Papers by Author: Hiroshi Funakubo

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Authors: Daisuke Nagano, Mitsunori Sugiura, Naoki Wakiya, Hiroshi Funakubo, Kazuo Shinozaki, Nobuyasu Mizutani
Authors: N. Nukaga, Ishikawa Kunio, Kazuo Shinozaki, Nobuyasu Mizutani, Hiroshi Funakubo
Authors: Yuki Mizutani, Junichi Kimura, Itaru Takuwa, Tomoaki Yamada, Hiroshi Funakubo, Hiroshi Uchida
Abstract: Thin films of MBi4Ti4O15 (M = Ca and Sr) with preferential crystal orientation were fabricated using underneath perovskite layers on various substrates. One-axis BLSD films on (100)LaNiO3/(111)Pt/Ti/(100)Si and epitaxial BLSD films on (100)SrRuO3//(100)SrTiO3 were fabricated by chemical solution deposition (CSD). Dielectric constants of the CaBi4Ti4O15 and SrBi4Ti4O15 films on (100)LaNiO3/(111)Pt/Ti/(100)Si were approximately 250, while those on (100)SrRuO3//(100)SrTiO3 were 220, respectively. The temperature coefficients of capacitance (TCCs) of these films were below 10% in atmospheric temperature range between R.T. and 300°C, which is significantly smaller than those of conventional (Ba,Sr)TiO3-based capacitors.
Authors: Yuki Mizutani, Hiroshi Uchida, Hiroshi Funakubo, Seiichiro Koda
Abstract: Thin films of a bismuth layer-structured dielectric oxides (BLSD), SrBi4Ti4O15, with preferential crystal orientation were prepared by means of chemical solution deposition (CSD) technique on (111)Pt/(100)Si substrate with bottom nucleation layers of conductive perovskite oxides, LaNiO3 and SrRuO3. CSD technique was utilized for the film preparation of SrBi4Ti4O15. These films possessed highly crystal orientation of (00l) BLSD planes parallel to the substrate surface. The leakage current densities of the SrBi4Ti4O15 films on (100)SrRuO3//(100)LaNiO3/(111)Pt/Ti/(100)Si and on (100)LaNiO3/(111)Pt/Ti/(100)Si were approximately 10-6 and 10-7 A/cm2 respectively. The dielectric constants of these films in a frequency range of 102 - 106 Hz were from 310 to 350 and 250 to 260 respectively. The value of capacitance change of these films in the range from 20 to 300 oC was about +8 and +5% respectively.
Authors: Hiroshi Funakubo, M. Yonetsu, Kazuo Shinozaki, Nobuyasu Mizutani, M. Ishikawa, Naoya Sakai, Harumi Yokokawa
Authors: Masaki Hirano, Kazuhisa Kawano, Hiroshi Funakubo
Abstract: The deposition mechanism of metal-Ru films including incubation time was investigated for Ru films prepared by metal organic chemical vapor deposition from (2,4-Dimethylpentadienyl)(ethylcyclopentadienyl)Ruthenium (DER) - O2 system. Substrates with amorphous top-layer having various Hf/Si ratio, SiO2 (native oxide)/(001)Si (SiO2), HfSiON/SiON/(001)Si (HfSiON) and HfO2/SiON/(001)Si (HfO2), were used as substrates. The deposition temperature dependence of the deposition amount at the fixed deposition time ranging from 210 oC to 300 oC revealed that the deposition amount depended on the deposition temperature below 250 oC, while it was almost constant above this temperature. Incubation time depended on the kinds of substrate at 210 oC and the substrate surface was fully covered in a shorter time with smaller deposition amount for the substrates with shorter incubation time. In addition, the film with shorter incubation time had smaller surface roughness.
Authors: Hiroshi Funakubo, Shingo Okaura, Muneyasu Suzuki, Hiroshi Uchida, Seiichiro Koda
Abstract: Effect of annealing temperature on the dielectric properties of Bi1.5Zn1.0Nb1.5O7 films prepared on (111)Pt//(001)Al2O3 and (111)Pt/fused silica substrates by MOCVD was investigated. The tunability and the inverse of the dielectric loss [1/ (tan )] increased with increasing annealing temperature. Relative dielectric constant and temperature coefficient of the capacitance (TCC) increased with the crystallinity of the films. On the other hand, (1/tan ) was independent of the crystallinity of the films, but was dramatically increased by the annealing.
Authors: Daisuke Nagano, Hiroshi Funakubo, O. Sakurai, Atsushi Saiki, Kazuo Shinozaki, Nobuyasu Mizutani
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.
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