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We have proposed that BiFeO3 films are suitable for piezoelectric vibrational energy harvester (VEH) applications, because BiFeO3 has high spontaneous polarization and low dielectric permittivity. We demonstrated that energy can be harvested by a micromachined VEH using a BiFeO3 film deposited using a sol–gel process. A VEH with a resonant frequency of ∼98 Hz produced an output voltage of 1.5 V·G-1 and electrical power of 2.8 µW·mm-3·G-2 (G=9.8 m/s2) at a load resistance of 1 MΩ. Using the analytical model for VEH, the generalized electromechanical coupling factor was estimated to be 0.41%. These results were comparable to those of the best-performing VEHs using other piezoelectric films.

Zinc stannate (Zn2SnO4) thin films were deposited by RF magnetron sputtering on silica substrates at various [O2/(Ar+O2)] flow ratios. The influences of the [O2/(Ar+O2)] flow ratio on the crystalline structure, and the optical and electrical properties have been investigated. No sharp X-ray diffraction (XRD) peaks were observed in as-deposited thin films. After postdeposition annealing in air at 750°C, the thin films showed a preferred orientation of (111). The thin films exhibited a high transmittance in the visible spectrum irrespective of the [O2/(Ar+O2)] flow ratio or postdeposition annealing. The optical band gap was estimated to be 4.1 eV by analyzing the optical spectra of thin films annealed at 750°C. The composition ratio of Zn/Sn for thin films deposited in an Ar/O2 mixture was 2.0 and their electrical resistivity was on the order of 105 Ω·cm. In contrast, the composition ratio of Zn/Sn for a thin film deposited in pure Ar was 1.5 and an electrical resistivity of 4.1 ×10-2 Ω·cm was observed.

The preparation of organic–inorganic hybrid gate dielectrics of poly(methyl silsesquioxane) (PMSQ) at a low processing temperature has been studied for use in organic field-effect transistors (OFETs) by the solution process. It is found that the electrical resistivity of a PMSQ film synthesized by a sol–gel method is significantly influenced by the synthesis conditions such as the type of organic solvent used and water content. PMSQ films prepared in toluene show a high resistivity of over 1014 Ω cm even at a low thermal treatment of 150 °C, which is attributed to the decrease in the silanol concentration of the PMSQ films. Top-contact OFET fabricated on a PMSQ-coated SiO2 gate dielectric using poly(3-hexylthiophene) exhibits mobility improvement similarly to devices with self-assembled monolayer-modified SiO2 dielectrics.