Phonon Raman scattering study of K2NiF4 type oxide superconductors

La (P-1) and epical oxygen (P-2) vibrations along the c-axis, which are A(1g)-symmetry in the tetragonal phase (I4/mmm), have been systematically investigated for K2NiF4-type oxide superconductors; La2CuO4+delta (delta=0; 0.014: 0.063); La1.86Sr0.15CuO4, and Sr2RuO4. For La2CuO4+delta, with increasing of the excess oxygen concentration (delta), the intensity of P-2 decreases exponentially as a function of delta at room temperature. This decrease can he understood by the shielding effect due to the doped carriers along the c-axis. With decreasing temperature, the intensity of P-2 increases for La2CuO4.063 and La1.85Sr0.15CuO4 at low temperature, while La2CuO4 and Sr2RuO4 do not show such anomaly. This might be explained by the decrease of the shielding effect due to the charge confinement along the c-axis. The appearance of the excess oxygen vibration along the c-axis shows that the transition at about 250 K is due to the freezing of the itineracy of the excess oxygen for La2CuO4.063.