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Ouyang et al. Microstructures 2023;3:2023027 https://dx.doi.org/10.20517/microstructures.2023.22 Page 5 of 10

Figure 2. AFM surface scan images of (A) the 435 nm thick BaTiO film grown on Pt/Ti/Si and (B) the 510 nm thick BaTiO film grown
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on LaNiO /Pt/Ti/Si.
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Figure 3. Cross-sectional TEM images of (A) the BaTiO (435 nm) /Pt/Ti/Si and (B) the BaTiO (510 nm)/LaNiO /Pt/Ti/Si
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heterostructures.
87% [Figure 1B].

According to the study by Zhang et al., the relative dielectric permittivity of a polycrystalline BaTiO film
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[19]
deposited on a Pt electrode is expected to be higher than that of the (001)-textured film. Moreover, the
presence of larger grain sizes in the thicker films warrants an improved dielectric response, which can be
[20]
attributed to extrinsic sources such as domain wall movements and grain re-orientations. Next, we will
compare their nanostructure characteristics, including grain and interface morphologies, of the 510 nm
thick buffered and the 435 nm thick unbuffered BaTiO film samples to complement the XRD results.
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Figure 2A and B displays the surface AFM image of the two films. Both films showed a dense and granular
surface, with a root mean square roughness (Ra) of 2.868 (A) and 2.007 nm (B), respectively.
Figure 3A and B presents the cross-sectional TEM image of the two BaTiO films. The unbuffered film
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consists of discontinuous columnar nanograins, occasionally displaying twisted or canted orientations. In
contrast, the bi-layer film of BaTiO /LaNiO constitutes continuous arrays of columnar nanograins that
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extend from the LaNiO /Pt bottom electrode interface to the surface of the BaTiO layer. These
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