Textured thin films grown at room temperature by laser ablation

Thin films of SrFe₁₂O₁₉, BaFe₁₂O₁₉, Pb_0.76La_{0.16 0.08}Zr_0.53Ti_0.47O₃and Sr_0.3Ba_0.7Nb₂O₆ were grown on monocrystalline silicon substrates by pulsed laser deposition using a 20-ns Nd:YAG laser (1064 nm). The deposited thin films were analyzed by X-ray diffraction in the grazing incidence configuration. The analysis showed evidence of textured growth even though the films were grown at room temperature. Emission spectroscopy was used to establish the time of flight of the species within the plasma plume. Velocities of the order of 10⁶ cm/s were obtained. The high kinetic energy of the species is thought to be responsible for the film texture, as it is released in the substrate–film system, favoring a preferential growth. For all the ablated ceramics, singly ionized species were shown to expand at higher velocities than neutrals. For ions, no consistency in the mass–speed relation was obtained, suggesting both the presence of electric fields during the plasma formation and an evaporation of the target that depends on the vapor pressure of the elements. In this way species that are firstly evaporated will be attracted strongly by fast electrons, allowing heavy ions to acquire higher velocities than lighter ones. PACS 81.15.Fg; 52.38.Mf; 68.55.Jk; 52.38.Kd; 52.70.Kz