Helical nanoholes bored in silicon by wet chemical etching using platinum nanoparticles as catalyst

Helical as well as cylindrical holes with diameters ranging from 20 to 200 nm were bored in silicon by wet chemical etching in a solution containing HF and H2O2 using Pt nanoparticles deposited on the silicon surface before the etching process as a catalyst. In a solution containing HF at a low concentration, cylindrical holes grew preferentially in the < 100 > direction at the centers of cone-shaped concavities filled with microporous silicon. On the other hand, in a solution containing HF at a high concentration, helical holes grew in various directions without forming a thick microporous silicon layer. (c) 2005 The Electrochemical Society.