Structure of the defect layers in the oxide compound (${\mathrm{Ca}}_{0.3}$${\mathrm{Sr}}_{0.7}$${)}_{0.95}$${\mathrm{CuO}}_{2\mathrm{-}\mathit{z}}$

The structure of experimentally verified defect layers frequently present in the compound (${\mathrm{Ca}}_{0.3}$ ${\mathrm{Sr}}_{0.7}$ ${)}_{0.95}$ ${\mathrm{CuO}}_{2\mathrm{-}\mathit{z}}$ is investigated by means of dynamical contrast simulations. The results of this study reveal that, in the defect layers, the apical oxygen atoms may have a varying occupancy depending on the annealing conditions. This specific feature of the structure results in hole-doped as well as electron-doped superconductivity occurring in the oxidized and in the reduced specimen (${\mathrm{Ca}}_{0.3}$ ${\mathrm{Sr}}_{0.7}$ ${)}_{0.95}$ ${\mathrm{CuO}}_{2\mathrm{-}\mathit{z}}$, respectively.