The Raman study has been performed on YBa
2Cu
3O
x=7−δ (YBCO)/MgO thin films. Two modes at 232 and 596 cm
−1 are exhibited in a film with continuous oxygen depletion. The modes are related to in-phase stretch [] and out-of-phase stretch [←OCuo→] along the b-direction, where O(1) and o(1) are full and deficient oxygen, respectively. They are interpreted thoroughly by other publications.
Oxidized Cu films show the 630-cm−1 phonon that is consistent with a mode in YBCO. This result allows us to consider the phonon as a defect mode induced from CuO molecules which are nonstoichiometric in YBCO crystals.