We deposit fine metal particles on silicon (Si) by a displacement reaction, which is the immersion of Si wafers into a metal-salt solution containing hydrofluoric acid, that consists of a local cathodic reduction of metal ions and a local anodic dissolution of Si. In this study, the displacement deposition of silver (Ag) nanoparticles on the Si(111) surface with an atomic step-terrace structure is investigated by atomic force microscopy. Ag particles are uniformly deposited on the Si surface without influence of the step-terrace structure. The particle density of the deposited Ag decreases and then increases with immersion times between 1 and 15 s. The step-terrace structure disappears and nanoholes are formed by an immersion time of 15 s. We propose a model of Ag particle density and Si surface changes with time.

Fine metal particles can be formed on Si using electroless displacement deposition, by which Si wafers are simply immersed into a metalsalt solution containing HF. Depending on the kind of metal and the surface conditions of Si substrates, the particle density of the deposited metal varies widely. Especially, the Pt particle density greatly changes according to Si surface conditions. This study investigated the influence of Ar-plasma etching of Si on the Pt particle density. Single-crystalline n-Si (100) wafers were etched by Ar plasma using a radiofrequency glow discharge spectrometer. An amorphous Si layer was formed on etched Si surfaces. By immersing Ar-plasma-etched Si wafers in a H 2 PtCl 6 solution containing HF, Pt particles with particle density four hundred times higher than that for non-etched Si wafers were deposited. The Pt particle density was decreased by removing the amorphous layer and by chemical etching of the single-crystalline Si wafer. Results show that the influence of Ar-plasma-etching extended at least 0.5 μm to the interior of single-crystalline Si beneath the amorphous layer.