Investigation of Ag-assisted chemical etching on (100) and (111) contiguous silicon surfaces

Electroless silver deposition (for 1-100s) has been simultaneously performed on (100) and (111) planes of macro and micro patterned silicon, fabricated using optical lithography and anisotropic etching with alkaline solution. Metal clusters formation occurs preferentially on the upper edge region separating the two main planes. Their density and mean size are higher on the (100) plane. Similar experiments performed on same patterned samples but with the surface amorphized by ion implantation elucidated the role played by the preferential mass transport caused by the pattern geometry. For the micro-sized pyramidal holes, the non uniform surface distribution of metal clusters is enhanced. The metal deposition occurs mainly on the (100) top strips surrounding the pyramids. The subsequent preferential oxidation of silicon under the metallic clusters gives rise to nanowires of (100) and (111) orientation in the macro and to nanopillars in the micro patterns respectively. Nanowire's tips are preferentially sites for metal deposition as shown after re-immersion in the plating solution. Samples with contiguous one dimensional nanostructures of different orientation could be used for the study of transport properties' anisotropy. The formation of metal tips on top of the nanostructures might be of relevance in the field of metal-semiconductor contacts.