Papers by Author: Jiechao Jiang

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Authors: Y. Fang, V.R. Sakhalkar, J. He, H.Q. Jiang, Jiechao Jiang, Efstathios I. Meletis
Abstract: Synthesis of high quality epitaxial LaMnO3 and (La,Sr)MnO3 films on large areas is highly desirable. Recently, we have deposited LaMnO3 and (La,Sr)MnO3 films on the MgO (001) and LaAlO3 (001) substrates using RF magnetron sputtering. Highly epitaxial quality thin films have been successfully obtained at 750 °C by manipulating processing parameters as characterized by X-ray diffraction, electron diffraction and HRTEM. The epitaxial LaMnO3 and (La,Sr)MnO3 thin films have either a tetragonal or orthorhombic crystal structure depending on the film (target) composition and substrate type. The (La,Sr)MnO3 films were found to have an orthorhombic crystal structure when deposited on LaAlO3 substrate and a tetragonal structure when deposited on MgO substrate; whereas LaMnO3 films have a tetragonal structure when deposited on LaAlO3 substrate and an orthorhombic crystal structure when deposited on MgO substrate. The orthorhombic structures of the (La,Sr)MnO3 film on LaAlO3 and LaMnO3 on MgO are oriented with their c-axis on the film plane. Magnetic studies show that the epitaxial films have higher phase transition temperature than the corresponding bulk material and to those obtained using pulse laser deposition. Successful synthesis of highly epitaxial quality films by RF magnetron sputtering over a larger area can result in reduced cost for fabricating and processing epitaxial thin films.
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Authors: Jiechao Jiang, Efstathios I. Meletis, Z. Yuan, Jian Liu, Jenny Weaver, Chong Lin Chen, B. Lin, V. Giurgiutiu, R.Y. Guo, A.S. Bhalla, D. Liu, K.W. White
Abstract: We report the fabrication of the orientation preferred structures in BaTiO3 thin films on Ni substrates using pulsed laser deposition. Transmission electron microscopy studies showed that the films consist of crystalline structures of tetragonal BaTiO3. More than 60% of BaTiO3 grains in the films exhibit nearly the same crystallographic orientation with their a-axis lying in the film plane and the [011] direction parallel to the growth direction. Such orientation preferred structures were grown on a Ni nanocrystalline buffer layer. This result demonstrated the possibility of approximating an oriented single crystalline ceramic oxide structures on metallic substrates.
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Authors: Jiechao Jiang, J. He, Efstathios I. Meletis, Jian Liu, Z. Yuan, Chong Lin Chen
Abstract: Two-dimensional in-plane interface structures of highly epitaxial perovskite (La,Ca)MnO3 (LCMO) and (Pb,Sr)TiO3 (PSTO) thin films on salt-rock type MgO substrate were studied using Transmission Electron Microscopy (TEM). Cross-section TEM studies revealed that both LCMO and PSTO films are good single crystal quality and have atomic sharp interface with respect to the MgO substrate with -6.4% and -6.2% lattice mismatch, respectively. Electron Diffraction Patterns (EDPs) of plan-view LCMO/MgO and PSTO/MgO interfaces exhibit double diffraction spots. An analytical approach was employed using double diffraction to study the two-dimensional in-plane interfaces of perovskite structure films on the salt-rock type substrate. The lattice mismatch near the interface regions was determined using EDPs of the plan-view interfaces and found to be -8.0% for LCMO/MgO and -7.14% for PSTO. Both latter values are larger than those obtained using cross-section TEM. Studies of the sharpness of double diffraction spots and plan-view high resolution (HR) TEM brought a conclusion that the PSTO film is well commensurate with the MgO substrate over large areas, whereas LCMO film is only locally commensurate with the substrate. These studies provide additional evidence to our previous observations that plan-view TEM of the interface is able to provide critical and valuable information that is lacking from the cross-section TEM analysis.
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