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W-doped anatase TiO2 films were deposited on glass substrate by magnetron cosputtering. The minimum resistivity, 1.5×10-2 Ω cm, for Ti1-xWxO2 film (x=0.063) was obtained. X-ray photoelectron spectroscopy analysis shows W incorporated in the Ti lattice position is mostly in the W6+ state. Theoretical calculations based upon the density-functional theory were applied to analyze the electronic structure and conducting mechanism. The strong hybridization of Ti 3d states with W 5d states is the dominate factor to cause the shifting in Fermi level into conduction band. Our results suggest that tungsten is a favorable dopant to form TiO2-based transparent conducting oxide materials. [ABSTRACT FROM AUTHOR]

We report on the utilization of localized surface plasmon resonance (LSPR) of Ag nanoparticles to tailor the optical properties of VO2 thin film. Interaction of nano-Ag with incident light yields a salient absorption band in the visible-near IR region and modifies the spectrum of VO2 locally. The wavelength of modification occurs in a limited spectral region rather than affects the full spectrum. The wavelength of modification shows a strong dependence on the metal nanoparticle size and shifts toward the red as the particle size or the mass thickness of nano-Ag increases. Also, we found that the wavelength can be shifted into the IR further by introducing a thin layer of TiO2 onto the nano-Ag. Interestingly, with the help of LSPR effects the VO2 film exhibits an anomalous thermochromic behavior in the modification wavelength region, which may be useful in optical switching applications. [ABSTRACT FROM AUTHOR]

Thermal tuning of the localized surface plasmon resonance (LSPR) of Ag nanoparticles on a thermochromic thin film of VO2 was studied experimentally. The tuning is strongly temperature dependent and thermally reversible. The LSPR wavelength λSPR shifts to the blue with increasing temperature from 30 to 80 °C, and shifts back to the red as temperature decreases. A smart tuning is achievable on condition that the temperature is controlled in a stepwise manner. The tunable wavelength range depends on the particle size or the mass thickness of the metal nanoparticle film. Further, the tunability was found to be enhanced significantly when a layer of TiO2 was introduced to overcoat the Ag nanoparticles, yielding a marked sensitivity factor ΔλSPR/Δn, of as large as 480 nm per refractive index unit (n) at the semiconductor phase of VO2. [ABSTRACT FROM AUTHOR]

Abstract: Titanium dioxide (TiO2) of the anatase phase has recently attracted much attention as a novel transparent conducting oxide (TCO) due to its rich availability, high refractive index with low absorption in the solar spectrum. While it has been found that Nb is a dopant to obtain low resistivity (~10−4 Ωcm), other metals such as Ta, W etc., are also considered as potential effective dopants. In this paper, we carried out a parallel study on Nb- and Ta-doped TiO2 anatase films both theoretically by first principles calculation and experimentally by sputtering deposition and optical/electrical characterizations. The Nb-TiO2 films deposited on glass by co-sputtering at room temperature were amorphous, and the films crystallized into an anatase structure after vacuum-annealing, with the measured resistivity values comparative to the reported. The Ta-TiO2 films were deposited similarly, and the structure and properties were compared with the Nb-doped ones. Results showed that better performance was found in Nb-TiO2 films than that in Ta-TiO2 films. Theoretical calculations indicate that the larger lattice distortion by substitution of Ta for Ti is the dominating factor to suppress crystal growth and weaken the ability of electron mobility. [Copyright &y& Elsevier]