Galvanic deposition of Pt clusters on silicon: effect of HF concentration and application as catalyst for silicon nanowire growth.

We report on the galvanic deposition of Pt on Si from solutions containing PtCl(2) and different concentrations of HF. The results show that for low [HF]/[Pt] ratios (<or=26), only a thin layer of PtSi is formed. The deposition rate of Pt increases with [HF] in the plating solution, up to [HF]/[Pt] approximately 530; after this ratio, the morphology of the Pt film changes: larger clusters are formed, which cover the Si substrate less densely. Detailed atomic force microscopy and X-ray photoelectron spectroscopy analyses show that the deposited Pt layers do not completely cover the Si substrate. The Pt and PtSi films formed are able to catalyze the formation of Si nanowires (Si NWs) arrays formed via vapor-liquid-solid (VLS) process. By changing the immersion time in the Pt plating solution, Si NWs arrays with different density, diameter, and orientation are obtained.