Synthesis and characterization of (111)-oriented BaTiO₃ thin films

The synthesis of (111)-oriented BaTiO₃ thin films on Nb-doped SrTiO₃ and bilayers of BaTiO₃ and La_0.7Sr_0.3MnO₃ on SrTiO₃ are investigated. With increasing thickness the films are found to exhibit a decreasing out-of-plane lattice parameter and increased surface roughness. The BaTiO₃ films on doped SrTiO₃ are found to be relaxed with indications of increasing defect density with increasing thickness. Through piezoresponse force microscopy, pyroelectric measurements, and tunneling electroresistance measurements, indications of ferroelectric behavior are found in (111)-oriented BaTiO₃ down to a thickness of 5 nm. (paper)