A systematic study of tin-catalyzed vapor−liquid−solid (VLS) growth of silicon nanowires by plasma-enhanced chemical vapor deposition at temperatures ranging from 300 to 400 °C is presented. Wire structure, morphology, and growth rate are characterized as a function of process variables. The nanowires are observed to have a crystalline core with a polycrystalline shell due to simultaneous VLS axial growth and vapor−solid radial growth. Axial and radial growth rates are controllable through hydrogen dilution of the plasma which affects the concentration of silane radicals in the plasma. In addition, wire length is observed to saturate with increasing growth time. Post growth chemical analysis suggests this is due to etching and disappearance of tin seeds in the hydrogen plasma which occur in parallel with wire growth. This opens up the possibility of a unique in situ approach to fabricating metal-free nanowire arrays for device applications.

Ab initio calculations within the framework of hybrid density functional theory and the finite cluster approximation have been performed for the electronic and geometric structures of three different types of armchair germanium carbide nanotube, from (3, 3) to (11, 11). Full geometry and spin optimizations with unrestricted symmetry have been performed. Physically pertinent quantities of interest such as the cohesive energies, band gaps, radial buckling, density of states, dipole moments, and Mulliken charge distributions have been investigated in detail for all nanotubes. For type I nanotubes, the largest cohesive energy obtained is 4.092 eV/atom, whereas for type II and type III nanotubes, the values are 3.987 eV/atom and 3.968 eV/atom, respectively. For optimized type I nanotubes, Ge atoms moved toward the tube axis and C atoms moved in the opposite direction after relaxation, opposite to the trends observed in types II and III. The band gaps for type I nanotubes are larger than the bulk 3C-GeC gap, varying between 2.666 and 3.016 eV, while type II and type III nanotubes have significantly lower band gaps, with all nanotubes being semiconducting in nature. Mulliken charge analysis indicates primarily ionic behavior for type I GeC nanotubes and a mixed ionic with covalent behavior for the other two types. None of the tubes appear to be magnetic. Applications in the field of nano-optoelectronic devices, molecular electronics, and band gap engineering are envisioned for GeC nanotubes.

Using the Au-seeded vapor-liquid-solid technique, epitaxial single-crystal Si nanowires (NWs) can be grown laterally along Si(111) substrates that have been miscut toward [112¯]. The ratio of lateral-to-vertical NWs increases as the miscut angle increases and as disilane pressure and substrate temperature decrease. By exploiting these trends, conditions can be identified whereby all of the deposited Au seeds form lateral NWs. Growth is guided along the nanofaceted substrate via a mechanism that involves pinning of the trijunction at the liquid/solid interface of the growing nanowire.

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Free standing silica thin films with perpendicular ordered nanopores were obtained by electro-assisted self-assembly and subsequent detachment from PEDOT:PSS coated indium tin oxide (ITO) substrates.