The Raman scattering measurement was recorded in the
backscattering geometry with an unpolarized light source, as
shown in Fig. 2. The most intense peak located at 520 nm comes
from the Si substrate. The peak at 437 cm−1 corresponds to a nonpolar
optical phonon E2 (high) of wurtzite ZnO, and it is an important
characteristic feature of the hexagonal phase ZnO. The peak at
582 cm−1 is attributed to the E1 (LO) mode of the hexagonal ZnO.
This peak is associated with the oxygen deficiency