Fig. 2

Schematic images of the surface of the SiNSs showing the adsorption process. Gray bonds represent the back bonds of the SiNSs, and blue bonds represent the bonding of the surface atoms. a The adsorption process on the (111) surface. The atoms on site A have bonds with the surface atoms. The atoms on site B bond with atoms on site A. In a diffusion-limited environment, it is difficult for atoms on site B to bond with atoms on site A and could not form the (111) layer because of the diffusion of atoms on site A. b On the (110) surface, atoms on site A act as a step site. Therefore, atoms adsorbed on site B have two bonds. c Projection view towards the [112] direction shows the diffusion of adsorbed atoms on the (111) surface to the (110) surface