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.
Dielectric Properties of BaTiO3 Thin Films Derived from Clear Emulsion of Well-Dispersed Nanosized BaTiO3 Particles
The dielectric properties of thin films with microemulsion (ME)-routed nanocrystalline BaTiO3 particles were investigated in terms of the films' crystallinity and grain size. The ME method provided a clear emulsion of well-dispersed nanocrystalline BaTiO3 particles. BaTiO3 thin films were prepared by direct spin-coating of the clear emulsion on Si/SiO2/Al2O3/Pt substrates. By varying the postannealing temperature from 600°C to 1000°C, BaTiO3 thin films of different grain sizes were prepared. A fine BaTiO3 powder was removed from the clear emulsion by adding ammonia solution to cause flocculation, followed by centrifugation and washing. A transmission electron microscope (TEM) observation revealed that the powder generated many inner voids, but the thin films did not contain inner voids, thus resulting in high crystallinity. The dielectric properties of these films were measured as functions of temperature. Polarization as a function of voltage was measured, and a ferroelectric D-E hysteresis curve was observed in the sample with a mean grain size of 18 nm. The measurement of piezoelectric hysteresis using a scanning probe microscope (SPM) also revealed ferroelectricity in a small area just below the SPM probe. Direct use of the clear emulsion of well-dispersed nanocrystalline BaTiO3 particles in the ME method enables the fabrication of BaTiO3 thin films that consist of nanocrystalline BaTiO3 grains without inner voids, and the films exhibit great dielectric performance.
Effects of Bottom Electrode on the Structural and Electrical Characteristics of Barium Titanate Thin Films
Barium titanate thin films of 50 nm thickness and having a composition of Ba(Zr0.12Ti0.88)O3 (BZT) were deposited on different electrodes of LaNiO3 (LNO), Pt and RuO2 by rf magnetron sputtering at 400°C. Highly crystallized and (100)-oriented BZT films were formed by deposition on the (100)-textured LNO electrode, but poorly crystallized films were obtained by deposition on the other two electrodes. The films deposited on LNO were smooth and had a flat interface that epitaxially bonded with the LNO electrode. However, the films deposited on Pt or RuO2 were rough and had a rugged film/electrode interface. High interdiffusion was found at the BZT/RuO2 interface, but not at the other two interfaces. The dielectric constant of the film on LNO was ∼250, but that of the films on Pt or RuO2 was ∼120. For the former, a high and stable insulating characteristic against biasing voltage was also found, i.e., a low leakage current of 10-9 A/cm2 was maintained before reaching a high onset voltage of 5 V. In contrast, the leakage current rapidly increased to >10-7 A/cm2 with increasing bias to 5 V or 2 V for the films deposited on Pt or RuO2, respectively. The relationship of current versus time (J–t) measured at 380 K also revealed the superior insulating property of the film deposited on LNO compared to the other two films.