Galvanic porous silicon formation without external contacts

Porous silicon is usually formed under anodic polarization in an electroche mical cell. In this paper, a technique is described for forming porous sili con without using an external current or voltage source. By connecting an i nert metal electrode to a silicon sample, both immersed in a HF solution, a galvanic cell is formed. Reduction of oxygen at the inert electrode result s in the etching of Si at the silicon/electrolyte interface. Porous silicon is formed at a rate which is dependent on the cell current. The formation rate may be enhanced by adding oxidizing agents to the solution. Galvanic e tching for forming porous Si isa promising alternative for stain etching si nce it gives more uniform and reproducible results. (C) 1999 Elsevier Scien ce S.A. All rights reserved.