Growth of Ca_xBa_1-xNb₂O₆ thin films on MgO(1 0 0) by pulsed laser deposition

Thin films of ferroelectric calcium barium niobate, Ca_xBa_1-xNb₂O₆, are deposited on MgO(1 0 0) substrates by pulsed laser deposition. The microstructure of the films is investigated by means of conventional and high-resolution transmission electron microscopy. The observation of plan-view and cross-sectional samples shows that the films are polycrystalline. The grains orient with their c-axis parallel to the normal of the film surface. Two sets of preferential in-plane crystallographic relationships are determined as 〈1 1 0〉_CBN//〈4 1 0〉_MgO and 〈1 0 0〉_CBN//〈3 1 0〉_MgO. Chemical reactions occur at the interface between the film and the MgO substrate, leading to the formation of two phases, corundum-type Mg₄Nb₂O₉ and pseudobrookite-type Mg₅Nb₄O₁₅.