  We study the role of gold droplets in the initial stage of nanowire growth
via the vapor liquid solid method. Apart from serving as a collections center
for growth species, the gold droplets carry an additional crucial role that
necessarily precedes the nanowire emergence, that is, they assist the
nucleation of nanocraters with strongly faceted 111B side walls. Only once
these facets become sufficiently large and regular, the gold droplets start
nucleating and guiding the growth of nanowires. We show that this dual role of
the gold droplets can be detected and monitored by high energy electron
diffraction during growth. Moreover, gold induced formation of craters and the
onset of nanowires growth on the 111B facets inside the craters are confirmed
by the results of Monte Carlo simulations. The detailed insight into the growth
mechanism of inclined nanowires will help to engineer new and complex nanowire
based device architectures.
