Facultatea de Fizică şi Inginerie / Faculty of Physics and Engineering

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Start date: 2015Subject: search.filters.subject.luminescence

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    Aero-TiO2 prepared on the basis of networks of ZnO tetrapods [Articol]
    (2022) Ciobanu, Vladimir; Ursachi, Veaceslav; Lehmann, Sebastian; Braniște, Tudor; Raevschi, Simion; Zamalai, Victor V.; Monaico, Eduard V.; Colpo, Pascal; Nielsch, Kornelius; Tighineanu, Ion
    In this paper, new aeromaterials are proposed on the basis of titania thin films deposited using atomic layer deposition (ALD) on a sacrificial network of ZnO microtetrapods. The technol-ogy consists of two technological steps applied after ALD, namely, thermal treatment at different temperatures and etching of the sacrificial template. Two procedures are applied for etching, one of which is wet etching in a citric acid aqua solution, while the other one is etching in a hydride vapor phase epitaxy (HVPE) system with HCl and hydrogen chemicals. The morphology, composition, and crystal structure of the produced aeromaterials are investigated depending on the temperature of annealing and the sequence of the technological steps. The performed photoluminescence analysis suggests that the developed aeromaterials are potential candidates for photocatalytic applications.
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    Photoluminescence study of Eu-doped Ga2O3 and GaN nanowires and nanoparticles produced by hydrothermal growth [Articol]
    (Editura "Tehnica-UTM", 2015-05-20) Rusu, Emil; Ursachi, Veaceslav; Culeac, Ion; Raevschi, Simion; Vlazan, Paulina
    We 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.
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    Photoluminescence properties of lamellar nano-composites obtained by Cd intercalation of GaSe and GaSe: Eu single crystals [Articol]
    (2015) Untila, Dumitru; Cantser, Valeriu; Caraman, Mihail; Evtodiev, Igor; Leontie, Liviu; Dmitroglo, Liliana
    In 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.
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    Magnetic and luminescent properties of nickel-doped ZnSe crystals [Articol]
    (Elsevier, 2015) Sirkeli, Vadim; Radevici, Ivan; Sushkevich, Konstantin; Nedeoglo, Natalia; Nedeoglo, Dmitrii
    Magnetic 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.%.