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Nickel oxide (NiO) thin films were grown on glass substrate by direct current magnetron sputtering at different oxygen (O2) partial pressure. The influence of O2 partial pressure on the structural, optical, and electrochromic properties of NiO thin films were investigated. A strong relation between O2 partial pressure and NiO film properties such as optical transparency, crystallinity, grain size, lattice constant and the electrochromic properties was realized. The evaluation of the X-ray diffraction peaks indicated an increase with the in-plane lattice constant with the direction of (200) resulting in a strain on the NiO films. Both Ni2+ and Ni3+ were observed in NiO thin layers from X-ray photoelectron spectroscopy results and their concentration varied according to the O2 partial pressure. Optimization of O2 partial pressure led to reach the highest electrochromic efficiency of 53 cm2/C and optical transmittance variation of 51%. [ABSTRACT FROM AUTHOR]

We investigated the nonlinear and saturable absorption characteristics of very thin amorphous undoped GaSe, Ge (0.01 at. %), and Sn (0.5 at. %) doped GaSe films by pump-probe and open aperture Z-scan techniques. Linear absorption measurements indicate blueshift in energy with increasing film thickness. Thinner films exhibit saturable absorption while thicker films exhibit nonlinear absorption for 4 ns and 65 ps pulse durations. The films exhibit competing effects between nonlinear and saturable absorption. Saturable absorption behavior weakens while nonlinear absorption appears with increasing film thickness. In addition to that, saturable absorption behavior is very sensitive to doping. Doping causes absorption behaviors to appear in thinner films compared to undoped films. These behaviors are attributed to increasing localized defect states with increasing film thickness and doping. To derive the transmission in open aperture Z-scan data, a theoretical model incorporating one photon, two photon, and free carrier absorptions and their saturations were considered. The experimental curves were fitted to the theory of open aperture Gaussian beam Z-scan based on the Adomian decomposition method. Nonlinear absorption coefficients and saturation intensity thresholds were extracted from the fitting of the experimental results for both pulse durations used for the experiments. Saturation intensity threshold values increased with increasing film thickness and doping. The lowest saturation intensity threshold for undoped GaSe film was found to be 1.9×10-3 GW/cm2 for 45 nm film thickness and increased about two orders of magnitude for 74 nm film thickness. [ABSTRACT FROM AUTHOR]

Al3+ is considered as one of the alternative charge carrier ions to Li+ for WO 3 based electrochromic (EC) devices. In this study, WO 3 films have been grown by Magnetron Sputtering method and tested in Li+ and Al3+ liquid electrolytes for the comparison of EC performances. In order to see the effects of structure and heat treatment on the EC performance of WO 3 films in both liquid electrolytes, films were annealed at 250°C, 350°C and 450°C. As deposited film and films heat treated up to 350°C were amorphous while the film annealed at 450°C crystallized. Surface modifications were observed with annealing, especially for the film annealed at 450 °C. X-ray photoelectron spectroscopic analysis indicated that the binding energies of W 4f did not vary much with annealing. However, noticeable changes were observed after the EC test performed on the WO 3 films in trivalent Al3+ compared to the films tested in monovalent Li+ liquid electrolyte. The optic transmittance of the pristine and annealed films was basically the same except the film annealed at 450 °C for which the transmittance decreased by 25%. The Li+ ions have higher insertion and extraction in and out of the annealed films except the film annealed at 450 °C. The optical modulation parameter was highest for the film annealed at 350 °C tested in Al3+ while that of the pristine film was the highest for the films tested in Li+ electrolyte. The diffusion coefficients of Al3+ ions is calculated to be smaller compared to Li+ ions. The WO 3 film annealed at 350 °C was found to be the most durable when tested in Al3+ while both pristine and heat-treated films had relatively better long-time durability for the cycle times used. • WO 3 films were grown by DC Magnetron Sputtering. • Effect of heat treatment and type of liquid electrolyte were investigated. • The coloration efficiency decreases but films become more stable with heat treatment. • The EC performance of the film is better in general for Li+ liquid electrolyte compared to the Al3+. [ABSTRACT FROM AUTHOR]

• WO 3 :Al films (0.7–4.3 at%) were prepared by RF Magnetron Sputtering. • W ions exist in the 6+ valence. • Al doping did not adversely affect the transparency of WO 3 films. • 1.5% Al doped WO 3 sample showed the highest optical modulation of 44%. Effect of Al doping on the structural, optic, and electrochromic properties of tungsten trioxide (WO 3) thin films was investigated through X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, optic transmittance, spectral ellipsometry, cyclic voltammetry and chronoamperometry measurements. Undoped and 0.7–4.3% Al doped WO 3 films were grown by radio frequency magnetron sputtering. All of the WO 3 :Al films investigated grew in amorphous phase. The thicknesses of the films varied between 113 and 124 nm. X-ray photoelectron spectroscopy analysis indicated that tungsten atoms exist as W6+ in both undoped and Al doped WO 3 films. The optical transmittance of WO 3 films is not affected by the Al doping. Their transparency in the visible range is around 90% while the transmittance in the near infrared region seems to slightly increase (around 5%) with increasing Al doping. The optical band gap energies increase with Al doping concentrations exceeding 1.5%. Variation of the coloration / bleaching times and coloration efficiency of the WO 3 films with Al doping was analyzed. The highest optical modulation of 44% was obtained for 1.5% Al doped WO 3 film at 630 nm. [ABSTRACT FROM AUTHOR]