Zinc oxide (ZnO) thin films annealed at different temperatures were studied with photoluminescence (PL), electrical resistivity, Hall mobility, and 1/f noise spectroscopy. Relatively high electrical conductivity and carrier concentration in sample annealed at 400 °C suggested the presence of ZnO interstitials. Rapid reduction in electrical conductivity and carrier concentration upon increasing the annealing temperature suggested that ZnO interstitials could be eliminated by high temperature annealing. Presence of G-R noise in sample annealed at 400 °C indicated high level of electron trapping activities. Density of Zn vacancies acting as electron traps was estimated by Lorentzian fitting on the G-R noise. PL spectra exhibiting dominant green emission in all samples suggested the presence of Zn vacancies in high concentration. Yellow-orange emission in PL in samples annealed at 600 °C and below indicated the presence of O interstitials, while the same emission in samples annealed at higher temperatures were ascribed to Si impurities diffused from the substrate. Sharp reduction in mobility and surge in Hooge’s parameter in sample annealed at 700 °C implied high level of electron scattering due to large extrinsic Si impurities. Gradual rise in green-yellow emission and electron concentration as annealing temperature increased from 500 to 700 °C were ascribed to the gradual formation of O vacancies.

Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) layers are used as the nucleation (seed) layer to reduce surface roughness of the overlying silver (Ag). The technique leads to ultrasmooth Ag thin films with a minimum surface roughness of 0.8 nm. The mechanism contributing to the improvement is explained on the basis of better wetting of Ag on PEDOT:PSS, and properties of the nucleation layer on the aspects of surface energy, surface adhesive force, and surface morphology influencing Ag wetting and growth pattern are being discussed. The surface plasmon resonance (SPR) shows significant improvement, in terms of the Figure of Merits (FOM), as the surface roughness on Ag films is reduced. A lower light scattering and longer plasmon propagation of maximum 15.3 μm are also realized on a smoother Ag surface. The results indicate great potential on the application of combined PEDOT:PSS/Ag structure as an effective and economically feasible design solution for plasmonic and optical metamaterials devices.

This paper demonstrates an optimized fabrication of amorphous Ru nanoparticles through annealing at various temperatures ranging from 150 to 700 °C, which are used as water oxidation catalyst for effective electrochemical water splitting under a low overpotential of less than 300 mV. The amorphous Ru nanoparticles with short-range ordered structure exhibit an optimal and stable electrocatalytic activity after annealing at 250 °C. Interestingly, a small quantity of such Ru nanoparticles in a thin film on fluorine-doped tin oxide glass is also effectively driven by a conventional crystalline silicon solar cell that has excellent capability for harvesting visible light. Remarkably, it achieves an overall solar-to-hydrogen efficiency of 11.3% in acidic electrolyte.