Maskless Spatioselective Functionalization of Silicon Nanowires

Spatioselective functionalization of silicon nanowires was achieved without using a masking material. The designed process combines metal‐assisted chemical etching (MACE) to fabricate silicon nanowires and hydrosilylation to form molecular monolayers. After MACE, a monolayer was formed on the exposed nanowire surfaces. A second MACE step was expected to elongate the nanowires, thus creating two different segments. When monolayers of 1‐undecene or 1‐tetradecyne were formed on the upper segment, however, the second MACE step did not extend the nanowires. In contrast, nanowires functionalized with 1,8‐nonadiyne were elongated, but at an approximately 8 times slower etching rate. The elongation resulted in a contrast difference in high‐resolution scanning electron microscopy (HR‐SEM) images, which indicated the formation of nanowires that were covered with a monolayer only at the top parts. Click chemistry was successfully used for secondary functionalization of the monolayer with azide‐functionalized nanoparticles. The spatioselective presence of 1,8‐nonadiyne gave a threefold higher particle density on the upper segment functionalized with 1,8‐nonadiyne than on the lower segment without monolayer. These results indicate the successful spatioselective functionalization of silicon nanowires fabricated by MACE.