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Page 4 of 10 Ouyang et al. Microstructures 2023;3:2023027 https://dx.doi.org/10.20517/microstructures.2023.22

Table 1. Magnetron sputtering parameters of BaTiO film heterostructures
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Structure type BaTiO /Pt/Ti BaTiO /LaNiO /Pt/Ti
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-4
-4
Base pressure 2 × 10 Pa 2 × 10 Pa
Pt/Ti layer sputtering pressure 0.3 Pa 0.3 Pa
Pt/Ti layer thickness ~150-200 nm
Buffer layer sputtering temperature N/A 500 °C
Buffer layer sputtering atmosphere N/A Ar:O (4:1)
2
Buffer layer sputtering pressure N/A 0.3 Pa
Buffer layer thickness N/A ~100 nm
BaTiO sputtering temperature 500 °C 500 °C
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BaTiO sputtering atmosphere Ar:O (4:1) Ar:O (4:1)
3 2 2
BaTiO sputtering pressure 0.3 Pa 1.2 Pa
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BaTiO deposition rate ~7 nm/min ~10 nm/min
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BaTiO layer thickness (nm) 435 nm, 845 nm, 1,305 nm, 2,610 nm 510 nm
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Cooling atmosphere (pressure) Pure O (2.5 Pa) Pure O (2.5 Pa)
2 2

Figure 1. XRD θ-2θ scan patterns of the thin film heterostructures of (A) BaTiO /Pt/Ti/Si (with various thicknesses of the BaTiO layer)
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and (B) BaTiO /LaNiO /Pt/Ti/Si (with a 510 nm thick BaTiO layer).
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improved in the thicker polycrystalline BaTiO film, as evidenced by their stronger and sharper diffraction
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peaks. The preferred crystalline orientation, which was (110) in the 435 nm thick film, changed into (111) in
the 845 nm and 1,305 nm thick films and finally became (001) in the 2,610 nm thick film. The degree of
grain (00l)-orientation of unbuffered BaTiO film was evaluated using the Lotgering factor F = 64.7%
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(00l)
[Figure 1A] and compared with those of the standard powder XRD pattern of BaTiO (JCPDS 05-0626).
[16]
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The growth of BaTiO on (111) Pt involves a competition between various factors, including the channeling
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effect , interface energy, and surface energy. The dominance of the channeling effect is evident in the
[17]
thinnest film, leading to a preferred orientation of the closest-packed plane of (110) in perovskite. As the
film thickness increases, the interface energy, primarily influenced by misfit strain energy, becomes more
significant. This leads to the (111) orientation, which is the best match to the (111) Pt base plane, taking
over as the preferred crystalline orientation. Lastly, in the thickest film where the residual misfit approached
zero, (001) crystalline planes with the minimum surface energy emerged as the preferred orientation. On
the other hand, in the LaNiO -buffered BaTiO film, since the (100)-textured growth of LaNiO on Pt has
[18]
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been preset, the (001) orientation of the BaTiO film satisfies the requirement of minimum energy, which is
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now dominated by the interface/surface energy term. The Lotgering factor F for buffered BaTiO film is
(00l)
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