We have developed an unifying tight-binding Hamiltonian that can account for the electronic properties of recently proposed Si-based nanostructures, namely, Si graphene-like sheets and Si nanotubes. We considered the $sp^3s^*$ and $sp^{3}$ models up to first- and second-nearest neighbors, respectively. Our results show that the Si graphene-like sheets considered here are metals or zero-gap semiconductors, and that the corresponding Si nanotubes follow the so-called Hamada's rule [Phys. Rev. Lett. {\bf 68}, 1579 1992]. Comparison to a recent {\it ab initio} calculation is made.Comment: 12 pages, 6 Figure

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The structural and electronic properties of the hydrides of silicene and germanene have been studied using ab initio calculations. The trend for the M–H (M=C, Si, and Ge) bond lengths, and corresponding bond energies, is consistent with the atomic size trend, and comparable to those of MH4 hydrides. Band structures were also obtained for the buckled configuration, which is the stable form for both silicene and germanene. Upon hydrogenation, both silicane (indirect gap) and germanane (direct gap) are semiconducting.

Wurtzite (w-) ZnS nanowires with nearly square cross sections have been grown by pulsed laser vaporization of a (ZnS)0.9Au0.1 target in a flow of Ar 5%H2. Growth proceeds by the vapor−liquid−solid mechanism. Raman scattering from the ZnS nanowires in air at room temperature reveals a strong first-order longitudinal optic (LO) phonon (346 cm-1) and two transverse optic (TO) phonons (269 and 282 cm-1), as well as several second-order features. Peak assignments based on bulk ZnS can be made for all the first- and second-order features, except for one band located between the LO and TO bands. This additional Raman band is observed at 335 cm-1 in air, and downshifts to 328 cm-1 in dichloromethane (ε m = 2.0) and to 326 cm-1 in aniline (ε m = 2.56). This band is therefore assigned to surface optic (SO) phonons. The position of the SO band is consistent with a dielectric continuum model for rectangular cross section wires. A symmetry breaking mechanism which may activate the SO mode is also discussed.