Effects of Preparation on the Silicon Nanowires Grown By Electroless Etching

Highly oriented SiNWs arrays prepared by electroless etching method can significantly suppress light reflection across a broad spectrum [1]. The antireflective nature of Silicon nanowires (SiNW’s) revealed by their black color and dull appearances have drawn the attention of researchers [2]. Reflectivity studies on these show a significantly decrease in optical reflectivity down to 1.3% for 10 µm long SiNWs arrays [3]. Electroless etching is a top-down technique for growing SiNWs and does not need costly and expensive equipment to grow SiNWs as bottom-up methods usually do.

The electroless process begins with the cleaning of silicon substrates. They were cleaned in acetone, methanol and deionized water, then blow-dried with N₂. They are dipped in hydrofluoric acid (HF) 49% solution for 1 min to remove any remaining oxide.

The silicon (Si) wafers are dipped for 15 minutes at room temperature in an electroless solution prepared in a petri dish containing silver nitrate (AgNO₃) and hydrofluoric acid (HF) [4].

The substrates are dipped and galvanic reactions disperse silver ions on their surface, losing silicon as SiF₆. As a consequence of this etching process, the removal of Si via Ag ions results in vertically aligned arrays of SiNWs covered with silver dendrites.

At the end of the etching process, the samples were dipped in two baths of deionized water and placed in diluted nitric acid (HNO₃) 20% to remove the Ag dendrite layer formed on top of the SiNW arrays. Reflectance on different methods to remove the residual silver particles from SiNW’s when using an unstirred, stirred and sonicated diluted nitric acid (HNO₃) 20% solution are presented Fig 1.