Facile generation of surface structures having opposite tone in metal-assisted chemical etching of Si: Pillars vs. holes

Easy control on etched surface structures, either pillars or holes, in metal-assisted chemical etching (MaCE) of Si is presented. Starting with Ag mesh film with holes, which is generated by Ag evaporation in combination with a colloidal monolayer mask, the usual MaCE process has led to the vertical arrays of Si pillars. On the other hand, O₂ reactive ion etching (RIE) on such Ag mesh film has led to sputtering and re-deposition of Ag on empty sites. During the following MaCE, the damaged Ag mesh spontaneously delaminates off the substrate and thus the etching with remaining Ag dot patterns results in holes array. Mechanistic studies of these etching behaviours have been performed and thus optimized, including the spontaneous mesh delamination. The obtained Si surfaces, either pillars or holes, were found to have comparable anti-reflection properties to other texturing approaches, which would be useful for photon management in applications such as photovoltaics, photoelectrochemical processes, etc.