Decoupling Diameter and Pitch in Silicon Nanowire Arrays Made by Metal-Assisted Chemical Etching

The fabrication of well-separated, narrow, and relatively smooth silicon nanowires with good periodicity is demonstrated, using non-close-packed arrays of nanospheres with precisely controlled diameters, pitch, and roughness. Controlled reactive ion etching in an inductively coupled plasma reduces the self-assembled nanospheres to approximately a tenth of their original diameter, while retaining their surface smoothness and periodic placement. A titanium adhesion layer between the silicon substrate and gold film allows much thinner catalyst layers to be continuous, facilitating the film liftoff and formation of the perforated pattern without influencing catalyzed etching of silicon. Using these methods, a periodic array of silicon nanowires with a large pitch and small diameter (e.g., a 490 nm pitch and 55 nm diameter) is created, a combination not typically found in the open literature. This approach extends the types and quality of silicon nanostructures that can be fabricated using the combined nanosphere lithography and metal-assisted chemical etching techniques.