Spontaneous formation of Si nanocones vertically aligned to Si wafers

A simple, practical method was developed to automatically align single crystalline Si nanocones (SiNCs) vertical to a Si substrate. Double heteroepitaxial structure of SiCo Si2 on a Si (100) substrate was prepared by sputtering, and Si was then deposited on the surface via chemical vapor deposition with Si H2 Cl2 H2 reaction gas. When Si was deposited at 900 °C, SiNCs were fabricated vertical to the substrate, had a tip curvature of about 100 nm, and had a number density of (0.9-35) × 108 m2. A Co Si2 nanocrystal was clearly visible on the tip of each SiNC. These Co Si2 nanocrystals were formed by agglomeration of the SiCo Si2 layer, and catalyzed the Si growth during chemical vapor deposition. In conclusion, the alignment of the fabricated SiNCs could be controlled by utilizing agglomeration in the SiCo Si2 Si double heteroepitaxial structure.