Nanocrystalline porous nitrogen doped titanium dioxide (TiO2) thin films were prepared by DC magnetron sputtering. Films were deposited in a plasma of argon, oxygen, and nitrogen, with varying nitrogen contents. The films were characterized by X-ray diffraction, scanning electron microscopy, and optical- and photoelectrochemical (PEC) measurements. These studies showed that the films were porous and displaying rough surfaces with sharp, protruding nodules having a crystal structure varying from rutile to anatase depending on the nitrogen content. All nitrogen doped films showed visible light absorption in the wavelength range from 400 to 535 nm. The PEC properties of the thin film electrodes were determined on as-deposited as well as dye-sensitized films. The nitrogen doped TiO2 generated an incident photon-to-current efficiency response in good agreement with the optical spectra. The PEC measurements on dye-sensitized films showed that the electron-transfer properties in the conduction band were similar to those of undoped TiO2. It was also experimentally confirmed that the states introduced by nitrogen lie close to the valence band edge. For the best nitrogen doped TiO2 electrodes, the photoinduced current due to visible light and at moderate bias was increased around 200 times compared to the behavior of pure TiO2 electrodes. There is an optimum in introduced nitrogen where the response is highest.

Electrical transport and optical properties were investigated in porous thin films consisting of In2O3:Sn (indium tin oxide, ITO) nanoparticles with an initial crystallite size of 16 nm and a narrow size distribution. Temperature dependent resistivity was measured in the 77<t<300 K temperature interval for samples annealed at a temperature in the 573tA1073 K range. Samples annealed at 573t A923 K exhibited a semiconducting behavior with a negative temperature coefficient of the resistivity (TCR). These data were successfully fitted to a fluctuation induced tunneling model, indicating that the samples comprised large conducting clusters of nanoparticles separated by insulating barriers. Samples annealed at tA = 1073 K displayed a metallic behavior with no signs of insulating barriers; then the TCR was positive at t> 130 K and negative at t<130 K. Effects of annealing on the ITO nanoparticles were investigated by analyzing the spectral optical reflectance and transmittance using effective medium theory and accounting for ionized impurity scattering. Annealing was found to increase both charge carrier concentration and mobility. The ITO nanoparticles were found to have a resistivity as low as 2 × 10-4 cm, which is comparable to the resistivity of dense high quality In2O3:Sn films. Particulate samples with a luminous transmittance exceeding 90% and a resistivity of 10-2 cm were obtained

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