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.
SEASONAL AND REGIONAL MPG AS INFLUENCED BY ENVIRONMENTAL CONDITIONS AND TRAVEL PATTERNS
In-use fuel economy shortfall varies regionally and seasonally in response to changing environmental conditions and travel patterns. Shortfall changes by 25 percent or more are associated with variation in miles travelled per day by in-use vehicles. Monthly variations in northern states are twice those in the south; air conditioning penalties also vary by region. Although regional difference in annual levels are relatively small, shortfall can increase by 16 percent in densely populated urban areas. These variations have been quantified in an analysis of time-series mpg data and related to variables commonly reported in fuel economy surveys.