Germanium Nanowire Growth Below the Eutectic Temperature

TLDR

Nanowires are typically grown by the vapor‑liquid‑solid mechanism using a low‑melting eutectic catalyst, yet growth below the eutectic temperature has been observed, leaving the catalyst state controversial. In situ microscopy of the Ge/Au system revealed that nanowire growth below the eutectic temperature can proceed with either liquid or solid catalysts at the same temperature. The catalyst state depends on growth pressure and thermal history, likely due to kinetic enrichment of the eutectic alloy composition, and these findings may apply to other nanowire systems.

Abstract

Nanowires are conventionally assumed to grow via the vapor-liquid-solid process, in which material from the vapor is incorporated into the growing nanowire via a liquid catalyst, commonly a low–melting point eutectic alloy. However, nanowires have been observed to grow below the eutectic temperature, and the state of the catalyst remains controversial. Using in situ microscopy, we showed that, for the classic Ge/Au system, nanowire growth can occur below the eutectic temperature with either liquid or solid catalysts at the same temperature. We found, unexpectedly, that the catalyst state depends on the growth pressure and thermal history. We suggest that these phenomena may be due to kinetic enrichment of the eutectic alloy composition and expect these results to be relevant for other nanowire systems.