The optical properties of electrodeposited Zn-ZnO structures annealed at different temperature in oxygen ambient are studied. Zn and ZnO coexist in all samples measured by x-ray diffraction, but only ZnO is observed for a sample annealed at 800 °C. From photoluminescence analyses, green and orange-red emissions are observed from an as-prepared sample. The spectrum is almost the same for the sample annealed at 300 °C. It shows a strong ultraviolet (UV) emission at the wavelength of 374 nm for the annealing temperature of 500 °C; the UV emission redshifts to 384 nm for the annealing temperature of 800 °C. The existence of metallic Zn crystals in ZnO plays a significant role in the emission characteristics.

Metal–semiconductor Au–ZnO and Pt–ZnO films were prepared for enhancing ZnO photocatalytic activity. To increase the photocatalytic area in a metal–semiconductor material system, we introduce an efficient method where the metal and semiconductor are codeposited by an electrochemical method. The photocatalytic activity of Au–ZnO shows a better performance than that of Pt–ZnO determined by the degradation ability of methelene blue. There is an optimized Au concentration (∼2%) in Au–ZnO film for its best photocatalytic activity.

Both hexagonal zinc and wurtzite zinc oxide were deposited on p-type silicon substrate by the electrodeposition with an aqueous solution of zinc nitrate-6-hydrate near room temperature. Zinc dominates the growth at higher current density, and zinc oxide dominates the growth at higher deposition temperature. The optical emission from zinc and zinc oxide nanostructures are observed from microphotoluminescence spectra.Zinc oxide (ZnO) with wide direct band gap of 3.37 eV and high excitonic binding energy of 60 mV is a promising material for optoelectronic applications. It can perform ultraviolet (UV) emission at room temperature (RT). 1 Several reports indicate that ZnO has high photocatalytic efficiency. [2][3][4] The semiconductor-metal nanocomposites are expected to have higher potentials in catalysis, optics, and magnetic applications. [5][6][7] Recently, Zn-ZnO nanocomposites was obtained using ZnCl 2 electrolyte by the electrodeposition method at room temperature. 8 The electrodeposition method is an efficient way to prepare ZnO films at low temperature. 2 The shape and size of ZnO can be modulated by the cathodic potential, current density, 2 or adding molecular agents into the electrolyte. 3 On the other hand, the electrolyte of zinc nitrate-6-hydrate electrolyte used for Zn-ZnO nanocomposites formation can prevent Cl 2 contamination and meets the requirement of environmental protection. However, only ZnO was obtained at various deposition temperatures, 9 which could result from the lower applied current density. In this paper, a higher current density was used to prepare Zn-ZnO nanocomposites using zinc nitrate-6-hydrate electrolyte. The formation mechanism of Zn-ZnO nanocomposite and the role of Zn were also investigated.Several papers have been reported to prepare electrodeposited ZnO films at temperatures above 60°C on conductive electrodes, for example, indium tin oxide, 2,4 fluorine-doped tin oxide, 10 or n-type silicon 4 and gallium nitride 11 substrates. Boron-doped P-type (100) Si wafer with resistivity of 1-10 Ω-cm was used as the substrate in this experiment. The p-Si wafer is rarely used in electrodeposition, and we developed a simple way to deposit ZnO onto it. By this method, we can further build a structure of high quality n-ZnO on p-substrates to apply p-n junction devices. Otherwise, the heterojunction of n-ZnO and p-Si has the potential to separate the electron and hole and benefits the photocatalysis.Aluminum cathode was evaporated on the backside of the Si substrate. It was then coated with photoresist for the protection of the Al electrode during ZnO growth. A platinum sheet was used as the anode electrode. 0.1 M zinc nitrate-6-hydrate aqueous solution was used as the electrolyte. In order to investigate the function of current density (fixed at 0.1, 1, 10, and 20 mA/cm 2 ) for electrodepsited ZnO, the deposition temperature was fixed at 30°C. In order to investigate the function of deposition temperature (fixed at 30 and 65°C), the current density was fixed at 20 mA/cm 2 . T...

Pure ZnO was prepared at lower temperature (30 C) by electrodepositing at higher temperature (50 C), and Zn-incorporated ZnO was prepared. They were thermally treated in oxygen at different temperatures to investigate their optical characteristics using photoluminescence. The UV band from the band-edge emission is observed in the treated Zn incorporated ZnO but not in the thermally treated pure ZnO. The UV emission is proposed to be from the ZnO oxidized from Zn. The peak intensity of visible emission for the thermally treated Zn-incorporated ZnO is about 10 times that of emission from pure ZnO at 900 C. The blue-green band of visible emission results from the defects in ZnO oxidized from Zn and, its enhancement may be related to the thermal stress and the improvement of the interface between ZnO and ZnO oxidized from Zn.

The photoluminescence of porous silicon prepared by etching in an aqueous solution of hydrofluoric acid mixed with phosphoric and that with nitric acid were red and orange, respectively. The optical characteristics were stable under laser illumination or when stored in air for the aging test. For etching in an aqueous hydrofluoric acid/phosphoric acid electrolyte, the stability is attributed to the existence of Si-P and P-O-Si bonds formed on the porous silicon surface. For etching in an aqueous hydrofluoric acid/nitric acid electrolyte, it is attributed to more Si-O bonds formed on the porous silicon surface.