Formation Mechanism of Heavily Doped Silicon Mesopores Induced by Pt Nanoparticle-Assisted Chemical Etching

Metal-assisted chemical etching (MACE) is a facile process to produce mesoporous silicon compared with conventional stain etching and electrochemical etching. However, less work focuses on the MACE process with Pt as a catalyst. In this work, Pt nanoparticle (PtNP)-assisted chemical etching in heavily doped p-type silicon (0.001-0.002 Omega cm) is investigated. Scanning electron microscope and transmission electron microscopy methodologies are used to observe the morphologies of mesopores obtained by changing the etching solution composition. An interesting etching behavior is found that the mesopores are uniformly generated in silicon firstly and then partially dissolved. In addition, the size of the mesopores decreases with the concentration of hydrofluoric acid, similar to the phenomena revealed in electrochemical etching. An etching mechanism is proposed on the basis of the dissolution and redeposition of PtNPs. The former is responsible for the generation of electric field, which is essential for the formation of the mesopores; whereas the latter contributes to the dissolution of the mesopores. These findings are beneficial to deep understanding of the MACE process.