Fabrication of bifacial wafer-scale silicon nanowire arrays with ultra-high aspect ratio through controllable metal-assisted chemical etching

Abstract

Bifacial wafer-scale silicon nanowire arrays have been prepared through controllable deposition and metal-assisted chemical etching. Highly uniform silicon nanowire arrays with ultra-high aspect ratio have been obtained on both sides of the silicon wafer. The effects of Ag, HF, and H2O2 on the formation mechanism have been systematically investigated. The results indicated that the influence of H2O2 on the length of silicon nanowires, the surface density of arrays and the thickness of silicon wafer is more obvious than that of HF. Furthermore, the relationship between the length of silicon nanowires and the molar ratio of HF/H2O2 has been investigated. It demonstrated that the length of silicon nanowires is proportional to ρ when the concentration of HF in the etchant is constant, but in inversely proportion to ρ when the concentration of H2O2 is constant, where ρ is defined as [HF]/( [HF]+ [H2O2]). This strategy will be beneficial and revelatory for fabrication of bifacial solar cells based on this wafer-scale silicon nanowire arrays.