Osamu Tada

Influence of Energetic Oxygen Bombardment on Conductive ZnO Films

Conductive ZnO films were prepared by DC planar magnetron sputtering and DC diode sputtering, and the reason for the high resistivity shown by the films at the substrate positions facing the eroded area of the target was investigated. It was found that bombardment of the film by energetic O atoms or O- ions is responsible for the high film resistivity, since this results in a decrease in both the carrier mobility and the carrier concentration. The arrival of excess O atoms and O- ions with relatively lower energies also induces an increase in the film resistivity as a result of a decrease in carrier concentration. The positional dependence of the film resistivity is explained by considering the above two factors.

Radiation Effect due to Energetic Oxygen Atoms on Conductive Al-Doped ZnO Films

Al-doped ZnO films were prepared by both RF planar magnetron and RF diode sputterings. The dependence of the ZnO film resistivity on both substrate position and Ar gas pressure was investigated. Energetic oxygen atoms (O atoms) bombarding the film were also observed by time-of-flight apparatus, and the correlation between the film resistivity and the film bombardment by the energetic O atoms was examined. The following results were obtained: When the bombardment of energetic O atoms on Al-doped ZnO films became significant at the substrate positions facing the eroded area of the target, the film resistivity increased at the same positions. Then, both the carrier concentration and Hall mobility of the Al-doped ZnO films were decreased, which was thought to be due to the film bombardment by the energetic O atoms.

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.

Experimental Observation of Long-Range Surface Plasmon Polaritons

ATR technique (glass prism-index matching oil-Ag-CaF 2 single crystal) has been used to observe long-range surface plasmon polaritons discussed recently by Sarid. At 632.8 nm, we have successfully ...

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...

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.

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.

Long-Range Surface Plasmon Polaritons in Metal Films Bounded by Similar-Refractive-Index Materials

We have numerically and experimentally investigated the propagation characteristics of surface plasmon polaritons (SPs) in metal films bounded by materials with very similar refractive indices. The calculation indicates that the SPs can propagate over macroscopic distances in the visible region. ATR experiments for angle scans (glass prism-index matching oil-Ag film-Pyrex glass) have shown that a propagation length of ∼200 µm can be readily gotten at 632.8 nm wavelength under an appropriate condition.

In Situ Studies on Oxidation of Copper Films by Using ATR Technique

Oxidation studies of copper films at room temperature have been carried out by measuring the ATR spectra involving information about surface plasmon polariton characteristics. Oxidation is initially rapid, but after 10 to 20 minutes, drops to a negligible value, a stable film being formed ∼2.7 nm thick. It has been furthermore confirmed that copper oxide films formed in 20 Torr of oxygen at room temperature are composed of a mixture of Cu and CuO 0.67 (gross defect structure of Cu 2 O) in the first stage of oxidation, but the final composition becomes CuO 0.67 .