TEM/AFM study of the growth of La2−xSrxCuO4 thin films laser deposited on (100) SrTiO3 substrates

The growth characteristics of La2−xSrxCuO4 thin films of various thicknesses (10–150 nm), epitaxially grown by laser ablation on (100) SrTiO3 substrates, were analysed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). A periodic surface roughness with an important peak-valley amplitude (about 20% of the film thickness) was clearly observed in the films thicker than 25 nm. The period of the undulations did not depend on the deposited thickness. In contrast, AFM experiments performed on thinner films showed a perfect smoothness of the surface and a complete coverage of the substrate. These results were examined in connection with the fabrication of YBCO/LSCO(YBa2Cu3O7−δ/La2−xSrxCuO4) high Tc superconducting multilayer films.