Orientation control of barium titanate films using metal oxide nanosheet layer

In the present work, we aim to achieve the preferred crystal orientation of chemical solution deposition (CSD)-derived BaTiO3 films on ubiquitous Si wafers with the assistance of Ca₂Nb₃O₁₀ nanosheet (ns-CN) template layers. The ns-CN on platinized Si (Pt/Si) substrates aligned the BaTiO₃(100) plane to the substrate surface, because of the favorable lattice matching of the ns-CN (001) plane. The CSD process in air required a high crystallization temperature of 900 °C for the preferred crystal orientation of BaTiO3₃(100) because of the BaCO₃ byproduct generated during the combustion reaction of the precursor gel. The processing in vacuum to remove CO₂ species enhanced the crystal orientation even at the crystallization temperature of 800 °C, although it can generate oxygen vacancies (VO) that cause distorted polarization behavior under an applied field higher than approximately 150 kV/cm. The relative dielectric constant (ϵr) of the (100)-oriented BaTiO₃ film on the ns-CN-supported Pt/Si substrate (ns-CN/Pt/Si) was generally larger than that of the randomly oriented film on Pt/Si, depending on the degree of crystal orientation.