Twinned Si nanowires grown by high temperature annealing of Au/Si system in vacuum

• Colloidal Au nanoparticles are deposited on SiO2 surface.
• Vacuum annealing processes on the Au nanoparticles/SiO2 systems are performed.
• The growth of nanowires from the Au nanoparticles is observed.
• In the vacuum-annealing condition, a twinned-faceting of the nanowires is observed.
• A linear relation between the twins size and nanowires radius is found and discussed.

Periodically twinned Si nanowires were fabricated on Si surface by high-temperature annealing, in vacuum, of deposited colloidal Au nanoparticles. While performing the annealing process in a gas carrier with trace amounts of oxygen almost-cylindrical silica nanowires are obtained thanks to the stabilizing effect of the oxygen, faceted nanowires are obtained in vacuum condition. In this last case, nanowires with diameter in the 70–150 nm range and length of some microns are obtained. They present an arrangement of periodically twinned segments with a rather uniform thickness along the entire growth length. A minimum surface energy and strain energy argument is used to explain the formation of periodic twins in the Si nanowires. The thickness of the periodic twinned segments is found to be linearly proportional to the nanowire diameter, and a constant volume model is used to explain the relation. By the fit of the experimental data, in particular, an estimation of the twin energy formation is obtained.

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