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Using the density functional theory calculations, we systematically investigate the structures and properties of silicenelike SiX and XSi 3 (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 washboardlike buckling type, and the SiC sheet adopts the flat plane as graphene. The planarity is also favored in the XSi 3 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 XSi 3 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 XSi 3 systems, they can be metals, semimetals, or narrow-band gap semiconductors depending on the X elements. The BSi 3 and NSi 3 sheets exhibit metallic behaviors, which behave like the p-type or n-type doping into silicene. On the other hand, the AlSi 3 and PSi 3 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 CSi 3 sheet maintains the zero-band gap semimetallicity of silicene, for which the p z orbitals of Si and C atoms contribute to the linear Dirac-like bands near the Fermi level. The dynamical stabilities of the CSi 3 , AlSi 3 , and PSi 3 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.

Using first principles calculations, we investigate the electronic properties of silicon nanoribbons (SiNRs). We find that the armchair SiNRs can be metals or semiconductors depending on width. For the zigzag SiNRs, the antiferromagnetic semiconducting state is the most stable one. Under transverse electric field, the zigzag SiNRs become half-metals. These results show that SiNRs have both rich electronic and magnetic properties with potential applications in silicon-based electronic and spintronic nanodevices.

Silicene is the graphene-like silicon nanosheet, which has been synthesized very recently [B. Lalmi, H. Oughaddou, H. Enriquez, A. Kara, S. Vizzini, B. Ealet, and B. Aufray, Appl. Phys. Lett. 97, 223109 (2010)]. Using first-principles calculations, we systematically investigate the structures and properties of fluorinated and hydrogenated silicene, the silicon analogues of graphane. Different from the carbon-counterpart, the fluorination prefers the conformation with a zigzag-line buckling, while the hydrogenation keeps the chair conformation similar to graphane. A direct band gap is opened in the silicene fluoride, and the gap values can be continuously modulated by the strain. While for the hydride, a strain-induced indirect-to-direct band gap transition is found.