With increase of seed layer thickness from 20 nm (Fig. 1A) to
320 nm (Fig. 1D), the diameter of nanorods increases from 30 nm to
72 nm and, at the same time, the density of nanorods decreases
from 213 mm2 to 169 mm2.
It is well known that the diameter of ZnO nanorods strongly
depends on the particle size of the seed layer [21]. As can be seen
in FE-SEM and AFM images, with increase of seed layer thickness,
the grain size and particle size of the seed layer increase and, since
the seed layer plays the role of a template for the nanorods, the
diameter of nanorods increases from 30 to 72 nm.