  New insights into controlling nanowire merging phenomena are demonstrated in
growth of thin ZnO nanowires using monodispersed Au colloidal nanoparticles as
catalyst. Both nanowire diameter and density were found to be strongly
dependent on the density of Au nanoparticles. Structural analysis and spectral
cathodoluminescence imaging of the c-plane nanowire cross-sections reveal that
thin isolated nanowires growing from the Au nanoparticles begin to merge and
coalesce with neighbouring nanowires to form larger nanowires when their
separation reaches a threshold distance. Green luminescence, which is
originated from the remnants of constituent nanowires before merging, is
detected at the core of fused nanowires. The distribution of nanowire diameters
and green emission were found to be strongly dependent on the density of the Au
nanoparticles. The merging phenomenon is attributed to electrostatic
interactions between nanowire c-facets during growth and well-described by a
cantilever bending model.
