Figure 1.

MacEtch mechanism in solution of HF and H₂O₂. (a) The metal catalyst deposited on a Si <100> substrate decomposes H₂O₂ with consequent injection of holes (+) into the semiconductor. (b) Si consumes the positive carriers Si, it is readily oxidized by HF and forms silicon fluoride, the process continues and the catalyst progressively sinks into Si along the <100> direction, transferring the nanostructure pattern to the Si (formation of nanopillars in this case). Images are cross-section Scanning Electron Microscopy (SEM) of nano-patterned Pt on Si (a) after few seconds of MacEtch in solution of HF and H₂O₂.