Changes in electronic structure of La_x Al_y O films as a function of postdeposition annealing temperature

Amorphous La_x Al_y O films, containing 100, 50, and 30% La, were deposited by atomic layer deposition (ALD) on ultrathin Si O ₂ films (1 nm). Changes in the depth profile, as a function of composition, and structure were examined by medium energy ion scattering and transmission electron microscopy. The electronic structure of the La_x Al_y O films was investigated by X-ray photoelectron spectroscopy as a function of La concentration and postdeposition annealing temperature. In the case of a pure La₂ O₃ film without Al₂ O ₃, the Si O₂ at the interfacial layer had been converted to Si O2-x and La silicate during the ALD process. However, in case of a La ₂ O₃ film with Al₂ O₃, interfacial reactions were significantly suppressed. In particular, silicate formation in the La₂ O₃ films gradually increased with the increasing annealing temperature, while that in La₂ O₃ films incorporated Al₂ O₃ was suppressed up to an annealing temperature of 800°C.