Dielectric Properties of Alkoxy-Derived BaTiO3 Films on LaNiO3/Pt/TiOx/Si(100)
BaTiO3 films with higher degrees of (100) orientation were deposited using both of the heterogeneous LaNiO3 nucleation layer and homogeneous BaTiO3 buffer layer. The microstructure and dielectric properties are characterized. The temperature dependence of the dielectric properties is additionally discussed. The alkoxy-derived 1-mum thick BaTiO3 had the unique microstructure and showed predominant (100) orientation. The film showed ferroelectric to paraelectric transition around at 105degC, and improved dielectric properties. The improvement is considered to be due to the simultaneous control of crystallographic and microstructural characteristics by using the double nucleation and buffer layers.
Thickness Dependence of Electrical Properties of Highly (100)-Oriented BaTiO3 Thin Films Prepared by One-Step Chemical Solution Deposition
Highly (100)-oriented BaTiO3 thin films having different thicknesses of 70–280 nm were deposited on Pt/TiOx/SiO2/Si substrates with LaNiO3 as a buffer layer by one-step chemical solution deposition. X-ray diffraction analyses showed that the LaNiO3 and BaTiO3 layers were all under tensile stress. The tensile stress of the LaNiO3 layer increased after depositing BaTiO3 films. The tensile stress in both the LaNiO3 and BaTiO3 layers decreased with increasing BaTiO3 layer thickness. The thickness dependences of the dielectric and piezoelectric behaviors of the highly (100)-oriented BaTiO3 films were investigated. It was found that the effect of tensile stress on the dielectric and piezoelectric properties is dominant. A reduction in in-plane tensile stress (primarily arising from a thermal expansion mismatch) was considered effective for increasing the dielectric and piezoelectric constants. The measured dielectric constant increased from about 313 for 70 nm films up to 831 for 280 nm films. The local effective piezoelectric coefficient increased from 15 pm/V for 70 nm films up to 45 pm/V for 280 nm films.
Preparation and Ferroelectric Properties of Ti-Site Substituted BaTiO3 Thin Films
Thin films of BaTi0.91(Hf0.5, Zr0.5)0.09O3 on Pt/SiO2/Si(100), Nb-doped SrTiO3 (100) and (111) substrates were synthesized by a pulsed laser deposition method using fourth harmonic generated light of Nd3+:YAG laser beam under low O2 partial pressure. The in-situ observation of BaTi0.91(Hf0.5, Zr0.5)0.09O3 film deposition on a Nb-doped SrTiO3 (100) substrate was performed using reflection high energy electron beam diffraction. The BaTi0.91(Hf0.5, Zr0.5)0.09O3 films deposited on Nb-doped SrTiO3 (100) and (111) substrates showed preferential [100] and [111] orientations, respectively. The ferroelectric properties of BaTi0.91(Hf0.5, Zr0.5)0.09O3 thin films were investigated by electrical measurements. The frequency dependence of the dielectric constant of BaTi0.91(Hf0.5, Zr0.5)0.09O3 thin film was influenced by low dielectric phase, and it was analyzed by the Debye model. The remanent polarization and coercive field of BaTi0.91(Hf0.5, Zr0.5)0.09O3 thin film were measured at room temperature, and those values were 7.4 µC/cm2 and 123 kV/cm, respectively.