INFLUENCE OF THE MICROSTRUCTURE OF PT SI SUBSTRATES ON TEXTURED GROWTH OF BARIUM-TITANATE THIN-FILMS PREPARED BY PULSED-LASER DEPOSITION/

Pt-coated silicon substrates with strong (111) Pt texture were anneale d in an oxidizing atmosphere at temperatures from 500 degrees C to 750 degrees C. BaTiO3 thin films were deposited by pulsed laser ablation on the substrates. Observation by transmission electron microscopy sho wed that the substrate anneal caused the formation of TiO2 in the Pt l ayer, accompanied by the formation of a high density of faceted protru sions on the Pt surface, particularly at the higher anneal temperature s. The Pt protrusions had (111) facets, parallel to the substrate surf ace, on which (100)-oriented BaTiO3 grains were observed. BaTiO3 grain s with an epitaxial relationship to the Pt lattice were observed on in clined facets of the Pt protrusions [which were not (111) planes], and also on the nonplanar regions of the Pt surface. These epitaxial BaTi O3 grains had (111) preferred orientation relative to the substrate su rface. Thus, the BaTiO3 films displayed bimodal growth behavior, with both (100) texture and (111) epitaxy. We propose a model for this beha vior based on surface energy considerations.