Oxide shell assisted vapor-liquid-solid growth of periodic composite nanowires-a case of Si/Sn

In the conventional vapor-liquid-solid (VLS) growth process, the wires or whiskers grown from the liquid catalyst droplets are always in the solid state. Here, we report the synthesis of a silicon-based periodic nanowire structure using a periodic volume-changing Sn particle as catalyst. Contrary to the common VLS process, the nanostructure growth was instead governed by a catalyst head consisting of a mixture of solid and liquid, and liquid Sn segments periodically appeared in Si nanowires during the growth process. The liquid Sn segments catalyzed the growth of secondary or branching nanowires from the primary nanowires. The result reveals clearly that the unusual growth is governed by the dual action of VLS and oxide-assisted growth (OAG). It further suggests a new pathway to rational design and synthesis of periodic composite nanostructures by taking advantage of both VLS and OAG processes. © 2007 American Chemical Society.