Electroceramics in Japan IX

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Authors: Hyun Young Go, Naoki Wakiya, Keisuke Satoh, Masao Kondo, Jeffrey S. Cross, Kenji Maruyama, Nobuyasu Mizutani, Kazuo Shinozaki
Abstract: In this study, BiFeO3 (BFO) epitaxial film was deposited on SrRuO3 (100)/SrTiO3 (100) substrates using pulsed laser deposition (PLD). Phase pure BFO thin film was obtained. Introducing a mask between the target and substrate in PLD improved the surface roughness from 47.8 nm (RMS, without mask) to 7.7 nm (RMS, with mask). The composition and electrical properties of BFO thin film were assessed after annealing for 1 h in Ar, N2, or O2 atmosphere at 600°C. The P-E hysteresis properties improved only in the O2 atmosphere. After annealing under O2 atmosphere, the leakage current decreased from 6.1 × 10-2 A/cm to 2.9 × 10-2 A/cm at 200 kV/cm, as in the other annealing atmospheres, but 2Pr increased from 35 BC/cm2 to 50 BC/cm2.
Authors: Hiroshi Uchida, Hiroshi Nakaki, Hiroshi Funakubo, Seiichiro Koda
Abstract: The electrical properties of perovskite-based ferroelectric films were improved by ion modification using rare-earth cations. Thin films of rare-earth-modified lead zirconate titanate [Pb(Zr,Ti)O3] were fabricated on (111)Pt/Ti/SiO2/(100)Si substrates by a chemical solution deposition technique. The substitution of volatile cations in the simple-perovskite oxides, such as Pb2+ in Pb(Zr,Ti)O3 films, enhanced the insulating properties of the film. The crystal anisotropy of the Pb(Zr,Ti)O3 film could be controlled by varying the species and the amount of replacing cations to enhance the spontaneous polarization. Thus, ion modification using Dy3+ cation could enhance the remanent polarization of Pb(Zr,Ti)O3 film consequently.
Authors: Toru Onoue, Naoki Wakiya, Koichi Seo, Takanori Kiguchi, Nobuyasu Mizutani, Kazuo Shinozaki
Abstract: Pb(Zr0.05Ti0.95)O3/(La,Sr)CoO3 thin films were prepared by pulsed laser deposition (PLD) on SrTiO3(001) substrates. Phase transition behavior of Pb(Zr0.05Ti0.95)O3 (PZT) was investigated using high temperature X-ray diffraction (HT-XRD) and high-temperature electrical measurement. The phase transition temperature of PZT thin film is larger than bulk one. In 100 and 200nm-thickness epitaxial PZT thin films, the phase transition temperatures obtained from X-ray diffraction measurement and electrical property measurement are in good agreement.
Authors: Takeki Yamamoto, Naoki Wakiya, Nobuyasu Mizutani, Kazuo Shinozaki
Abstract: Epitaxial LiTaO3 thin films were deposited on epitaxial Pt(111)/Al2O3(001) and Al2O3(001) substrates by metal organic chemical vapor deposition using LiTa(OC2H5)4(OC2H4OCH3)2 and Li(DPM) precursors. The full-width at half-maximum of the rocking curve of LiTaO3 thin films were respectively 0.29° on Al2O3(001) substrates and 0.98° on epitaxial Pt(111)/Al2O3(001). Electrical measurements showed that the remanent polarization and coercive field of the films were 2Pr=76 μC/cm2 and E =130 kV/cm, respectively. The leakage current density was 10-6–10-8 A/cm2 at 120 kV/cm. Refractive indices n measured at 632.8 nm were measured respectively as 2.15 on Al2O3(001) and 2.14 on Pt(111)/Al2O3(001).
Authors: Masaaki Ichiki, Harumi Furue, Takeshi Kobayashi, Yasushi Morikawa, Kazuhiro Nonaka, Ryutaro Maeda
Abstract: Photovoltaic lead lanthanum zirconate titanate films in a layered structure of different crystallographic orientations are fabricated by an optimized metalorganic deposition method. Such films of (001) orientation exhibit a photovoltaic electrical power of approximately 20 times higher than that of random films. The anisotropic optical properties of the oriented films, including dark conductivity, photoconductivity and photovoltaic tensor surfaces, are obtained quantitatively. These results show that the photovoltaic output current and power of the oriented films are highly improved to be equal to those of semiconductors and suitable for application in the optical sensor of micro-electro-mechanical systems.
Authors: Keisuke Fujito, Naoki Wakiya, Takanori Kiguchi, Nobuyasu Mizutani, Kazuo Shinozaki
Abstract: Changes of residual stress and electrical properties were examined in (001)-oriented and (111)-oriented Pb(Zr0.5Ti0.5)O3 (PZT) thin films deposited on a buffered-Si substrate with a buffer and bottom electrode layer of a (La,Sr)CoO3(LSCO). A (001)-epitaxial PZT film was prepared on LSCO/CeO2 /Zr0.85Y0.15O1.93(YSZ)/Si. In addition, a (111)-oriented PZT film was prepared on LSCO/SrTiO3(ST) /Mn0.24Zn0.09Fe2.67O4(MZF)/YSZ/Si. The residual tensile stress in (001)-PZT thin films decreased from 2.92 to 1.98 GPa and the remanent polarization increased from 7.5 to 41.7 @C/cm2 as the LSCO thickness increased. In (111)-PZT, the residual tensile stress decreased from 1.72 to 0.95 GPa and remanent polarization increased from 9.5 to 26.7 @C/cm2. The residual tensile stress of (111)-PZT was less than that of (001)-PZT. The remanent polarization in the 80 nm (111)-PZT was greater than that of the 60 nm (001)-PZT. In the 700-nm-thick PZT, the remanent polarization in (001)-PZT was greater than that in (111)-PZT.
Authors: Masao Kondo, Kazuaki Kurihara
Abstract: The influence of a rare earth oxide/yttria-stabilized zirconia (YSZ) double buffer layer structure on the orientation of a perovskite thin film was investigated on (100) silicon substrates. A calcium titanate perovskite film with a mixture of (110) and (100) orientation was grown epitaxially on a YSZ buffer layer. Since rare earth oxides have almost the same chemical nature and different lattice parameters, it is anticipated that the lattice parameter of the buffer layer can be controlled by changing the rare earth element. An (100) oriented epitaxial calcium titanate film was obtained by changing the composition of rare earth oxides on the YSZ/Si substrate.
Authors: Kazuyuki Suzuki, Yi Ping Guo, Kaori Nishizawa, Takeshi Miki, Kazumi Kato
Abstract: The Y0.5Yb0.5MnO3 ferroelectrics/HfO2 stacking layer was constructed on Si(100) substrate through the chemical solution deposition. The HfO2 insulating layer crystallized on Si(100) substrates consisted of uniform grains and had smooth surface. The Y0.5Yb0.5MnO3 film prepared on the HfO2 insulator layer had preferred orientation along c-axis. The Y0.5Yb0.5MnO3 film consisted of uniform grains and had smooth surface. The clockwise C-V hysteresis induced by ferroelectric polarization switching was observed in the MFIS structure. The memory window of the MFIS structure was about 2 V and the retention time was over 105 s.
Authors: Yi Ping Guo, Kazuyuki Suzuki, Kaori Nishizawa, Takeshi Miki, Kazumi Kato
Abstract: BaTiO3 films with thickness of ~1 2m were prepared by chemical solution deposition on LaNiO3/Pt/TiOx/SiO2/Si substrate with a thin highly (100)-oriented and high crystallinity BaTiO3 thin film (~140 nm) as a buffer layer. The BaTiO3 films prepared by using a 0.5 mol/L solution have high crystallinity and still show (100) preferred orientation. The electrical properties of the (100)-oriented BaTiO3 films prepared by this process have been studied. A dielectric constant of ~910 and a loss tangent of ~3.5% (1 kHz) were obtained. The remanent polarization (2 Pr) and coercive field (2 Ec) are 4.0 μC/cm2 and 35 kV/cm, respectively.
Authors: Tadasu Hosokura, Akira Ando, Yukio Sakabe
Abstract: Epitaxially grown (Ba,Sr)TiO3 thin films were prepared on platinum-coated silicon substrate by sol-gel method using a (Ba,Sr)TiO3 sol derived from Ba(CH3COO)2, Sr(CH3COO)2 and Ti(O-i-C3H7)4. The morphology of the films was found to depend on the annealing condition. A columnar structure was obtained for (Ba,Sr)TiO3 thin film by annealing at 800 °C and a columnar grain was found to be single crystal by transmission electron microscope (TEM). The columnar grown film exhibits a preferred (111) orientation that follows the (111) orientation of Pt substrate. Measurement of the C-V in MFM was configured in order to demonstrate good dielectric properties. Obtained films showed high voltage tunability.

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