Yoshihiro Shintani

Energy Analysis of High-Energy Neutral Atoms in the Sputtering of ZnO and BaTiO3

The time-of-flight method has been employed to investigate the type and energy of high-energy neutral atoms bombarding the substrates in films of ZnO and BaTiO3 prepared by both DC planar magnetron sputtering and conventional DC diode sputtering. The high-energy neutral atoms are found to be oxygen atoms. The dependence of the flux of high-energy neutral oxygen atoms and negative oxygen ions on the pressure has also been measured for the planar magnetron sputtering of ZnO. It is shown that the high-energy particles bombarding the substrate are composed of neutral oxygen atoms at higher gas pressures ranging above 0.01 Torr, but negative oxygen ions are comparable with neutral oxygen atoms at pressures of the order of 10-3 Torr. The production mechanism of these energetic oxygen species is discussed.

Preparation of Thin BaTiO3 Films by dc Diode Sputtering

Direct current diode sputtering of reduced BaTiO3 ceramic has been applied to the preparation of thin BaTiO3 films. Sputtering was carried out over a range of apparent sputtering rates of ∼500–1200 mg/Ah in atmospheres of argon and air. As the substrate, Pt sheet and fused quartz were principally used. Grain size of the deposited film was ∼1000 A for the Pt substrate at 400°C. The lattice constants were in good agreement with those of ordinary BaTiO3 when the Pt substrate was kept at a temperature above 1000°C, although they were slightly larger for substrates below 900°C. Measurements of optical density and observations of electron micrographs indicated that the sputter‐deposited films have more favorable properties of transparency, uniformity, and crystallization than vacuum‐evaporated films. The film prepared on a Pt substrate at 1000°C in an air atmosphere had a dielectric constant of 1700 and dissipation factor of 1.8% without post‐deposition treatment. However, the remanent polarization was very sma...

Heteroepitaxial diamond growth on platinum(111) by the Shintani process

Abstract Diamond films with (111) facets were grown heteroepitaxially on Pt(111) using microwave plasma enhanced chemical vapor deposition. It was observed that many of the neighboring facets coalesced with each other. X-Ray diffraction analyses revealed that the (111) planes of diamond films were parallel to the substrate surface and azimuthally well oriented. The films were confirmed as diamond using Raman spectroscopy.

Preparation of conductive ZnO:Al films by a facing target system with a strong magnetic field

Abstract Transparent conductive ZnO:Al films were prepared in Ar gas by a planar magnetron sputtering system with facing targets, where strong internal magnets were contained in target holders to confine the plasma between the targets. A film resistivity of 4 × 10 −4 Ω cm was attained at a substrate temperature of 200 dgC. However, the film resistivity increased with increasing substrate temperature, due to a decrease of the carrier concentration. The reason for this phenomenon was the decrease of Zn donors in the film as native donors or an increase of Zn defects. When excess Zn atoms were supplied during film growth, a low resistivity of 2 × 10 −4 Ω cm was obtained even at a substrate temperature of 250 °C.

High-Energy Neutral Atoms in the Sputtering of ZnO

Dips were observed in the distribution curves of the deposition rates of ZnO films prepared both by planar diode and by planar magnetron sputtering. These dips are ascribed to high-energy neutral atoms bombarding the films. The influence of high-energy neutral atoms on the mixed orientation of ZnO film is also investigated in planar diode sputtering. In planar magnetron sputtering, which gives highly [002] oriented ZnO films, the correlation between the degree of c-axis orientation and the flux of high-energy neutral atoms is examined. It is found that high-energy neutral atoms should be considered when trying to obtain highly-oriented ZnO films.

Growth of highly (111)-oriented, highly coalesced diamond films on platinum (111) surface: A possibility of heteroepitaxy

A highly (111)-oriented, highly coalesced diamond film was grown on platinum (111) surface by microwave plasma chemical vapor deposition (MPCVD). Scanning electron microscopy and x-ray diffraction analyses revealed that the (111) diamond facets were azimuthally oriented epitaxially with respect to the orientation of the Pt(111) domain underneath, with the neighboring facets of diamond being coalesced with each other. The film was confirmed as diamond using Raman spectroscopy.

In situ and real-time observation of optical constants of metal films during growth

Abstract Optical constants of metal films with an average thickness in the 0–50 nm range have been studied by using the attenuated total reflection technique. The measurements were performed in situ during the growth of evaporated films. The effective optical constants of ultrathin discontinuous metal films have been evaluated precisely.

Influence of Bombardment by Energetic Atoms on c-Axis Orientation of ZnO Films

The influence of bombardment by high-energy particles on the c-axis orientation of ZnO films was investigated for DC diode sputtering with a hemispherical electrode system and for an RF cylindrical magnetron sputtering system. It was found that one of the criterions for preparing highly [002] oriented films is to decrease the flux and energy of high-energy particles bombarding the ZnO film without decreasing the deposition rate of the film. This criterion presents a guide to improving the degree of c-axis orientation in ZnO film in the fabrication of oriented film.

Behaviours of High-Energy Electrons and Neutral Atoms in the Sputtering of BaTiO3

In the sputtering of TiO3, the substrate exhibits an abnormal temperature rise and a considerable decrease in weight. To investigate these phenomena, an energy distribution of the electrons and the yield of high-energy neutral atoms were examined. Furthermore, the discharge currents due to electrons and positive tons were estimated separately, and the electron current was divided into the secondary electron and thermal emission currents. In BaTiO3. aconsiderable electron yield by thermal emission was detected. From the results obtained, the following conclusions maight be expected. The abnormal temperature rise of the substrate is due to many electrons impinging upon the substrate with relatively high energies, and the large yield of high-energy neutral atoms bombarding the substrate is responsible for weight diminution of the substrate.

Carbon nanofibers synthesized by decomposition of alcohol at atmospheric pressure

In the present study, we fabricated the carbon nanofibers (CNFs) by decomposition of methyl alcohol at atmospheric pressure. The CNFs were grown on Ni/Si substrates using simplified hot-filament chemical vapor deposition equipment. The deposits mainly consist of the semicrystalline CNFs, in which a few of carbon nanotubes are included. On the 30-nm-thick Ni/Si substrates, the mean length of the CNFs is 2–3 μm, and their average diameter is less than 100 nm. The as-deposited CNFs were evaluated by both scanning and transmission electron microscopes. The field-electron-emission properties of CNFs were characterized as well.