Formation mechanism of nanocatalysts for the growth of silicon nanowires on a hydrogen-terminated Si {111} surface template.

We have observed the formation process of nanocatalysts that act for the growth of Si nanowires by means of UHV scanning tunneling microscopy. Gold-silicon nanocatalysts that we have examined were thought to form on a hydrogen (H)-terminated [111] silicon surface and to expel Si nanowires of extremely high aspect ratio via the vapor-liquid-solid mechanism. We have observed that a nanocatalyst, that is, a droplet of melted gold-silicon alloy of about 5 nm in diameter, is actually formed in a pit on a H-terminated surface in the narrow temperature range around 500°C. We have concluded that, in this specific temperature range, nanocatalysts can be melted, remain mutually isolated, absorb silicon effectively, and expel Si nanowires. Based on the result, we have proposed a method of making a thin template, which facilitates to decide the nucleation sites and the sizes of nanocatalysts, resulting in the precise control of those of Si nanowires. [ABSTRACT FROM AUTHOR]