Structural Characterization of $La_{1-x}Sr_xCoO_3$ Thin Films Deposited by Pulsed Electron Deposition Method

The aim of the presented research was to investigate the influence of strontium dopant on the structure and composition of $La_{1-x}Sr_{x}CoO_3$ (x=0, 0.1, 0.2) perovskite thin films. Pure and Sr doped LaCoO₃ thin films were grown by pulsed electron deposition technique on crystalline epi-polished Si/MgO substrates. Numerous analytical techniques (scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction) were applied to characterize their phase/chemical composition, structure and surface morphology. X-ray diffraction analysis showed the presence of pure LaCoO₃ perovskite phase in the undoped thin film. For Sr doped thin films $La_{0.8}Sr_{0.2}CoO_3$ (x=0.2), $La_{0.9}Sr_{0.1}CoO_3$ (x=0.1) small contents of La₂ O₃ and LaSrCoO₄ phases were noticed. The crystallite sizes, calculated from the Williamson-Hall plots, were about 18 nm for all analyzed films. According to scanning electron microscopy/atomic force microscopy observations, obtained thin films were free from defects and cracks. Atomic force microscopy (tapping mode) analysis revealed the differences in the shape and quantity of surface crystallites for all thin films as a result of Sr doping and different deposition parameters. Atomic force microscopy technique also allowed measurement of roughness parameters for analyzed samples. X-ray photoelectron spectroscopy analyses of chemical states of elements of thin films showed that their chemical state was stable across the film thickness and even at the interface with the MgO substrate. X-ray photoelectron spectroscopy analysis also allowed to evaluate chemical states and atomic concentration of La, Co, and Sr elements within cross-sections of deposited thin films.