The stability of zinc oxide transparent electrodes fabricated by R.F. magnetron sputtering

The stability of the electrical, optical and mechanical properties of sputtered zinc oxide (ZnO) thin films with resistivities from 10^?2 to 10^?4 ωcm were investigated. No significant changes in these properties are observed for ZnO films exposed to air at room temperature for 10 months. A change in the electrical resistance of the ZnO films with temperature up to 400 °C is observed in various ambients such as vacuum, inert gases and air. After heat treatment in these ambients at 400 °C, the resistivity of the films increased by one to ten orders of magnitude. The increased resistivity can be returned to the resistivity of the virgin state, within one order of magnitude, by heat treatment in a hydrogen ambient at temperatures near 400 °C. For practical use of ZnO films at high temperatures, the increase in the resistivity might become a disadvantage for ZnO transparent electrodes fabricated by r.f. magnetron sputtering.