Density Functional Theory Study of Metallic Silicon (111) Plane Structures.

The band structure on the surface might be influenced by the abruptly ended periodic structure and change the physical properties of the semiconductor. By using the density functional theory, this research also demonstrates that the Si unit cell has the calculated room-temperature electrical conductivity as 4.01 × 10 -6 (Ω -1 cm -1 ), similar to the experimental result. Thus, the Si(111) plane structures are calculated, and we found out that the one-layer and two-layer plane structures have the theoretical room-temperature electrical conductivities as 129.68 (Ω -1 cm -1 ) and 547.80 (Ω -1 cm -1 ), respectively. In addition, the results reveal that the conduction band and valance band of the Si(111) one-layer and two-layer structures will connect on the ⟨111⟩ direction, mainly contributed by Si 3p orbitals. Thus, the band structure at the ⟨111⟩ direction on the Si(111) surface has variation and increases the electrical conductivity to 7 to 8 orders compared to the intrinsic Si and offers new surface science and surface engineering concepts for future applications.