Enhanced Surface Properties of Light-Trapping Si Nanowires Using Synergetic Effects of Metal-Assisted and Anisotropic Chemical Etchings

Abstract

Metal-assisted chemical etching (MACE) has been widely explored for developing silicon (Si)-based energy and optical devices with its benefits for low-cost and large-area fabrication of Si nanostructures of high aspect ratios. Surface structures and properties of Si nanostructures fabricated through MACE are significantly affected by experimental and environmental conditions of etchings. Herein, we showed that surfaces and interfacial energy states of fabricated Si nanowires can be critically affected by oxidants of MACE etching solutions. Surfaces of fabricated Si nanowires are porous and their tips are fully covered with lots of Si nano-sized grains. Strongly increased photoluminescence (PL) intensities, compared to that of the crystalline Si substrate, are observed for MACE-fabricated Si nanowires due to interfacial energy states of Si and SiOx of Si nano-sized grains. These Si grains can be completely removed from the nanowires by an additional etching process of the anisotropic chemical etching (ACE) of Si to taper the nanowires and enhance light trapping of the nanowires. Compared with the MACE-fabricated Si nanowires, ACE-fabricated tapered Si nanowires have similar Raman and PL spectra to those of the crystalline Si substrate, indicating the successful removal of Si grains from the nanowire surfaces by the ACE process.

Ultralow Optical and Electrical Losses via Metal‐Assisted Chemical Etching of Antireflective Nanograss in Conductive Mesh Electrodes

“…Figure compares the absorptions when light illuminates short and long SiNG. UV light generated electron–hole pairs mostly in the top portion of the SiNG [ 28,57 ] because of the shallow penetration depth. In the case of short SiNG, carriers generated by UV light were separated by the Schottky junction and collected before recombination.…”

“…As an alternative to RIE, metal‐assisted chemical etching (MacEtch) has been suggested. [ 15–28 ] It can fabricate high‐aspect‐ratio semiconductor nanostructures without causing crystal defects because it uses wet‐based chemical processes. Patterned metal catalysts are deposited on a semiconductor that is immersed in an etchant composed of an acid and oxidant.…”

Newly Developed Broadband Antireflective Nanostructures by Coating a Low-Index MgF2 Film onto a SiO2 Moth-Eye Nanopattern

“…All simulations were performed under periodic boundary conditions in the x - and y -directions and under perfectly matched layer boundary conditions in the z -direction. All simulated reflectance values of the various 2D periodic-patterned structures were adjusted by the low-pass filtering method to eliminate overestimated artificial interference. , Fitting conditions of the refractive index of each layer were obtained from the measured results or from the literature; the refractive index and extinction coefficient value of the ITO layer were measured using an ellipsometer; and these values of the MgF 2 layer were obtained from the literature …”

Fabrication of Needle-Like Silicon Nanowires by Using a Nanoparticles-Assisted Bosch Process for Both High Hydrophobicity and Anti-Reflection

“…Their diameter lies in the range of nanometers to a few hundred nanometers [ 11 ], while their height can be as large as several micrometers [ 12 ]. Apart from the bottom-growth approaches, various patterning and dry etching processes have also been developed to realize nanowire fabrication with semiconductors [ 13 , 14 , 15 ]. Interestingly, most of the reported nanowire arrays are patterned by using electron-beam and holographic lithography techniques [ 16 ], which are attractive in generating a periodic pattern with a high degree of uniformity.…”