Hisamochi Harada

The preparation of transparent ZnO: Al thin films

Abstract Transparent conductive ZnO: Al films were prepared by the facing-target-type sputtering method. The films typically showed poor conductivity immediately after sputtering. However, at optimum conditions, they manifested their lowest resistivity of 4×10 -4 Ω cm after heat treatment at 400°C. The decrease in resistivity is mainly attributed to the improvement of the Hall mobility which in essence is not due to crystallinity improvement, but rather due to the decrease of excess oxygen atoms at the interstitial state or the grain boundaries. However, even without heat treatment we obtained a low resistivity of 5.3×10 -4 Ω cm under low oxidation sputtering condition at 0.1 Pa with oxygen to argon ration of 1:4.

XPS Studies of Bi-Sr-Ca-Cu-O Single Crystal and Ceramics Surfaces

The XPS (X-ray photoelectron spectroscopy) spectra from (a) the cleaved surface of a single crystal, (b) the polished surface and (c) the Ar+-sputtered surface of the ceramics in Bi-Sr-Ca-Cu-O are mecnsured and compared. The chemical bond nature of Bi is the same in all three surfaces. Sr and Ca in (c) are more oxidized than those in (a). In (b), there are two kinds of Sr and Ca, one from a clean surface like the cleaved surface region, and the other, more oxidized Sr and Ca which exist in the Ar+-sputtered surface. Cu2+ is dominant in (a) and (b), while Cu+ is dominant in (c). The O 1s XPS spectrum from (c) is sharper and narrower than that from (a). This may be due to the existence of isolated metal oxides of Sr, Ca and Cu by Ar+-sputter etching.

Mossbauer Study of Fe-Zr Alloys Formed at Interfaces between Fe and Zr Thin Films

The Mossbauer spectra of Zr films evaporated on Fe substrates (Zr/Fe) and Fe films on Zr substrates (Fe/Zr) were measured after heat treatments following evaporation. Fe2Zr was detected in the interfaces of both Zr/Fe and Fe/Zr films after heat treatments above 900°C, while, FeZr3 was detected in the Fe/Zr films treated below 900°C. FeZr2 was not detected in both films but FeZr2Ox was observed in Fe/Zr films annealed at 1000°C. The relative amounts of intermetallic phases, which were formed at interfaces, suggest that diffusion of Zr atoms into the Fe substrates mainly occurs in Zr/Fe, whereas diffusion of Fe atoms into Zr substrates is a major process for making intermetallic compounds in Fe/Zr at rather low temperatures.

Characteristics of ZnO:Al Transparent Conductive Films

Conduction mechanism of sputtered ZnO:Al thin film was studied for developing heat resistant transparent electrodes of EL devices. Strong evidence of the formation of the Al donors in ZnO:Al films was obtained by XPS measurements. X-ray diffraction measurements showed that the decrease of the mobility with increasing Al concentration above 1.3% was partly due to the low crystallinity of the films.

Adsorption of Oxygen SnOx Thin Film

The change in electrical resistance and the surface potential of SnOx thin film by the adsorption of oxygen were observed. At an oxygen pressure of 6.7×10-4 Pa, both changes result in a decrease. At further adsorption, the change in the electrical resistance ascends abruptly at about 10-2 Pa. These changes can be explained by devising a model of band bending.