2. Articole
Permanent URI for this collectionhttps://msuir.usm.md/handle/123456789/47
Browse
7 results
Search Results
Item LUMINESCENT PROPERTIES OF Sb-DOPED ZnSe SINGLE CRYSTALS(2019) Sushkevich, Konstantin; Goncearenco, Evghenii; Nedeoglo, Natalia; Nedeoglo, DmitriiPhotoluminescence (PL) spectra of ZnSe:0.1at%Sb single crystals are studied between 90 and 300 K. The samples are grown by the chemical vapor transport (CVT) method with iodine as a transport agent and doped with Sb impurity during the growth. A yellow PL band with a maximum at 2.16 eV (575 nm) at room temperature is observed for the first time. A model of a (SbSeISe) acceptor center with the energy level located at 0.52 eV above the valence band edge is proposed, and the mechanism of the formation of this yellow PL band under direct and indirect excitation is discussed.Item INFRARED PHOTOLUMINESCENCE OF ZnSe:GD CRYSTALS(Elsevier, 2015) Colibaba, Gleb; Goncearenco, Evghenii; Nedeoglo, Dmitrii; Nedeoglo, NataliaPhotoluminescent and optical properties of ZnSe crystals doped with Gd impurity are investigated in infrared (IR) spectral range. The influence of crystal growth temperature, impurity concentration, stoichiometric deviation and post-annealing cooling rate, concentration of Cr and Cu background impurities, temperature and excitation level on photoluminescent and optical properties of the samples is studied. Based on these investigations, the structure of complex IR photoluminescence (PL) bands is analyzed. Correlation between the component parts of the bands at 1 and 2 µm is found and possibility to control the IR PL spectra by enrichment of the samples with Zn or Se is discussed. Coincidence of the IR PL spectra structure is shown for the samples doped with Gd, Yb, and Cr impurities. The model that explains the formation of complexes based on rare-earth elements (REEs) and Cr and Cu background impurities fixed in the nodes of crystal lattice with tetrahedral symmetry, responsible for IR PL bands, is proposed.Item PHOTOLUMINESCENCE OF ZnSe SAMPLES DOPED WITH ANTIMONY AND IODINE(Elsevier, 2021) Sushkevich, Konstantin; Goncearenco, Evghenii; Nedeoglo, Natalia; Nedeoglo, DmitriiPhotoluminescence (PL) spectra of ZnSe samples grown by Chemical Vapour Transport (CVT), Physical Vapour Transport (PVT), and from melt have been studied in the temperature range from 100 to 300 K. Impurity-defect composition of the studied samples was varied by doping with antimony (Sb) or iodine (I), as well as co-doping with Sb and I, both during the crystal growth and crystal annealing in the respective melts. It is established that the PL band with maximum at (570–580) nm is present only in the spectra for ZnSe samples co-doped with Sb and I, independent of growth technique mand doping method. The (SbSe–ISe) radiative centre, with the energy level placed 0.5 eV above the valence band top, is proposed to be responsible for this PL band.Item PHOTOLUMINESCENCE STUDY OF ZnO NANOSTRUCTURES GROWN ON SILICON BY MOCVD(Elsevier, 2012) Sirkeli, Vadim; Nedeoglo, DmitriiZnO nanostructures with a size ranging from 20 to 100 nm were successfully deposited on (1 0 0)-Si substrates at different temperatures (500–800 °C) using MOCVD. It could be confirmed that the size of ZnO nanostructures decreased with increasing growth temperature. From photoluminescence (PL) studies it was found, that intensive band-edge PL of ZnO nanostructures consists of emission lines with maxima at 368.6 nm, 370.1 nm, 373.7 nm, 383.9 nm, 391.7 nm, 400.7 nm and 412 nm. These lines can be dedicated to free excitons and impurity donor-bound excitons, where hydrogen acts as donor impurity with an activation energy of about 65 meV. A UV shift of the band-edge PL line with increasing growth temperature of ZnO nanostructures was observed as a result of the quantum confinement effect. The results suggest that an increase of growth temperature leads to increased band-edge PL intensity. Moreover, the ratio of band-edge PL intensity to green- (red-) band intensity also increases, indicating better crystalline quality of ZnO nanostructures with increasing growth temperature.Item SHALLOW DONOR STATES INDUCED IN ZNSE:AU SINGLE CRYSTALS BY LATTICE DEFORMATION(American Institute of Physics, 2008) Nedeoglo, Natalia; Nedeoglo, Dmitrii; Laiho, R.; Sirkeli, Vadim; Lähderanta, E.Photoluminescence (PL) spectra are investigated in n-ZnSe single crystals at different temperatures from 4.4 to 300 K immediately after doping with Au from melt of Se+Au or Zn+Au and after storage of the doped samples for 4 years in the dark under normal room conditions. Due to the formation of Aui interstitial donors in the n-ZnSe:Se:Au crystals with time, the origin of the near band edge PL changes from acceptor-bound to donor-bound excitons. Taking into account the results of PL characterization, we proposed that the Aui donors are generated by displacement of Au ions from regular lattice sites to interstitial sites with the help of lattice deformation forces. Transport measurements show dramatic increase in the electrical conductivity and the free electron concentration after storage of the n-ZnSe:Zn:Au crystals, thus confirming the proposed model.Item LUMINESCENT PROPERTIES OF ZnO POWDERS SYNTHESIZED BY THE ISOVALENT SUBSTITUTION METHOD(2016) Goglidze, Tatiana; Dementiev, Igor; Koval, Andrei; Nedeoglo, Natalia; Nedeoglo, DmitriiZinc oxide powders have been prepared by the isovalent substitution method by means of high - temperature annealing of a zinc sulfide powder synthesized by a chemical method. Investigation of photoluminescence (PL) spectra in dependence on annealing temperat ure varied from 870 to 1050 С has made it possible to find the temperature range of 920 – 950 С for the most active isovalent substitution of oxygen atoms for sulfur atoms and the formation of a ZnO S phase. X - ray diffraction analysis has revealed that the p owder with crystal lattice parameters а о = 0.3249 nm and с о = 0.5206 nm and the ratio of с о / а о = 1.60, which are characteristic of zinc oxide crystals, is synthesized at the maximum annealing temperature. It has been found that the maximum of a structurel ess PL band in the spectrum for the ZnO powder at room temperature is localized at 500 nm. It has been supposed that the band is caused by ―free electron – acceptor‖ radiative transitions, where the acceptor level is 0.95 eV above the valence band edge.Item EFFECT OF ANNEALING OF ZnSe:Cr CRYSTALS IN Bi(Zn) MELT ON THE INTENSITY OF RADIATION BANDS OF Cr IONS(2010) Kulyuk, Leonid; Nedeoglo, Dmitrii; Siminel, Anatolii; Sushkevich, ConstantinThe photoluminescence in visible and near-IR spectral range of ZnSe:Cr as-grown and annealed in Bi(Zn) melt crystals was investigaded at room temperature. It was established that heat treatment of the crystals in Bi melt does not lead to chrome extraction, but their annealing in Zn melt results in partial extraction into melt of chrome and some other shallow impurities.