Engineering Oxide Epitaxy beyond Substrate Constraint.

Cheng, Mingqiang; Li, Changjian; Wang, Qiangli; Ding, Lingtong; Wang, Xiao; Zhong, Gaokuo; Li, Jiangyu · Nano Lett · 2024

basic_science · Level V

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Abstract

Orientation engineering is a crucial aspect of thin film growth, and it is rather challenging to engineer film epitaxy beyond the substrate constraint. Guided by density functional theory calculations, we use SrRuO<sub>3</sub> (SRO) as a buffer layer and successfully deposit [111]-oriented CoFe<sub>2</sub>O<sub>4</sub> (CFO) on [001]-, [110]-, and [111]-oriented SrTiO<sub>3</sub> (STO) substrates. This enables subsequent growth of [111]-oriented functional oxides, such as PbTiO<sub>3</sub> (PTO), overcoming the constraint of the substrate. This strategy is quite general and applicable to lanthanum aluminate and yttria-stabilized zirconia substrates as well. X-ray Φ scans and atomic resolution aberration-corrected scanning transmission electron microscopy (AC-STEM) reveal detailed epitaxial relations in each of the cases, with four variants of [111]-CFO found on [001]-STO and two variants found on [110]-STO, formed to mitigate the large lattice misfit strain between the film and substrate. Our strategy thus provides a general pathway for orientation engineering of oxide epitaxy beyond substrate constraint.