Research On The Growth And Interface Control Of Ferroelectric Oxide Films

Owing to their versatile function, ferroelectric thin films with perovskite structure can be applied in the fields of microelectrics, optoelectronics and microelectric mechanism sysmtem, thus the fabrication technique and growth control have been extensively studied. Aiming at the mechanism of epitaxial ferroelectric and buffer layer during the growth in the laser molecular beam epitaxy, this dissertation had touched the following aspects:Through systematically research on the homoepitaxial growth of SrTiO₃, the typical perovskite oxide, it was revealed that the deposition rate, surface morphology and growth mode of the films could be controlled by experimental parameters. The deposition rate is direct proportion to the laser repetition, and shows linear relation in the range of appropriate density of laser energy. In the phase diagram of the growth mode, the film is inclined to grow layer-by-layer at higher temperature or lower deposition rate, and grow by island mode even can not crystallize at lower temperature or higher rate, thus at very low temperature (～300℃) epitaxial films could be obtained at a low deposition rate. Furthermore, the surface recovery during the annealing has been in-situ monitored by reflection high-energy electron diffraction (RHEEED). From the characteristics relaxation times as a function of substrate temperature, the surface relaxation occurred with activity energy for diffusion of ⁰.3eV, which was very close to the value of ionic compound, thus was argued to be attributed to the diffusion of charge-neutral SrTiO₃ units. Annealing experiments also showed that the surface recovery was weakened with the increase of film thickness, and this would result in the change of RHEED oscillation period during later deposition.By analyzing RHEED patterns during the homoepitaxial growth of SrTiO₃, the oscillation behavior of in-plane lattice constant and full-width at half maximum (FWHM) of diffraction streaks was displayed to have the same period as RHEED intensity oscillation, the former is due to the interface between the annealed reconstruction surface and growing film, and the origin of the latter is relation to the relaxation of 2D islands by their edges. In addition, the phase shift of RHEED intensity oscillation was observed, due to plasma influence on incident electron beam.For the heteroepitaxial systems with small mismatch (<5%), cube-on-cube...