Structure determination of MnO₂films grown on single crystalα-Al₂O₃substrates

Abstract Manganese oxide films have been grown by atomic layer deposition and investigated using electron diffraction and high-resolution electron microscopy (HREM). The films were deposited on the (001) surface of monocrystalline α-Al2O3. The films were found to consist of an ordered version of the hexagonal ε-MnO2 (Akhtenskite) type. Using X-ray diffraction, the cell parameters were determined to be a = 2.75(2) Å and c = 4.302(5) Å. The films are epitaxial with a specific orientation relative to the Al2O3 substrate. The [210] and [001] axes of ε-MnO2 are parallel to the [110] and [001] axes of α-Al2O3, respectively. Evidence of cation ordering was found by parallel beam electron diffraction. The ordered domains are needle shaped with widths of 2–10 nm. The unit cell of the ordered structure was found to be orthorhombic with cell dimensions a = 2.75, b = 4.76, c = 4.302 Å and space group Pmnn (No. 58). Acknowledgement We thank the Norwegian Research Council for financial support through project FIN (Films, Interfaces and Nanomaterials).