Growth Mode of Superconducting La_2-xSr_xCu_l+yO₄ Thin Films on LaAIO₃ Substrate

La_2-xSr_xCu_l+yO₄(LSCO) thin films sputtered from a Cu-rich target on a LaAIO₃ substrate showed a columnar structure. The columnar grains penetrated the full thickness of the film, nucleating at the substrate surface defects. Transmission electron microscopy revealed two kinds of lattice images: one with a lattice spacing of 0.66 nm and the other with a spacing of 0.61 nm. The 0.66 nm spacing denotes a c-axis oriented LSCO film matrix. The 0.61 nm spacing has two categories: one with short white dashes, the phase of which is not yet identified, the other with no additional structure, which could correspond to the c-axis deviated LSCO.