Electrical properties of (1 0 0)-predominant BaTiO3 films derived from alkoxide solutions of two concentrations

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.