ABSTRACT
As nanotechnology continues to advance, the study of nanocomposites and their unique properties is at the forefront of research. There are still various blank spots in understanding the behavior of such composite materials, especially regarding plasmonic effects like localized surface plasmon resonance (LSPR) which is essential for developing advanced nanotechnologies. In this work, we explore the structural properties of composite thin films consisting of oxide matrices and gold nanoparticles (Au NPs), which were prepared by radio-frequency magnetron sputtering. Titanium dioxide (TiO2) and tungsten trioxide (WO3) were chosen as the host matrices of the composites. Such composite thin films owing to the presence of Au NPs demonstrate the LSPR phenomenon in the visible region. It is shown, that spectroscopic study, in particular, Raman spectroscopy can reveal peculiar features of structures of such composite systems due to LSPR and photoluminescence (PL) of Au NPs in the visible spectrum. In particular, defect peaks of TiO2 (700-720 cm-1) or WO3 (935 cm-1) in Raman spectra can be clearly observed when the samples are illuminated with a 633 nm excitation laser. Excitation with 532 nm leads to a decrease in the intensity of the defect peak, which totally disappears at 473 nm excitation. Such dependences of the defect peaks on excitation laser wavelength are probably related to the polarization of the matrix's defective regions close to the interface with gold NPs.
ABSTRACT
Zinc oxide is a promising multifunctional material. The practical use of nano- and polycrystalline ZnO devices faces a serious problem of instability of electrical and luminescent characteristics, due to the adsorption of oxygen by the surface during aging. In this paper, the aging effect in ZnO films and nanorod arrays was studied. It was found that ZnO samples demonstrate different behavior of the degradation process, which corresponds to at least two different types of adsorbing surface sites for O2, where O2 adsorption is of a different nature. The first type of surface sites is rapidly depassivated after hydrogen passivation and the aging effect takes place due to these centers. The second type of surface sites has a stable structure after hydrogen passivation and corresponds to HO-ZnO sites. The XPS components of these sites include the Zn2p3/2 peak at 1022.2 ± 0.2 eV and Zn2p1/2 peak at 1045.2 ± 0.2 eV, with a part of the XPS O1s peak at 531.5 ± 0.3 eV. The annealing transforms the first type of site into the second one, and the subsequent short-term plasma treatment in hydrogen results in steady passivation, where the degradation of characteristics is practically reduced to zero.
