OBSERVATION OF LOCAL OXYGEN DISPLACEMENTS IN CUO2 PLANES INDUCED BY AMISFIT STRAIN IN HETEROEPITAXIALLY GROWN INFINITE-LAYER-STRUCTURE CA1-XSRXCUO2 FILMS

?he role of various intergrowth defects acting as charge reservoirs in infinite-layer-structure Ca1-xSrxCuO2 films is widely discussed, whil e internal structural properties of the CuO2 planes that are important in acquiring the charge have received significantly less attention. W e present experimental evidence based on reflection high-energy electr on diffraction and extended x-ray-absorption fine structure data that the epitaxial misfit strain in infinite-layer Ca1-xSrxCuO2 films grown by molecular beam epitaxy tan induce oxygen displacements in the CuO2 planes resulting in a buckling of the CuO2 sheets. The displacements are explained by the relief of strain from the CuO2 planes in infinite -layer films grown under compressive stress. For films that undergo te nsile stress the CuO2 sheets remain planar. The results show that obse rved structural properties of CuO2 planes have a large impact on charg e-carrier density and can considerably promote the ability of the CuO2 planes to be optimally charged.