Materials Science Forum Vol. 1166

Abstract: Graphene oxide (GO) and reduced graphene oxide (rGO) were obtained from graphite foil wastes (GFWs) by oxidation with KMnO₄ in the presence of concentrated sulfuric acid at 25–50°C. The resulting GOs were compared with that obtained from flake graphite under the same conditions. The samples were investigated by UV–Vis, FTIR, and Raman spectroscopy methods. Spectroscopic data, as well as EDS and XRD analyses, have shown that the GO samples obtained in both cases are almost identical. The hydrodynamic diameter and ζ-potential of both sample suspensions were also determined. The average particles size of GO(graflex) is 321.5 nm, while the particles size of GO(graphite) reaches 252 nm. The measured ζ-potential values for GO(graflex) and GO(graphite) are –31.58 and –50.04 mV, respectively. Therefore, GFWs can serve as precursor for the production of GOs.

Abstract: The electronic structure of ultrathin Na/GaN interfaces was studied using photoelectron spectroscopy with synchrotron radiation in the photon energy range of 75–770 eV. The experiments were carried out in situ in ultrahigh vacuum of 5·10^–10 Torr with submonolayer sodium coverages on the gallium nitride surface. The photoemission spectra of the Ga 3d and N 1s core levels were studied at different excitation energies. It was found that Na adsorption causes a decrease in the intensity and a shift in the spectra of the Ga 3d and N 1s core levels towards higher binding energies. It was found that the sodium adsorption leads to some changes in the spectra due to charge transfer between the Na adlayer and the surface Ga or N atoms.

Abstract: Semiconductor nanostructures are referred to semiconductor heterostructures confined in one, two, or all three dimensions, which are known as quantum wells, quantum wires, and quantum dots (QDs), respectively. QDs are semiconductor nanocrystals with significant potential for high-performance photonic and electronic devices based on III–V semiconductor alloys. To fabricate these structures, several methods have been developed, including chemical synthesis of colloidal QDs, Stranski–Krastanov (S–K) growth technology, and droplet epitaxy (DE). DE is an epitaxial technique primarily employed for fabrication of nanostructures based on III–V semiconductors for quantum information technology applications. This work presents a DE technology of growth of InGaP nanocrystals on GaP surface. The technology includes the electrochemical deposition of group III metals on the III–V semiconductor surface, followed by annealing in inert gas atmosphere. The photoelectric and photonic properties of the resulting nanomaterials are analyzed. Based on the experimental results and literature data, the growth mechanism of InGaP nanocrystals on the GaP surface is described, and a phenomenological model for the formation of InGaP/GaP nanostructures is proposed.

Abstract: To understand the kinetics of changes in the majority current carriers Hall mobility temperature-dependency (in the temperature range of 77–300 K) in n- and p-type silicon crystals irradiated with high doses of high-energy particles during isochronous annealing, there are investigated P-doped n-Si samples irradiated with 25 MeV protons with dose of 8.1·10¹² cm^–2 at flux density of 1.5∙10¹¹ cm^–2·s^–1 and B-doped p-Si samples irradiated with 8 MeV electrons with dose of 1.0·10¹⁵ cm^–2 at flux density of 5.0·10¹² cm^–2·s^–1 at room temperature. Their isochronous annealing is performed in the temperature range of 80–500°C. The oscillatory character of the change in the majority current carriers Hall mobility in process of isochronous annealing of irradiated silicon samples is explained by the formation of disordered regions and the changes in degree of screening of their electric field potential barriers depending on charge states of nonequilibrium vacancies induced by irradiation.

Abstract: Paper investigates the possibility of producing silicon from silica contained in Shoda-Kedela (Oni-Gebi district, Georgia) quartz deposition. Characterization of silica from Shoda-Kedela quartz rock is carried by its crushing, grinding, thermal analysis, studying composition and density. Metallurgical grade silicon (MG-Si) is obtained by reducing Shoda-Kedela quartz in its reaction with coke in an electric arc furnace at temperature of ~1800°C. The obtained in this way material reveals that Shoda-Kedela silica containing of 99.58% SiO₂ would be useful for developing the silicon high-technology production.