The deep band emission at 490 nm is reported
due to singly ionized oxygen vacancy resulted
from the recombination of photo-generated hole with
the singly ionized charge state of this defect[20]. The
optical phonon modes of grown ZnO nanorods were
analyzed using Raman scattering and a typical Raman
spectrum is presented in Fig. 8. A sharp peak
observed at 437 cm−1 belongs to the Raman active
optical-phonon E2 mode of wurtzite hexagonal ZnO
crystal[21].