Papers by Author: Naoki Wakiya

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Authors: Takanori Kiguchi, Naoki Wakiya, Kazuo Shinozaki, Nobuyasu Mizutani
Authors: Takanori Kiguchi, Naoki Wakiya, Kazuo Shinozaki, Nobuyasu Mizutani
Authors: Ryoichi Saotome, Naoki Wakiya, Takanori Kiguchi, Jeffrey S. Cross, Osamu Sakurai, Kazuo Shinozaki
Abstract: Highly oriented and polycrystalline Gd2O3 doped CeO2 thin films were prepared on α-Al2O3(0001) substrates by chemical vapor deposition, using Ce(C5H4C2H5)3 and Gd(C5H4C2H5)3 as precursors. The compositions of the films were controlled by optimizing the vaporization pressure of Gd precursor under the constant vaporization condition of Ce precursor. In-plane electrical conductivities of the films at various temperatures and oxygen partial pressures were evaluated by electrochemical impedance spectroscopy measurements. The activation energy of the film was determined as 0.94 eV, which is comparable with that of pulsed laser deposited films.
Authors: Shigeki Sawamura, Naonori Sakamoto, De Sheng Fu, Kazuo Shinozaki, Hisao Suzuki, Naoki Wakiya
Abstract: Thermal stability of bottom electrode thin films (La0.5Sr0.5)CoO3 (LSCO) and (La0.6Sr0.4)MnO3 (LSMO) were investigated. The crystallization and surface morphology of the heterostructure were characterized using x-ray diffraction and atomic force microscopy. Resistivity of the LSCO thin film was 25 cm. However, the resistivity of LSCO thin film increases sharply with annealing temperature. The LSMO thin film has high resistivity (100 mcm). The film does not decompose after thermal processing at 900 °C. To confirm thermal stability, we examined the effect of post annealing at various temperatures on the morphology and resistivity. Results showed that LSMO has higher thermal stability than that of LSCO.
Authors: Naoki Wakiya, Akinori Higuchi, Haruki Ryoken, Hajime Haneda, Keiichi Fukunaga, Noriyoshi Shibata, Toshimasa Suzuki, Yuji Nishi, Kazuo Shinozaki, Nobuyasu Mizutani
Abstract: Diffusion behavior at the interface of (001)-epitaxially grown (Ba,Sr)TiO3(BST)/electrode/buffer layer/Si thin films was examined by use of secondary ion-microprobe mass spectrometer (SIMS) and transmission electron microscope (TEM) attached with energy dispersive X-ray fluorescence spectrometer (EDX). As the (001)-epitaxially grown film, following three kinds of structure was grown; (1)BST/(La,Sr)CoO3(LSCO)/CeO2/yttria-stabilized zirconia(YSZ)/Si, (2)BST/PLD-deposited Pt/SrTiO3(ST)/LSCO/CeO2/YSZ/Si and (3)BST/sputter-deposited Pt/ST/LSCO/CeO2/YSZ/Si. For sample (1), uphill diffusion of Sr and Ti was observed at the interface of YSZ and SiO2. Diffusion of Co into CeO2 layer was also detected. These tendencies of diffusion were also observed for samples (2) and (3). In addition to these tendencies, apparent uphill diffusion of Co at the Pt layer was observed for sample (2). However, this diffusion was not observed for sample (3). It was also observed that oxygen diffusion was prevented for sputter-deposited Pt. On the other hand, oxygen diffusion was observed for PLD-deposited Pt.
Authors: Ji Won Moon, Shogo Tazawa, Naoki Wakiya, Takanori Kiguchi, Youhei Ishida, Nobuyasu Mizutani, Kazuo Shinozaki
Abstract: Pb(Zr, Ti)O3 thin films were successfully prepared on (111)Pt/IrO2/SiO2/(100)Si substrates using SrTiO3 seeds at 290 oC by RF inductive heating type and 350 oC by resistive heating type metalorganic chemical vapor deposition method (MOCVD), respectively. The SrTiO3 was chosen as seed layers and prepared by pulsed laser deposition method. The crystal structures and orientations of SrTiO3 seeds were changed by deposition temperature. In the case of preparation with RF inductive heating MOCVD, the remanent polarization (2Pr) and coercive field (2Ec) were 42 μC/cm2 and 256 kV/cm, respectively.
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