Tatsuo Niwa

Ionic conductivity of tantalum oxide by rf sputtering

Abstract Tantalum oxide thin films were prepared by rf sputtering. The dependence of deposition conditions (i.e. sputtering power, total sputtering pressure, and oxygen partial pressure) on ionic resistivities for tantalum oxide films were evaluated. The proton conductivities varied from 3.3 × 10 −6 S/cm to −10 S/cm. The activation energy for ion motion varied from 0.25 to 0.4 eV; increasing exponentially with the optical absorption coefficient of the films. Variation in the ionic conductivities could be attributed to changes in the carrier concentrations and mobilities; although, a quantitative assessment was not made.

Degradation of the electrochromic nickel oxide film upon redox cycling

The degradation mechanism of electrochromic nickel oxide films by redox cycles was investigated. Films fabricated by sputtering of an oxide target were driven between the colored (oxidized) and bleached (reduced) states in 1 M KOH solution. With the cycles, the transmittance of the colored state decreased. While the peak potential of the redox became larger at first and then became smaller, the response time became rapid at first and slower afterward. The surface of heavily degraded films became uneven and easy to be removed. A higher oxidation voltage caused faster degradation. Heat treatment during deposition or making a film thicker was shown to affect durability.

Properties of tantalum oxide thin film for solid electrolyte

Abstract Tantalum oxide thin films were prepared by RF ion-plating and RF sputtering. Protonic conductivities of the films varied from 10 −5 to 10 −10 S/cm with the condition of deposition. The high ionic conductive film has low packing density and shows strong O-H absorption. It was concluded that the adsorbed water gives much influence to the protonic conduction.