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Capturing the hidden short-range order in amorphous oxide interfaces that directs quasi-epitaxial thin-film growth

Kim, Junghwa1; Jeong, SeungGyo2; Kim, Whan Kyun2; Hwang, Soo-Yoon1; Kim, Kwangrak2; Jeong, Junho2; Park, Hansaem2; Kim, Wookrae2; Park, Jeong-Heon2; Lee, Myungjun2; Hyun, Sangjin2; LeBeau, James M.1

Published Oct 01, 2026 on Dryad. https://doi.org/10.5061/dryad.w9ghx3g61

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Abstract

As solid-state device architectures become increasingly complex, buried interfaces play a critical role in determining thin-film texture, morphology, and defect formation. However, resolving the structural features that control growth on nominally amorphous interlayers remains challenging because it requires three-dimensional sensitivity at high spatial resolution. Here, we combine four-dimensional scanning transmission electron microscopy, fluctuation electron microscopy, and multislice electron ptychography to investigate ruthenium (Ru) thin films grown on an underlying amorphous Ta2O5 layer, a material stack relevant for next-generation electronic and spintronic devices. Although the Ta2O5 layer appears amorphous in conventional imaging, from diffraction and depth-resolved ptychographic reconstructions, nanoscale β-Ta2O5-like ordered motifs are revealed near the Ru/Ta2O5 interface. These locally ordered motifs, together with the interfacial morphology, guide the orientation of the Ru layer and produce a textured, quasi-epitaxial film. The curved and atomically rough interface further induces depth-dependent strain gradients and promotes planar defect formation within the Ru layer. Collectively, these results demonstrate that hidden short-range order within nominally amorphous oxides can direct the growth of metallic thin films, providing a framework for engineering buried interfaces in advanced electronic and spintronic material stacks.