Preparation and properties of ferroelectric/semiconductor hybrid-lattice inrefaces

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The object of the present study is to make oxide (ferroelectrics) / semiconductor hybrid-lattice interfaces and to clarify the electric and/or optic properties of heterostructures having the above interfaces. The results obtained were summarized as follows.1) Strontium oxide thin films were epitaxially grown on a hydrogen-terminated Si (111) surface by a molecular beam exitaxy (MBE) process. The hydrogen termination process was essentially important to obtain an oxide/Si hybrid-lattice interface.2) A full automatic deposition control system was developed for MBE process to realize an atomic-layr epitaxy with the resolution below mono-layr. Artificial superlattices and artificially modulated structures of strontium titanate (STO) and barium titanate (BTO) were prepared by this system. Clean interfaces with a perfect lattice matching (hybrid-lattice interface) were obtained. The ferroelectric properties of the modulated structures were found to be different from that of a simple solid solution of STO and BTO.3) A ferroelectric lithium tantalate/semi-conductive zinc oxide heterostructure was prepared on a sapphire substrate and its optical property was measured by a spectroscopic ellipsometer. Software for operation and analysis of ellipsometry was newly developed to solve various problems existing in the ellipsometry of transparent films. The optical constants determined by this system was well consistent with the reported data for bulk specimens.