Characterization of the Interface Between Lanthanum Hexa-Aluminate and Sapphire by Exit Wave Reconstruction

Epitaxial thin films of rare-earth hexaaluminates on basal plane sapphire have been produced by chemical solution deposition. LaAl11O18 films with magnetoplumbite structure grow with (0001)HA||(0001)S and [1100]HA||[2110]s orientation relationshipTo investigate the stucture of the interface exit wave reconstruction of focus series was carried out using a field emission TEM. Due to the inversion of the imaging process major artefacts at the interface can be eliminated. Exit waves were simulated based on different interface models and were compared with the reconstructed waves to localize the positions of the atoms at the interface. Two different types of interfaces were observed in the samples. One of the types, in which the spinel block of hexaaluminate faces the sapphire with the mixed cation layer with occupied octahedra and tetrahedra, is characterized in detail. Face-sharing of coordination polyhedra is avoided to large extent