Fabrication of Na xCoO2 thin films by pulsed laser deposition

In this paper, we report the growth of Na xCoO2 thin films by pulsed laser deposition. Single β-Na xCoO2 phase films showing metallic conducting behavior were obtained. The surface morphology of these films showed granular features. The films were stable in vacuum or in the pure oxygen environment, but were not stable in air, causing their resistivity to increase exponentially with time and become semiconductors or insulators. X-ray diffraction measurements confirmed that the (00l) orientation of the films did not change during this degradation of the films. The results suggest that the resistivity increase of the films is related to the appearance of some impurity phase at the grain boundaries of Na xCoO2 due to reaction with moisture