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.