2. Articole
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Item MORPHOLOGY AND LUMINESCENCE PROPERTIES OF ZnO LAYERS PRODUCED BY MAGNETRON SPATTERING(Technical University of Moldova, 2011-07-07) Rusu, Emil; Ghițu, Irina; Prilepov, Vladimir; Zamalai, Victor; Ursachi, VeaceslavWe show that the morphology and the luminescence properties of ZnO layers produced by magnetron sputtering can be controlled by technological parameters of sputtering, particularly by the ratio of argon to oxygen gases in the gas flow during the growth process. Smooth and flat layers were produced with a high Ar/O ratio, while porous layers with various morphologies were obtained with a low Ar/O ratio. The layers produced with O/Ar ration equal to 10 exhibit extremely high near-bandgap luminescence intensity even higher in comparison with bulk ZnO single crystals. The free carrier density estimated from the analysis of photoluminescence spectra is also very high in these samples suggesting that these technological conditions promote both optical and electrical activation of the doping Al impurity. The samples grown with high Ar/O ratios exhibit strong visible emission which is controlled by the technological conditions.Item PHOTOLUMINESCENCE STUDY OF Eu-DOPED Ga2O3 AND GaN NANOWIRES AND NANOPARTICLES PRODUCED BY HYDROTHERMAL GROWTH(Editura "Tehnica-UTM", 2015-05-20) Rusu, Emil; Ursachi, Veaceslav; Culeac, Ion; Raevschi, Simion; Vlazan, PaulinaWe present results on preparation of Eu doped GaN nanoparticles and nanowires on the basis of Ga2O3 nanomaterial produced by hydrothermal growth. The monoclinic Ga2O3 nanoparticles and nanowires have been prepared with gallium nitrate and sodium hydroxide as precursors. nanomaterial produced by hydrothermal growth. The monoclinic Ga2O3 nanoparticles and nanowires have been prepared with gallium nitrate and sodium hydroxide as precursors. The geometrical form on the nanomaterial is determined by the duration of the hydrothermal process. The Ga2O3 nanomaterial is transformed unto GaN nanoparticles and nanowires by nitridation in a flow of NH3 and H2. The photoluminescence properties Eu doped Ga2O3 and GaN nanomaterial are investigated under pulsed and continuum wave excitation. The produced material is also investigated by means of XRD analysis, Raman scattering and Fourier transform infrared (FTIR) spectroscopy.Item PHOTOLUMINESCENCE PROPERTIES OF LAMELLAR NANO-COMPOSITES OBTAINED BY Cd INTERCALATION OF GaSe AND GaSe:Eu SINGLE CRYSTALS(2015) Untila, Dumitru; Cantser, Valeriu; Caraman, Mihail; Evtodiev, Igor; Leontie, Liviu; Dmitroglo, LilianaIn this work surface morphology, composition and photo- luminescence at 293 K and 78 K, of composite obtained by intercalation of GaSe and GaSe:Eu (0.49 at.% and 1.00 at.%) single crystal lamellas with Cd from vapor phase at 753 K and 830 K are investigated. As-obtained composite consists of CdSe and microstructured GaSe single crystallites. Photoluminescence spectrum of GaSe:Eu single crystal lamellas is composed of Eu3+ emission band 5 7 5 7 0 1 0 2( ,D F D FÆ Æ , and 5 7 1 3D FÆ transitions) and indirect exciton line in GaSe crystallites. Emission spectrum of single crystalline GaSe−CdSe composite, at 78 K and 293 K, consists of donor-acceptor band in GaSe microcrystallites and emission band of CdSe crystallites. Composite derived from the intercala- tion of GaSe:Eu (0.49 at.%) single crystals with Cd ex- hibits strong visible luminescence. Its quasi-continuous photoluminescence spectrum is produced by superposi- tion of luminescent emissions of CdSe nano- and mi- croparticles, and microstructured GaSe.Item THE STRUCTURE OF HIGH-TEMPERATURE BLUE LUMINESCENCE CENTERS IN ZINC SELENIDE AND MECHANISMS OF THIS LUMINESCENCE(Springer Nature, 1998) Ivanova, G.N.; Kasiyan, V.A.; Nedeoglo, Dmitrii; Nedeoglo, Natalia; Simashkevich, A.V.The characteristic features of temperature quenching of the intensity of the edge luminescence bands of n-ZnSe crystals annealed in different media (vacuum, Zn, Se) are investigated a wide temperature range. A change in the mechanisms of high-temperature exciton luminescence in the short-wavelength region of the spectrum (443 nm) with increase in temperature of the crystal is observed. It is shown that the nature of temperature quenching of the long-wavelength edge luminescence band (458 nm) is evidence of dissociation of associative luminescence centers with increase in the sample temperature.Item MAGNETIC AND LUMINESCENT PROPERTIES OF NICKEL-DOPED ZnSe CRYSTALS(Elsevier, 2015) Sirkeli, Vadim; Radevici, Ivan; Sushkevich, Konstantin; Nedeoglo, Natalia; Nedeoglo, DmitriiMagnetic and photoluminescent properties of nickel-doped ZnSe crystals with impurity concentrations varied by changing the Ni amount in the source material from 0.001 to 0.50 at.% are studied in 5–300 K temperature range. Investigation of magnetic properties shows that Ni impurity in ZnSe forms isolated paramagnetic centers and probability of Ni–Ni pairs formation is negligible due to low Ni concentration in the samples. The contribution of Ni impurity to edge emission and its influence on infra-red emission are discussed. It is found that complete concentration quenching of luminescence within all studied spectral range is observed starting with Ni concentration of 0.50 at.%.Item MAGNETIC AND LUMINESCENT PROPERTIES OF IRON-DOPED ZnSe CRYSTALS(Elsevier, 2010) Kulyuk, Leonid; Nedeoglo, Dmitrii; Nedeoglo, Natalia; Radevici, Ivan; Sirkeli, Vadim; Sushkevich, KonstantinMagnetic and luminescent properties of ZnSe crystals doped with Fe by various methods are studied. It is established that Fe impurity is responsible for photoluminescence (PL) bands at 980, 1320, 1450 nm and quenches PL band at 630–645 nm. It is found that magnetic properties of ZnSe:Fe crystals are sensitive to the doping method. At low fields, two magnetic subsystems may be observed for the samples doped with Fe during the growth process—weak paramagnetic subsystem and antiferromagnetic subsystem with TС=–130 K. For the samples doped with Fe by high-temperature annealing in Zn melt, few magnetic subsystems may be distinguished, however, the magnetic properties are typical for spin glasses with the transition temperature Tsg=(45–50) K.Item ЛЮМИНЕСЦЕНТНЫЕ ХАРАКТЕРИСТИКИ ТОНКИХ ПЛЁНОК ОКСИДА ЦИНКА, ПОЛУЧЕННЫХ МЕТОДОМ ЭЛЕКТРОФОРЕЗА(CEP USM, 2012) Гоглидзе, Т.И.; Дементьев, И.В.; Задорожный, А.П.; Коваль, А.В.; Петренко, П.А.; Гашин, П.А.Показана возможность осаждения тонких однородных слоёв оксида цинка с низкой проводимостью электрофоретическим методом. Представлены результаты измерений фотолюминесценции тонких слоёв ZnO при температурах 300 К и 77 К.