Silver-Assisted Etching of Silicon Nanowires

Abstract

Silicon nanowires are attractive for photovoltaic applications where they can be used along with bulk silicon in an all-Si tandem solar cell. The larger band gap, caused by the quantum confinement effect in narrow silicon nanowires (< 5 nm), provides a more efficient light absorption. The most common processes for nanowire synthesis are rather expensive and require high temperatures, high vacuum and hazardous precursors. A simple and cheap method is the silver-assisted electroless Si etching process. A silicon substrate is selectively etched in HF based solutions with the help of silver particles which are deposited beforehand or in-situ. Both the etch process and the deposition of silver particles were studied. The silver nanoparticles were deposited by electroless deposition (galvanic displacement) from HF and non-HF containing solutions. The effects of silver coverage, Si doping and illumination on the Si etching process were investigated. The experimental observations were used to get more insight into the mechanism.

Study of the Properties of the Porous Silicon Synthesized by Ag Assisted Chemical Etching

“…In order to optimize the Ag particle deposition, a systematic study has been carried out with respect to the deposition time. As the deposition time is increased to 1 min, the Ag nano particles agglomerate to form clusters as shown in Fig1.b.It is evident that as the deposition time increases, the Ag nano particle size also increases and shows the linear relationship between the particle size and time [16]. SEM images in fig.…”

“…When Si wafer is dipped in the AgNO 3 and HF, a galvanic displacement reaction takes place which consists of two simultaneous processes [16]. Initially, Ag + ions attract electrons from Si wafer and convert to Ag nuclei.…”

“…Initially, Ag + ions attract electrons from Si wafer and convert to Ag nuclei. These Ag nuclei act as catalyst for the reduction of Ag + ions and Ag nuclei approaching the Si wafer attracts more electrons from Si because of its high electronegativity value [16]. This mechanism enables conversion of Ag nuclei to Ag particles.…”

Rapid Processing of Wafer-Scale Anti-Reflecting 3D Hierarchical Structures on Silicon and Its Templation

“…Thus a low activation energy is required to remove an atom from the (100) lattice; hence, (100) Si experiences faster etching with alkaline etchant solution than other surface orientations [12]. Nanotexturing on Si surface using metal nanoparticle assisted etching has also been reported [4,13,14,15,16]. Electroless etching using metal nanoparticles is a rather rapid and facile process.…”

<strong>Rapid and Facile Fabrication of Wafer Scale Silicon Hierarchical Structures with Broadband Ultra High Anti-Reflection Property</strong>

“…Electroless anisotropic etching can be performed when specific orientation (100) of crystalline Si is used that gives rise to pyramidal shaped microstructures. Electroless nanotexturing of Si wafers using metal assisted etching has also been reported which is a rapid process [4,10]. There are several reports where wet chemical anisotropic etching (in potassium hydroxide (KOH) bath) and metal assisted etching process have been combined to realize hierarchical structures on Silicon [2,3,11].…”