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N-doped ZnO films were prepared by annealing zinc oxynitride films deposited by rf reactive sputtering. Two Raman peaks were observed at 274 and 580 cm-1. According to the variation of the integral intensity of these two peaks, the nitrogen activation at 500 °C [the activation temperature (AT)] has been obtained. Below the AT, the integral intensities of them show a different variation trend. X-ray photoelectron spectroscopy (XPS) indicates the N chemical state variation for them and finds the activated Zn-N bond. Further analyses by photoluminescence (PL) spectra and spectroscopic ellipsometry (SE) have been carried out. The activated sample exhibits a symmetric emission peak at 3.22 eV assigned to be the A0X emission at room temperature. SE investigation takes account of samples within the different temperature span divided by the AT. Different factors, such as nitrogen dopant (N)O and the nanocrystal growth, which affect the redshift of the absorption edges, have been discussed. [ABSTRACT FROM AUTHOR]

The structural stability and optical properties of ultrathin HfAlOx films grown by facing-target reactive sputtering, depending on the postannealing temperature, have been determined via x-ray photoelectron spectroscopy and spectroscopic ellipsometry (SE). By virtue of the chemical shifts of Hf4f, Al2p, and Si2p core-level spectra, it has been found that the structural stability of HfAlOx/Si system sustains up to 800 °C. However, the breaking of the Hf–Al–O bond and the phase separation take place drastically at the annealing temperature of 900 °C. In particular, the information of an interfacial Si–O–Si bond as the dominant reaction during the postannealing treatment has been observed, confirmed by Fourier transform infrared spectroscopy. Analysis by SE, based on the Tauc-Lorentz model, has indicated that increase in the refractive index and reduction in thickness has been observed as a function of annealing temperature, originating from the annealing-induced higher packing density. The change of the complex dielectric functions and bandgap Eg correlated with the annealing temperature are discussed in detail. [ABSTRACT FROM AUTHOR]

Nanocrystalline ZnS has been synthesized using a sonochemical reaction of a mixed solution of Zn(NO3)2, Na2S2O3 and (CH3)2(OH)CH in Ar under ambient conditions. Detailed investigations with X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are reported. It was found that phase-pure ZnS nanocrystallites were produced, and the ZnS nanoparticles were about 6.5 nm in size, as indicated by TEM observation, The chemical mechanism for the formation of ZnS nanocrystals is discussed, This convenient method is found to he an efficient way to produce other chalcogenides as well. [ABSTRACT FROM AUTHOR]

Thermal stability and energy-band alignment of ZrOxNy films on Si are investigated using x-ray photoelectron spectroscopy and spectroscopy elliposometry (SE). The results show that the Zr–N bonds in as-oxidized ZrOxNy films are thermally unstable, while the N–O bonds in ZrOxNy matrix are stable even at high annealing temperature of 900 °C. Optical properties are also analyzed based on the SE fitting results. The slight blueshift in the absorption edge indicates the increased band gap from 3.9 to 5.1 eV after the additional annealing. Based on the valence-band spectrum results, zero-field energy-band alignments for ZrOxNy/Si and ZrOxNy/SiO2/Si stacks are extracted. [ABSTRACT FROM AUTHOR]

Large-scale synthesis of amorphous silica nanowires was achieved by using simple physical evaporation of a mixture of Si and Al2O3 powders. Scanning electron microscopy observations showed that the silica nanowires have lengths of several mm and diameters of 20-100 nm. X-ray photoelectron spectroscopy revealed that these nanowires consisted of Si and O elements in an atomic ratio of approximately 1:2, consistent with the stoichiometric formula SiO2. Photoluminescence measurements showed a blue luminescence band in the wavelength range of 400-500 nm with three peaks at 420 nm, 440 nm, and 470 nm, respectively, which also differs from the previous reports of the photoluminescence for oxygen-deficient silica nanowires. This may suggest that the fully oxidized silica nanowires still have many structural defects that contribute to the photoluminescence. [ABSTRACT FROM AUTHOR]