Center for Functional Nanomaterials Seminar

Metal-assisted chemical etching is a relatively new top-down approach allowing a highly controlled and precise fabrication of Si and Si/Ge superlattice nanowires. It is a simple method with the ability to tailor diverse nanowire parameters like diameter, length, density, orientation, doping level, doping type, and morphology. Nanowire diameters in the range of several microns down to 10 nm can be obtained.
In a typical metal-assisted chemical etching procedure a Si substrate is covered by a lithographic noble metal film and etched in a solution containing HF and an oxidant (typically H2O2). In general, the function of the metal is to catalyze the reduction of H2O2, which delivers electronic holes necessary for the oxidation and the subsequent dissolution of the Si oxide by HF. However, the details of the etching process, especially the mass and charge transport of reactants and byproducts, are still not well understood.
In the first part of the talk, several models of metal-assisted etching using a contiguous metal film as a catalyst will be presented and discussed . Their validity will be assessed by performing several different well-controlled experiments. The results lead to better understanding of the etching mechanism on a microscopic scale and thus to a better control of the fabrication process. In the second part of the talk several applications of metal-assisted chemical etching will be presented and main technical difficulties discussed.