Preparation of oriented Co₃O₄ films by decomposition of Na_XCoO₂

Miroslav Soroka, Josef Buršík

Institute of Inorganic Chemistry AS CR, v. v. i., Husinec‑Řež 1001, 25068 Řež, Czech Republic

 

Materials based on cobalt oxides have attracted great interest in the production of electronic thin films, heterogeneous catalysts, and gas sensors. In this work we studied the formation and structural characterization of highly (111) - oriented Co₃O₄ (cubic spinel structure) films prepared by novel procedure from (001) - oriented layered sodium cobaltate Na_XCoO₂. The Na_xCoO₂ films exhibits self-texture growth with crystallographic c-axes perpendicular to the film plane independently of substrate used for deposition.

The Na_xCoO₂ films with different contend of sodium were deposited on single crystal and ceramics substrates by chemical solution deposition (CSD) and crystalized by annealing at temperature of 700 °C. Subsequently, the (111) - oriented Co₃O₄ films were obtained during post- growth annealing at the temperature of 900 °C. Films were mainly characterized by X-ray diffraction, scanning electron microscopy (SEM), and atomic force microscopy (AFM).

The Co₃O₄ grows (pseudo)epitaxially with the epitaxial relation Co₃O₄ (111)[-121] // α–Al₂O₃ (0001)[10-10] as determined from φ scan and pole figure measurements. The degree of preferred orientation observed in Co₃O₄ depends on the content of Na in starting Na_xCoO₂ phase.

This work was supported by the Grant Agency of Academy of Sciences of the Czech Republic under Grant No.13-03708S.