High-quality epitaxial BaTiO3 films grown by high-vacuum chemical vapor deposition for integrated electro-optical devices

Abstract

Synthesizing high-quality epitaxial BaTiO₃ (BTO) by means of high-vacuum chemical vapor deposition (HV-CVD) requires a precise control over precursor fluxes impinging onto the heated substrate surface so that the incorporation rates of all elements correspond to the BTO film stoichiometry. Moreover, overall precursor flux magnitude strongly influences the morphology of the film grown at a given substrate temperature. HV-CVD in a combinatorial mode allows to explore a wide range of fluxes over the substrate surface in a single synthesis, saving a lot of time on process optimization. Owing to the high vacuum during synthesis, the precursor trajectories are ballistic, thus the fluxes at the location on the substrate of the best film quality are analytically evaluated. The optimized conditions are transferred into a uniform deposition mode on SrTiO₃-buffered substrate for epitaxial compatibility and further fine-tuned for the improved film quality. The obtained films are characterized by SEM, EDX, XRD, AFM, ellipsometry and RBS/HI-ERDA elemental analysis. The characterization confirms that the films are stoichiometric and pure, highly oriented (XRD rocking curve FHWM <1°), near-atomically smooth, and of minimal porosity (∼1–3 % void content). The results indicate that BTO films of excellent quality are achievable using this highly scalable and competitively cost-effective technique.