Density Functional Theory Study of the Silicene-like SiX and XSi3 (X = B, C, N, Al, P) Honeycomb Lattices: The Various Buckled Structures and Versatile Electronic Properties

Using the density functional theory calculations, we systematically investigate the structures and properties of silicene-like SiX and XSi3 (X = B, C, N, Al, P) hexagonal heterosheets. For the SiX systems, the SiP sheet favors a chairlike buckled structure akin to silicene, the SiB, SiN, and SiAl ones prefer the washboard-like buckling type, and the SiC sheet adopts the flat plane as graphene. The planarity is also favored in the XSi3 sheets with X = B, C, Al, while the rests with X = N and P prefer the chairlike buckled structures. The energetic stabilities and mechanical properties are also investigated for these SiX and XSi3 systems, and all the heterosheets are found to be stable. Unlike the semimetallic silicene, most of the SiX sheets are transformed to metals except for the SiC one with a wide band gap. For the XSi3 systems, they can be metals, semimetals, or narrow-band gap semiconductors depending on the X elements. The BSi3 and NSi3 sheets exhibit metallic behaviors, which behave like the p-type or n-type doping into silicene. On the other hand, the AlSi3 and PSi3 ones turn to semiconductors with narrow indirect band gaps, which are dominated by the Si–Si and Si–X bonding/antibonding states. Of particular interests, we find the CSi3 sheet maintains the zero-band gap semimetallicity of silicene, for which the pz orbitals of Si and C atoms contribute to the linear Dirac-like bands near the Fermi level. The dynamical stabilities of the CSi3, AlSi3, and PSi3 sheets are further examined by phonon calculations and ab initio molecular dynamics simulations, which confirm the robust stability of their free-standing states. Our studies demonstrate that the Si-related heterosheets have peculiar structures and properties, which have potential applications in the nanoelectronics and devices.