Kinetically Controlled Thin-Film Growth Of Layered Beta- And Gamma-Naxcoo2 Cobaltate

We report growth characteristics of epitaxial beta-Na0.6CoO2 and gamma-Na0.7CoO2 thin films on (001) sapphire substrates grown by pulsed-laser deposition. Reduction of the deposition rate could change the structure of the NaxCoO2 thin film from a beta phase with an island growth mode to a gamma phase with a layer-by-layer growth mode. The gamma-Na0.7CoO2 thin film exhibits spiral surface growth with multiterraced islands and highly crystallized texture compared to that of the beta-Na0.6CoO2 thin film. This heterogeneous epitaxial film growth can give an example of the strain effect of physical properties and growth dynamics of NaxCoO2 as well as the subtle nature of structural change. (c) 2005 American Institute of Physics.