Tsutomu Yamazaki

Influence of thickness on H2 gas sensor properties in polycrystalline SnOx films prepared by ion-beam sputtering

Amorphous SnOx films were deposited on sintered alumina substrates by ion-beam sputtering. They were annealed at 500° C for 2 h in air and polycrystalline films with thickness varying from about 1 to 700 nm were prepared. Film-sensor properties against 0.47% H2 gas were measured as a function of thickness and the operating temperature for 150 to 350° C. The film thickness exhibiting a sensitivity maximum increased gradually with temperature. The optimum thickness shifted from 7 nm at 150° C to 175 nm at 350° C. Highly sensitive films lay in a narrow thickness range of 60 to 180 nm and films thinner or thicker than this were relatively insensitive at 300 and 350°C. A model was proposed to interpret the sensitivity behaviour in terms of thickness and grain-boundary effect.

Thickness dependence of H2 gas sensor in amorphous SnQx films prepared by ion-beam sputtering

Amorphous SnOx films were deposited by ion-beam sputtering on sintered alumina substrates. Amorphous film sensors were prepared by annealing the films at 300° C for 2 h in air. The thickness dependence of resistivity and hydrogen gas sensitivity were measured at 150° C over the thickness range ∼ 1 to 700 nm. A resistivity maximum was observed in ultrathin films. Resistivity increased by three orders of magnitude with increasing film thickness from 0.9 to 7.4 nm and then decreased by five orders of magnitude from 7.4 to 35 nm. Ultrathin film sensors showed sensitivity maxima around a thickness of 10 nm. Sensitivity and resistivity of ultrathin films were significantly influenced by the thermal expansion coefficient and the surface state of the substrate.

Composition dependence of superconductivity in the YBa2−xMxCu3Oy system

This letter reports the influence of 36 M elements on the T c,end of the superconductor YBa 2−x M x Cu 3 O y . Furthermore, some combination of two species was tried as heterovalent-ion dopants, instead of doping a single M element. Samples were prepared from reagent-grade powders of oxides (M=Mg, Y, Ce, Gd, Yb, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi, Te) and carbonates (M=Li, Na, K, Rb, Ca, Sr, Ba, La)

High gas sensitivity of tin oxide ultrathin films deposited on glasses and alumina substrates

Tin oxide ultrathin films were deposited on optically flat Pyrex glass, optically flat quartz glass and sintered alumina substrates by the ion-beam sputtering method. Films with thickness varying from about 1 to 500 nm were annealed in air at 500 °C for 50 h. The gas sensing properties of these films were investigated at 300 °C against synthetic air containing 0.5% hydrogen. A small substrate dependence of sensor behaviour was observed; however, an overwhelmingly important thickness dependence occurred in all substrates tried. Sensitivities higher than ∼104 or 105 were obtained in films in a narrow thickness range of about 3 to 20 nm, and films thicker or thinner than this were relatively insensitive.

An application of oxide and silver electrode on the BaO-doped Bi2O3 electrolyte

Abstract Oxide and silver paste were applied on the BaO-doped Bi 2 O 3 electrolyte and their behavior was studied as a function of temperature and oxygen partial pressure. Interface resistance of most oxide/electrolyte were of the same order of magnitude with those of Ag paste/electrolyte in air (300–500°C). A high electrode capacitance of (0.8–1.7)×10 −2 F/cm 2 was observed for the silver electrode at 450°C in the P O 2 region of 1–10 −5 atm.

DC-plasma-assisted synthesis of diamond and alumina using liquid

Abstract A new approach was proposed for the DC-plasma-assisted ceramic synthesis using liquid as starting materials. The method consists of generating a plasma between the substrate (electrode) and the liquid phase. Plasma-assisted deposition above the liquid surface of a water-ethylene glycol solution yielded diamond on anode substrate under a constant applied voltage. The morphology and quality of diamond changed from mirror-ball particle with disordered graphite to high-quality film with prolonged deposition. Heating a cathode wire by discharge in an aqueous solution of aluminum nitrate produced α-alumina coatings without post-annealing under atmospheric pressure. Deposition stopped automatically when the whole wire in the solution was covered with alumina. The growth rate of the alumina coatings ranged 1–10 μm min −1 .

The first synthesis of organosilyl-substituted aluminophosphate molecular sieves

Organosilyl groups were successfully incorporated in AFI and VFI aluminophosphate frameworks using organoalkoxysilanes to modify hydrophobicity and acidity of the molecular sieves.

Effect of platinum distribution on the hydrogen gas sensor properties in tin oxide thin films

Tin oxide and platinum layers were deposited on oxidized silicon wafers by ion-beam sputtering. The hydrogen gas sensing properties of undoped films and platinum-doped films were examined at 300°C for films annealed at 500°C. It was observed that the surface platinum when annealed together with the tin oxide film increased the sensitivity and reduced the response time compared with those of undoped films. Longer annealing tended to shift the optimum sensor thickness to a thicker side; the optimum thickness changed from 17 to 37 nm as the annealing time increased from 2 to 50 h. The interdiffusivity between the platinum and the tin atoms in the bulk was negligibly small at 300°C.

Properties of indium oxide/tin oxide multilayered films prepared by ion-beam sputtering

The preparation and characterization of indium oxide (InOx)/tin oxide (SnOy) multilayered films deposited by ion-beam sputtering are described and compared with indium tin oxide (ITO) films. The structure and the optoelectrical properties of the films are studied in relation to the layered structures and the post-deposition annealing. Low-angle X-ray diffraction analysis showed that most films retained the regular layered structures even after annealing at 500° C for 16 h. As an example, we obtained a resistivity of 6×10−4 Ω cm and a transparency of about 85% in the visible range at a thickness of 110 nm in a multilayered film of InOx (2.0 nm)/SnOy (0.2 nm)×50 pairs when annealed at 300° C for 0.5 h in air. Hall coefficient measurements showed that this film had a mobility of 17 cm2 V−1 sec−1 and a carrier concentration (electron density) of 5×1020 cm−3.

Study on the Development of Resource-Saving High Performance Slurry - Polishing/CMP for Glass Substrates in a Radical Polishing Environment, Using Manganese Oxide Slurry as an Alternative for Ceria Slurry

While investigating polishing mechanism of glass substrates with ceria abrasives (CeO2), we found its oxidizing properties worked effectively for the polishing. This finding has inspired us to speculate about the possibility of the manganese oxide abrasives as an alternative for ceria as they also have oxidizing properties. Therefore, focusing on the valence of the manganese, we have experimentally manufactured MnO, MnO2, Mn2O3 and Mn3O4 abrasives, and conducted a comparison study of the characteristics obtained with ceria slurry and manganese oxide slurries. As a result, the surface roughness of below Ra 0.8nm obtained with Mn2O3 slurry was found better than that with the conventional ceria slurry, on top of which, its removal rate was as good as or equal to that of ceria. Using a novel, closed type CMP (Chemical Mechanical Polishing) machine, we conducted another glass polishing experiment with ceria and manganese oxide slurries. The inside of the CMP machine was filled with high-pressure gases such as oxygen, air and nitrogen and kept at 500kPa to make the polishing environment radical. Through this experiment, we found an effective polishing method for high-quality surface. The removal rates were several times better than that of the conventional polishing performed in an open CMP machine.