Papers by Author: Osamu Takai

Abstract: Superlattice structure of SrTiO₃ and Nb-doped SrTiO₃ have been epitaxially grown on atomically flat surface of LaAlO₃ substrates by ion beam deposition method. Epitaxial superlattices were grown at 800 °C in the presence of partial oxygen pressure under optimizing growth conditions. The Nb-doped SrTiO₃ layers were varied from 2 to 15 unit cell thickness approximately, while SrTiO₃ layers are maintained at 15 unit cell thickness with 10 periods. The superlattices with various Nb-doped SrTiO₃ layer thicknesses were investigated using X-ray diffractometer (XRD) and atomic force microscope (AFM), in order to clearly understand structural properties and surface structure, which are significant for fabrication of the high quality superlattice structure.

Abstract: Plasma diagnosis was performed by means of optical emission spectroscopy in the plasma-enhanced chemical vapor deposition process for preparation of hydrocarbon-doped silicon oxide films. The chemical bonding states were characterized by a fourier-transform infrared spectrometer. Based on the results of the diagnosis in organosilane plasma and the chemical bonding states, a reaction model for the formation process of hydrocarbon-doped silicon oxide films was discussed. From the results of optical emission spectroscopy, we found that the oxygen atoms of methoxy groups in TMMOS molecules can be dissociated easily in the plasma and behave as a kind of oxidizing agent. Siloxane bondings in HMDSO, on the other hand, hardly expel oxygen atoms.