13 research outputs found
NANO-OBJECTS IN OWN MATRIX - SELF COMPOSITE
No full textEstablishing the principles of nanoscience and nanotechnology has led to rethinking our understanding of the material\u27s properties. Therefore, some earlier results deserve to be analyzed again. In this paper, we present our results, which led to establishing a new type of nanocomposite - Self composite. The Self composite consists of matrix and nanometric size dispersed phase, with the specificity that the nano-object is formed from the same material or its parts, such as a matrix. We have made these nanocomposites using standard methods for the production of monocrystals or molecular beam epitaxy, but slightly above the solubility limit of the starting components. The possibility of obtaining Self composite by laser surface treatment of monocrystalline samples and agglomeration of a part of nanodimensional materials was also presented. Self composites are characterized (SEM, AFM, XRD, far-infrared, and Raman spectroscopy), and results were analyzed by Effective Medium Theory
Optical properties of CdS thin films
No full textThe properties of CdS thin films were investigated by applying atomic force microscopy (AFM), Raman and far-infrared spectroscopy. CdS thin films were prepared by using the thermal evaporation technique under base pressure 2 × 10−5 torr. The quality of these films was investigated by AFM spectroscopy. We applied Raman scattering and far-infrared spectroscopy to investigate the optical properties of CdS thin films, and reveal the existence of Surface Optical Phonon (SOP) mode at 297 cm−1. Effective permittivity of mixture was modeled by Maxwell–Garnet approximation. In the analysis of the far-infrared reflection spectra, a numerical model for calculating the reflectivity coefficient for a system which includes films and substrate was applied
Raman study of surface optical phonons in ZnO(Co) nanoparticles prepared by hydrothermal method
No full textOptical properties of plastically deformed copper: an ellipsometric study
No full textIn this paper the results of optical properties investigations on plastically deformed copper are presented. The optical properties of the plastically deformed copper were studied using spectroscopic ellipsometry in the ultraviolet-visible (UV-VIS) range. Chemically pure copper was deformed by applying the Equal Channel Angular Pressing (ECAP) technique. During the last decade, equal-channel angular pressing procedure was used for the fabrication of ultrafine-grained metals and alloys. The plastic deformation of metallic materials leads to the production of bulk nano-scale structures with ultrafine grains and cross-sections, which remain about equal before and after deformation. The parameters of the sample were calculated using a two-film model together with the Bruggeman effective medium approximation
Pb1-xMnxTe and PbTe1-xSx compounds and their optical properties
No full textPb1-xMnxTe crystals were obtained by the Bridgman method and PbTe1-xSx crystals were grown by the vapour–liquid–solid technique. The tructural properties of Pb1-xMnxTe (x £ 0.10) and PbTe1-xSx (x £ 0.05) were observed by X-ray powder diffraction analysis. The optical properties were studied by Raman spectroscopy as a function of temperature. Measurements on these samples of different composition gave information about the Mn and S position in the lattice (off-centering), their clustering and ordering, as well as of the influence of these processes on the crystal structure and properties. The model of phonon behaviour based on the Random Element Isodisplacement model was applied, and it was found that the phonons in PbTe1-xSx show a two-mode behaviour (each TO-LO mode pair of the end members degenerates to an impurity mode), while the Pb1-xMnxTe optical phonons have a ntermediate one-two-mode behaviour (the LO-mode frequency shifts continuously from PbTe to MnTe, while the other modes resemble the two-mode case)
Optical properties of CuSe thin films - band gap determination
No full textCopper selenide thin films of three different thicknesses have been prepared
by vacuum evaporation method on a glass substrate at room temperature. The
optical properties of the films were investigated by UV-VIS-NIR spectroscopy
and photoluminescence spectroscopy. Surface morphology was investigated by
field-emission scanning electron microscopy. Copper selenide exhibits both
direct and indirect transitions. The band gap for direct transition is found
to be ~2.7 eV and that for indirect transition it is ~1.70 eV.
Photoluminescence spectra of copper selenide thin films have also been
analyzed, which show emission peaks at 530, 550, and 760 nm. The latter
corresponds to indirect transition in investigated material.</jats:p
Phonons investigation of ZnO@ZnS core‐shell nanostructures with active layer
No full textIn the present work experimental study of the ZnO@ZnS core-shell nanostructure with an active layer obtained by conversion of zinc oxide powders with H2S is reported. Тhe prepared structures were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and far-infrared spectroscopy. Top surface optical phonon (TSO) in ZnO, characteristic for the cylindrical nano-objects, the surface optical phonon (SOP) mode of ZnS, and SOP modes in ZnO@ZnS core-shell nanostructure are registered. Local mode of oxygen in ZnS and gap mode of sulfur in ZnO are also registered. This result is due to the existence of an active layer in the space between ZnO core and ZnS shell, which is very important for the application of these materials as thermoelectrics. © 2020 John Wiley & Sons, Ltd
