The Process Of Oxide Heteroepitaxial Strain Study

Due to their versatile function, oxide thin films can be widely applied in the fields of microelectronics, optoelectronics and microelectronic mechanism systems. Thus the fabrication technology and growth control approach have been extensively investigated. Based on laser molecular beam epitaxy, the strain behavior and the corresponding control technology in oxides heteroepitaxial system, especially in ferroelectric thin films with perovskite structure, was systematically studied by using in situ reflected-high-energy-electron-diffraction (RHEED). Some original and meaningful results were obtained. Following aspects were included in this dissertation:The structure of thin films is analyzed by RHEED. RHEED is a powerful tool to monitor and analyze thin films growth dynamically. The growth modes (layer-by-layer mode, Stranski-Krastanov mode, 3D mode, texture, and growth modes transition) and strain relaxation behaviors (by measuring and calculating the spacing between chosen diffraction dots or streaks) can be tracked by RHEED from its diffraction patterns and intensity oscillations.The theoretical calculation and explanation of strain behavior during heteroepitaxy of oxides thin films: when the lattice mismatch is relative small (for example, BaTiO₃/SrTiO₃ with a lattice mismatch of 2.18%), the growth mode of thin films is layer-by-layer, and the critical thickness and strain relaxation can be calculated or estimated by Matthews-Blakeslee expressions; when the lattice mismatch is large (for example MgO/SrTiO₃ with lattice mismatch of 8%), the strain relaxation process can be explained by theory of coherent strained islands. For system with growth modes transition, different growth stages can be analyzed by different theory respectively, combined with RHEED.By using theoretical calculation and RHEED monitoring, the strain behavior in heteroepitaxy of ferroelectric oxides thin films was designed and controlled experimentally. (1) The Matthews-Blakeslee critical thickness within a wide range of lattice-mismatched systems was calculated. We found that the experimental critical...