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Open Access Nano Express

Catalytic activity of noble metals for metal-assisted chemical etching of silicon

Shinji Yae*, Yuma Morii, Naoki Fukumuro and Hitoshi Matsuda

Author Affiliations

Department of Materials Science and Chemistry, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo, 671-2280, Japan

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Nanoscale Research Letters 2012, 7:352  doi:10.1186/1556-276X-7-352

Published: 27 June 2012

Abstract

Metal-assisted chemical etching of silicon is an electroless method that can produce porous silicon by immersing metal-modified silicon in a hydrofluoric acid solution without electrical bias. We have been studying the metal-assisted hydrofluoric acid etching of silicon using dissolved oxygen as an oxidizing agent. Three major factors control the etching reaction and the porous silicon structure: photoillumination during etching, oxidizing agents, and metal particles. In this study, the influence of noble metal particles, silver, gold, platinum, and rhodium, on this etching is investigated under dark conditions: the absence of photogenerated charges in the silicon. The silicon dissolution is localized under the particles, and nanopores are formed whose diameters resemble the size of the metal nanoparticles. The etching rate of the silicon and the catalytic activity of the metals for the cathodic reduction of oxygen in the hydrofluoric acid solution increase in the order of silver, gold, platinum, and rhodium.

Keywords:
Porous silicon; Metal nanoparticles; Etching of semiconductor; Displacement deposition; Electroless plating; Electrochemical catalysts; Overpotential; Galvanic etching; Oxygen reduction; Anodic dissolution of silicon; 81.05.Rm; 82.45.Vp; 81.65.Cf