Simple fabrication of ultrahigh aspect ratio nanostructures for enhanced antireflectivity

Abstract

In this work, the authors present a novel fabrication process to create periodic nanostructures with aspect ratio as high as 9.6. These nanostructures reduce spectral reflectance of silicon to less than 4% over the broad wavelength region from 200 to 2000 nm. At the visible range of the spectrum, from 200 to 650 nm, reflectivity is reduced to less than 0.1%. The aspect ratio and reflectance performance that the authors achieved have never been reported before for ordered tapered nanostructures, to our knowledge.

Microstructured Ultra-black Thin Stainless-Steel Sheets Fabricated by Sagnac Interferometric-Based Ultrafast Laser Patterning

“…The shape of the nanostructures with a higher aspect ratio plays a crucial role in reducing the reflectivity. 18,22 Researchers have adopted different methods to fabricate these plasmonic structures by using lithography techniques, 23−26 chemical etching, plasma etching technique, 27 coating carbon nanotubes, 20 laser patterning, and a few combinations of methodologies. 28 Lithography and electron beam technologies are best at the fabrication of high-resolution patterns, but they require a high investment, have expensive operational costs, and are not easy to print in large areas.…”

“…The structural characteristics of shaped micro–nanostructures offer a complex and graded refractive index (RI) that can satisfy anti-reflectivity over a large bandwidth by geometrically trapping nearly all the photons incident on them, which is further enhanced with surface plasmon resonance coupling. , Researchers have demonstrated antireflective nanostructures both in periodic and random structures , in semiconductors, the latter being more effective for broadband performance. The shape of the nanostructures with a higher aspect ratio plays a crucial role in reducing the reflectivity. , Researchers have adopted different methods to fabricate these plasmonic structures by using lithography techniques, − chemical etching, plasma etching technique, coating carbon nanotubes, laser patterning, and a few combinations of methodologies . Lithography and electron beam technologies are best at the fabrication of high-resolution patterns, but they require a high investment, have expensive operational costs, and are not easy to print in large areas.…”

Fabrication of Cross-Sinusoidal Anti-Reflection Nanostructure on a Glass Substrate Using Imperfect Glass Imprinting with a Nano-Pin Array Vitreous Carbon Stamp

“…A high aspect ratio (HAR) cone-shape nanostructure is preferable for the realization of a gradually changing refractive index AR nanostructure [18]. To pattern the HAR cone shape nanostructure on a glass substrate via the glass imprinting process, a stamp with an HAR negative cone shape nanostructure is required.…”

Periodic nanostructures on unpolished substrates and their integration in solar cells

“…However, according to the effective medium theory (EMT) [13], when the interface between two media is patterned with periodic motifs smaller than the wavelength of light, there is a gradual variation in terms of refractive index that reduces light reflection. Recently, we have reported the fabrication of periodic high aspect-ratio nanocones with an almost perfect broadband matching between air and silicon [14]. In the fabrication process, laser interference lithography (LIL) and reactive ion etching (RIE) have been used, allowing control of the pitch, size and geometry of the final structures [14].…”

“…Recently, we have reported the fabrication of periodic high aspect-ratio nanocones with an almost perfect broadband matching between air and silicon [14]. In the fabrication process, laser interference lithography (LIL) and reactive ion etching (RIE) have been used, allowing control of the pitch, size and geometry of the final structures [14].…”