Abstract
In this work, we use a two-step metal-assisted chemical etching method to produce films of silicon nanowires shaped in micrograins from metallurgical-grade polycrystalline silicon powder. The first step is an electroless plating process where the powder was dipped for few minutes in an aqueous solution of silver nitrite and hydrofluoric acid to permit Ag plating of the Si micrograins. During the second step, corresponding to silicon dissolution, we add a small quantity of hydrogen peroxide to the plating solution and we leave the samples to be etched for three various duration (30, 60, and 90 min). We try elucidating the mechanisms leading to the formation of silver clusters and silicon nanowires obtained at the end of the silver plating step and the silver-assisted silicon dissolution step, respectively. Scanning electron microscopy (SEM) micrographs revealed that the processed Si micrograins were covered with densely packed films of self-organized silicon nanowires. Some of these nanowires stand vertically, and some others tilt to the silicon micrograin facets. The thickness of the nanowire films increases from 0.2 to 10 μm with increasing etching time. Based on SEM characterizations, laser scattering estimations, X-ray diffraction (XRD) patterns, and Raman spectroscopy, we present a correlative study dealing with the effect of the silver-assisted etching process on the morphological and structural properties of the processed silicon nanowire films.
Highlights
For almost two decades, the largest parts of silicon nanostructures that have been performed were porous silicon using silicon wafers as a starting material
Results and discussion we try to elucidate the chemical mechanism occurring during each step of metal-assisted chemical etching (MACE)
We propose a correlative explanation stressing the mutual effect between etching time, grain size distribution (GSD) evolution, X-ray diffraction (XRD) patterns, and Raman spectra
Summary
The largest parts of silicon nanostructures that have been performed were porous silicon (pSi) using silicon wafers as a starting material. The attention of several researchers and industrials has been gradually swerved from pSi to silicon nanowires (SiNWs). Due to their good monocrystalline structure and electrical properties, SiNWs have been broadly explored for nanoscale electronic devices [1,2]. Microstructured silicon in wire shape is a good candidate to replace carbon lithiumion batteries. SiNWs would be able to overcome problems caused by huge volume expansion during lithiation, enabling larger capacity and longer stability [3,4]. In addition to the excellent biodegradability and biocompatibility of silicon dioxide [5,6], SiNWs exhibit a relatively high surface-
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