Transmission electron microscopy study of epitaxial lanthanum–manganite thin films on SrTiO₃

Abstract

The microstructure of lanthanum manganite (La_1−xMnO_3−δ) thin film on strontium titanate (SrTiO₃) substrate fabricated by liquid chemical vapour deposition has been studied by transmission electron microscopy. Both La_1−xMnO_3−δ and SrTiO₃ have a perovskite structure with lattice misfit about 1% but there is no evidence for correlation of the density of the misfit dislocation and misfit. In the vicinity of the interface between La_1−xMnO_3−δ and SrTiO₃, the misfit is accommodated by a distortion of the lattice of La_1−xMnO_3−δ. At the areas not adjacent to the interface of La_1−xMnO_3−δ SrTiO₃, small particles, which can be identified as MnO, are found to be associated with the misfit between La_1−x,MnO_3−δ and SrTiO₃. The MnO phase is unstable with respect to La_1−xMnO_3−δ. The growth of a thin film of La_1−xMnO_3−δ on SrTiO₃ is epitaxial and an orientation relationship is (100)_{La1−xMnO3−δ} //(100)_SrTiO3 //(100)_MnO and [010]_{La1−xMnO3−δ} //[010]_{La1−xMnO3−δ} //[010]_SrTiO3 //[010]_MnO. The interface of La_1−xMnO_3−δ-SrTiO₃ is composed of Ti and Mn atoms plus oxygen.