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.
Electrical properties of (100)-predominant BaTiO3 films derived from alkoxide solutions of two concentrations
Abstract Lead-free piezoelectric films with thickness larger than 1 μm integrated on silicon substrates have been receiving considerable attention because of environmental concerns and their potential applications in microelectromechanical systems. We demonstrate that, by chemical solution deposition, it is possible to process (1 0 0)-predominant 1 μm BaTiO3 films on LaNiO3/Pt/TiOx/SiO2/Si substrates using thinner high-crystallinity columnar BaTiO3 films as buffer layers. We point out that this kind of buffer layer prepared with a lower concentration solution on the surface of an LaNiO3/Pt electrode is effective in enhancing the crystallinity and orientation degree of final BaTiO3 films prepared with a higher concentration solution. The 1 μm BaTiO3 films show good dielectric and insulating characteristics against an applied field, and the conduction current shows Schottky emission behavior at modest voltage and space-charge-limited behavior at higher voltage. We also demonstrate that the (1 0 0)-predominant 1 μm BaTiO3 films have excellent piezoelectric properties: piezoelectric coefficients d33 higher than 50 pm/V have been determined for the bare films using atomic force microscopy, which are comparable to those of Pb(Zr,Ti)O3 films. These results indicate that the (1 0 0)-predominant BaTiO3 films should be promising candidates for microelectromechanical systems applications.
Synthesis of BaTiO3 Thin Films Substituted with Hafnium and Zirconium by a Laser Ablation Method Using the Fourth-harmonic Wave of a YAG Laser
For the first time to our knowledge, BaTi(Hf0.5Zr0.5)O3 (BTHZ) thin films have been successfully synthesized using a laser ablation technique that employs the fourth harmonic wave of a pulsed YAG (FHG-YAG) laser. The BTHZ thin film with a preferred orientation in the c-axis was prepared under an oxygen gas pressure of 3 Pa at 800° C. Chemical bonds in the BTHZ compounds can easily be broken by irradiation at an optical energy of 7.47×10-19 J and an optical power density of 300 mJ/cm2. Crystallinity of the deposited films is dominated by the mean free path of each element.