It can be found that, with increase of seed layer thickness, the
crystallinity improves and the grain size increases, therefore the
nanorods will be better aligned.
Since in Wurtzite structure of hexagonal ZnO nanorods, side
planes are non-polar and stable; while top (Zn-terminated) and
bottom (O-terminated) planes are polar and quasi-stable; in the
hydrothermal growth process, polar planes can attract opposite
charges (Zn2þ or OH) from the solution and form nuclei. Liu et al.
[23] showed that, with increase of annealing temperature of the
seed layer and improvement of crystallinity, the growth rate of
nanorods will increase.