The electronic and photoelectrochemical properties of the n‐type spinel oxides consisting of Zn‐Ti‐Fe are studied. The composition systems that give the single phase of the spinel structure are Znx2+Fe1−x3+false[Fe1−x2+Fe1+x3+false]O4 and Zn2+false[Zn0.5x2+Ti0.5x4+Fe2−x3+false]O4 . The conductivities of the former oxides are governed by the hopping mechanism between Fe2+ and Fe3+ at the octahedral site, while those of the latter oxides will be governed by normal band conduction. The difference between the Fermi level and the bottom energy of the conduction band is determined from the activation energies of the conductivity and the Seebeck coefficient. Photocurrents are observed for almost all the samples but disappear in the composition region at x<0.8 in the Znx2+Fe1−x3+false[Fe1−x2+Fe1+x3+false]O4 system. This is caused by the disappearance of the space charge layer developed by the high carrier density in the hopping level. The flatband potential and the bandgap depend on the cations in the octahedral site, but not on those in the tetrahedral site. The flatband potential shifts to positive and the bandgap decreases when Fe increases in the octahedral site. Zn2TiO4 is a useful anode material for the photoelectrolysis of water without bias, but it requires UV light. On the other hand, ZnFe2O4 has a relatively small bandgap and a little more negative flatband potential than that of a reversible hydrogen electrode, but its onset potential of the anodic photocurrent is more positive. The band structures of the spinel oxides used in this study are also discussed.

Langmuir-Blodgett (LB) multilayer thin films were fabricated from mixed monolayers containing stearic acid and various poly(3-alkylthiophenes). It has been found that mixed LB films containing as much as 80 mol % of poly(3-alkylthiophenes) form stable monolayers at the air-water interface that can be deposited onto solid substrates as Y-type films by the vertical lifting method. The LB films exhibit well-defined layered structures as determined by optical, capacitance, and X-ray diffraction measurements. Multilayer thin films containing highly ordered domains of cadmium stearate can be formed with polythiophenes substituted with alkyl chain lengths ranging from 4 to 18 carbon atoms. The molecular organization and the electrical and optical properties of the films depend on the length of the alkyl chain of the polythiophene backbone. All of these LB films can be rendered electrically conductive by doping with strong oxidizing agents. In some cases, conductivities as high as 2 S/cm were obtained via this doping process.

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