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Abstract Due to the unbalance between dielectric and insulation, the low dielectric constant and short corona aging life limit the application of the pure polyimide (PI). To achieve high dielectric constant and long corona aging life of polyimide-based composites simultaneously, the titanium oxide nanowires (TNWs) with high aspect ratio (20 nm in diameter, 10 μm in length and the aspect ratio is about 500) were reinforced into PI matrix by using in-situ polymerization in this study. The microstructure and electrical properties of PI/TNWs nanocomposite films with different mass fractions were investigated. The synchrotron radiation small angle X-ray scattering (SAXS) was carried out to explore how the interface structure affects the properties of PI/TNWs nanocomposite films. The results showed that the hybrid of TNWs not only make the structure of the composite films loose, but also increase the interfacial thickness of the PI matrix and TNWs. The dielectric constants of PI/TNWs nanocomposite films are increased dramatically up to 10.6 (about 3 times that of PI) with a only dielectric loss tangent of 0.03 at 101 Hz and the corona aging lifetime of 5 wt% PI/TNWs is closed to 28 h (about 9 times that of PI). In addition, the thermal stability of PI/TNWs nanocomposite films is also improved obviously. The resulted composites have a great potential application in the field of electrical insulation and electronic packaging. Highlights • TiO 2 nanowires (TNWs) with high aspect ratio was compounded into PI successfully. • The dielectric constant of PI/TNWs was up to 10.6 (about 3 times that of PI). • The Corona aging life of PI/TNWs reached to 28 h (about 9 times that of PI). • The thermal stabilities of PI/TNWs are obviously superior to that of PI. [ABSTRACT FROM AUTHOR]

Abstract: Ultrathin La2O3 gate dielectric films were prepared on Si substrate by ion assistant electron-beam evaporation. The growth processing, interfacial structure and electrical properties were investigated by various techniques. From XRD results, we found that the La2O3 films maintained the amorphous state up to a high annealing temperature of 900°C for 5min. From XPS results, we also discovered that the La atoms of the La2O3 films did not react with silicon substrate to form any La-compound at the interfacial layer. However, a SiO2 interfacial layer was formed by the diffusion of O atoms of the La2O3 films to the silicon substrate. From the atomic force microscopy image, we disclosed that the surface of the amorphous La2O3 film was very flat. Moreover, the La2O3 film showed a dielectric constant of 15.5 at 1MHz, and the leakage current density of the La2O3 film was 7.56×10−6 A/cm2 at a gate bias voltage of 1V. [Copyright &y& Elsevier]

Abstract: TiO2, which is high in refractive index and dielectric constant, plays an important role in the fields of optics and electronics. In this work, TiO2 films were prepared on glass substrates by the technique of ion beam assisted electron beam evaporation. The films were deposited at 50, 150 and 300°C, respectively. Then the as-deposited TiO2 films were annealed at 450°C for 1h in vacuum atmosphere. Structures and optical properties of TiO2 films were characterized by XRD, SEM, ellipsometry and spectrophotometer. As a result, the structure and the refractive index of films were improved by both the annealing and the increasing of the deposition temperature. The UV–vis transmittance spectra also confirmed that the deposition temperature has a significant effect on the transparency of the thin films. The highest transparency over the visible wavelength region of spectra was obtained at the deposition temperature of 300°C. The allowed direct band gap at the deposition temperature ranging from 50 to 300°C was estimated to be in the range from 3.81 to 3.92eV. [Copyright &y& Elsevier]