Tatsuo Fukami

Platinum doped titania film oxygen sensor integrated with temperature compensating thermistor

Abstract A TiO2:Pt cermet film oxygen sensor for detecting excess air ratio λ was prepared by tripole magnetron sputtering system. Fast response and high sensitivity were observed in the neighborhood of a stoichiometric point mainly due to the dispersion of catalytically active platinium in atomic order. The a.c measurement shows that the influence of the electrode contact is the origin of asymmetry in the Cole-Cole plot in low frequency range. The TiO2:Pt film sensor integrated in series with ZnCr2O4 or TiO2:V2O5 film thermistor yields a stable output regardless of temperature fluctuation in the temperature range of interest.

Dependence of Resistivity on Donor Dopant Content in Barium Titanate Ceramics

Barium titanate ceramics doped with yttrium as well as silica and alumina have been studied with special reference to the effects of the yttrium content. An yttrium content at which the ceramics showed a minimum resistivity increased with the increase of the sintering temperature and the added amounts of SiO2Al2O3. The microstructural studies with the electron probe X-ray microanalyzer revealed that these results should be explained in terms of the grain growth inhibitor effects of yttrium and the segregation of it to grain boundaries.

Dielectric and Conduction Properties in Nickel Doped Barium Strontium Titanate Ceramics

Electrical properties of defect structure in Ni-doped (Ba1-xSrx)TiO3 ceramics were studied by means of electron spin resonance (ESR), thermally stimulated current (TSC), dielectric and conduction measurements. A set of experimental results revealed that the nickel cations were located on the B-site of the perovskite in the form of Ni2+ and mainly Ni3+ leading to a slight increase of the diffusion characteristics of the para-ferroelectric transition and that the enhanced electric conduction observed at high temperatures is due to oxygen vacancy migration towards the cathode.

Observations on the operation of a planar magnetron sputtering system by target erosion patterns

Abstract The discharge characteristics in a planar magnetron sputtering system was studied by means of the target erosion pattern. The erosion pattern was affected not only by the magnetic flux distribution but also by the discharge power and the sputtering gas pressure. A model analysis revealed that this behaviour was due to interaction between the vertical component of the field and electrons moving in a sideways direction. It was found from its definite correlation with the pattern that the transition in the discharge characteristic from a magnetron mode to a high impedance mode was brought about by the escape of trapped electrons from the target edge.

Ferroelectric Films Deposited by Reactive Sputtering and Their Properties

Thin films of ferroelectric materials (PZT and PLZT) have been deposited by dc reactive co-sputtering from composite metal target. Although the structure of the resulting films without substrate heating was proved as amorphous through X-ray diffraction, it can be changed to provide a desired perovskite structure by subsequent heat-treatment in a lead-compensated atomosphere. Some of the films, after poling in the planar direction, showed an obvious piezoelectric activity.

Dislocation-Free Czochralski Si Crystal Growth without the Dash-Necking Process : Growth from Undoped Si Melt

Dislocation-free Si crystals have been grown successfully by the Czochralski (CZ) method without the Dash-necking process. It was found that the boron concentration limit in the seed for no dislocation formation due to thermal shock was 1×1018 atoms/cm3, and the maximum admissible discrepancy of boron concentration in the seed and in the crystal was 7×1018 atoms/cm3 for no dislocation formation in the crystal due to the lattice misfit. Consequently, it is revealed that dislocation-free CZ-Si crystals can be grown from undoped Si melt without the Dash-necking process when a seed with a suitable boron concentration is used.

Low-temperature formation of photocatalytic Pt-anatase film by magnetron sputtering

Films of TiO2 dispersed or coated with platinum were deposited on glass and Pt-buffered polyamide substrates respectively by magnetron sputtering. The photocatalytic activity of the films was evaluated through the decomposition of acetic acid under UV irradiation. The Pt-dispersed TiO2 film of approximately 1.5 wt % platinum shows a maximum activity due to for the formation of anatase phase with a fine grain size. Platinum particles ∼20Å in thickness coated on anatase film greatly improves activity. The activity shows a steplike dependence of film thickness where the critical thickness varies between 150 and 200 nm depending on the deposition temperatures. The correlation between defects and activity was verified by measuring either the temperature dependence of electric resistance or the shift of binding energy from XPS.

Design principles for multilayer piezoelectric transformers

Abstract Multilayer piezoelectric transformers with various internal electrode patterns have been studied in this paper. Dependence of the electrical properties of transformers on the number of layers was examined and then design principles are indicated about it. The multilayer piezoelectric transformer is superior to the conventional one in view of large output current.

Heavily Boron-Doped Silicon Single Crystal Growth: Boron Segregation

Heavily boron-doped silicon single crystals have been grown successfully by the Czochralski (CZ) method. The limit of boron concentration in the silicon melt for dislocation-free silicon crystal growth and segregation with heavy boron doping were investigated. It was found that a dislocation-free silicon crystal could be obtained even when the initial boron concentration in the silicon melt was up to 3.8×1020 atoms/cm3 with a solidified fraction of about 0.5. The lowest resistivity of the dislocation-free B-doped silicon crystal was about 0.7 m Ωcm. It is confirmed that the equilibrium segregation coefficient of boron decreases from 0.8 with heavy boron doping.

Highly C-Axis-Oriented Pb(Zr, Ti)O3 Films Prepared by Sputtering

A newly developed tripole magnetron sputtering system, which has a third magnetic pole, has been applied to deposit PZT films in the atomic layer epitaxy mode. A set of experimental results revealed that the resultant films were highly c-axis orientated on (100) MgO substrates and that the deviation from stoichiometry in the films enhanced asymmetric properties of the P-E loop patterns.