ 86 ] The sample is then immersed into acetic acid to remove the PMMA film, thereby leaving a patterned PS‐phase film behind. However, the resulting structured PS film cannot be directly used as etching masks because it is not sufficiently thick to be depleted in a dry etching process.…”

“…The authors in ref. [86] deposited a 5‐nm mask of chromium onto the PS mask and then immersed the sample into cyclohexane to remove the chromium‐coated PS parts, thereby forming a complementary patterned chromium hard mask. After dry etching, ARM is obtained on the silicon substrate (Figure 8c,d) thereby providing an 89% transmittance increase in the 3–10 m range (Figure 9b).…”

Engineering the reciprocal space for ultrathin GaAs solar cells

“…24 QR-PC structures are good candidates for self-assembly fabrication, such as spinodal decomposition based methods, because they control the reciprocal space. 30,35,36 In summary, the thickness and reciprocal space defines the absorption of the QR structure. The real space has more degrees of freedom and therefore differences, but the final absorption is defined by the target reciprocal space: k 1 , k 2 and ∆m.…”

Silicon- and Graphene-based FETs for THz technology

“…Teflon windows ensure that the sample is only excited by the THz radiation, since they show good transmittances on these frequency ranges making them ideal components for IR and THz applications. Conversely, they exhibit close to zero transmittance in the visible range [25] ensuring that the devices are only excited by the incoming THz radiation. The samples placed on this system are held in vacuum and cooled by a Pulse Tube refrigerator.…”