Novel Si nanostructures via Ag-assisted chemical etching route on single and polycrystalline substrates

Abstract

Silicon is the most widely used semiconductor material for electronics and energy related applications. Herein, different Si nanostructures with various shapes, sizes and morphologies are fabricated by a simple, low-cost and versatile metal‐assisted chemical etching (MACE) technique using Ag nanoparticles as a catalyst, deposited on Si surface. The influence of etching time, temperature and intrinsic properties of the silicon substrate (e.g., orientation, crystallinity) on the basic process are studied. Fast preparation of porous silicon (PSi) was achieved on Si 〈100〉 at room temperature after only 30 s of exposure to etching solution. Meanwhile increased etching time led to increase the pore diameter and a well-aligned SiNWs was obtained after 10 min. However, the exposure of Si 〈100〉 to the etching solution at 60 °C for only 2 min produced a homogenous and dense SiNWs layer. Additionally, the orientation of Si wafer was found to play a key role during the MACE process. Particularly, the MACE has no effect on Si 〈111〉 before 30 min whereas a zigzage PSi was formed. PSi nanostructures with straight and zigzag structures were successfully fabricated for the first time in addition to well-aligned, uniform and vertical Si nanowires (SiNWs) with smooth and polygonal shapes. The as-prepared Si nanostructures are characterized by various techniques including field emission-scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), UV–vis. and photoluminescence spectroscopy (PL). The optical properties of as-prepared Si nanostructures are enhanced and the reasons for this improvement and its correlation with the morphology difference are presented and discussed.