[Paper] Stress dependence of growth mode change of epitaxial layered cobaltite γ-Na0.7CoO2




Stress dependence of growth mode change of epitaxial layered cobaltite γ-Na0.7CoO2J. Y. Son, Han-Bo-Ram Lee, and J. H. Cho, Applied Surface Science, 2007


http://dx.doi.org/10.1016/j.apsusc.2007.05.074


Abstract


We report stress dependence of growth characteristics of epitaxial g-Na0.7CoO2 films on various substrates deposited by pulsed laser deposition


method. On the sapphire substrate, the g-Na0.7CoO2 thin film exhibits spiral surface growth with multi-terraces and highly crystallized texture. For


the g-Na0.7CoO2 thin film grown on the (1 1 1) SrTiO3 substrate, the nano-islands of$30 nm diameter on the hexagonal grains are observed. These islands indicate that the growth mode changes from step-flow growth mode to Stranski–Krastanow (SK) growth mode. On the (1 1 1) MgO substrate, the large grains formed by excess adatoms covering an aperture between hexagonal grains are observed. These experimental demonstrations and controllability could provide opportunities of strain effects of NaxCoO2, physical properties of thin films, and growth dynamics of heterogeneous epitaxial thin films