Investigation of epitaxial growth of La₂Zr₂O₇ thin films with different carbonaceous phases

Abstract

During the metal–organic deposition (MOD) process, the carbon-rich impurities remaining in a film are harmful to the epitaxial growth of the oxide film. Thus, it is of great importance to investigate epitaxial growth of oxide films with different carbonaceous phases. To control the carbonaceous phases in the as-fabricated LZO film, different dopant concentrations and annealing atmospheres have been suggested during the MOD process. A characterization of specimens was performed using X-ray diffraction θ–2θ scans, out-of-plane and in-plane scans, X-ray photoelectron spectroscopy, electron backscattering diffraction, and atomic force microscopy. It was found that a small number of carbonaceous phases, regardless of their type, has no obvious negative influence on the growth orientation of the film. Moreover, because some bridge-pillar spots in the graphene layer enable the epitaxial growth of oxide film, the texture degree of LZO film doped with a high concentration of reduced graphene oxide (RGO) is even sharpened. With increasing doping RGO concentration, the surface roughness of the LZO film increases, which indicates an exaggerated impact of the surface defects on the metallic substrate on the grain size of the LZO film doped with RGO. Different oxygen partial pressures in the annealing atmosphere determine the type of carbonaceous phase in the as-prepared oxide film. The carbonate species formed in the film under high oxygen partial pressure have a negative influence on the texture degree and the surface flatness of LZO film, while low oxygen partial pressure favors the reduction of the residual carbon in the film. Therefore, oxide films with high performance can be achieved by controlling the presence of the positive carbonaceous phases in the film during the introduction of an appropriate artificial doping source and the selection of a suitable annealing atmosphere.