Facultatea de Fizică şi Inginerie / Faculty of Physics and Engineering
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Item Secondary ion mass spectroscopy of zinc selenide crystals with photoconductivity spectral memory [Articol](2017) Belenciuc, Alexandr; Ilinykh, Nicolai; Kovalev, LeonidItem Interface-controlled magnetism and transport of ultrathin manganite films [Articol](2013) Șapoval, Oleg; Huhn, Sebastian; Verbeeck, Johann; Jungbauer, Markus; Belenciuk, Alexandr; Moșneaga, VasiliiWe report ferromagnetic, T C ¼ 240 K, and metallic, T MI ¼ 250 K, behaviors of a three unit cell thick interface engineered lanthanum manganite film, grown by metalorganic aerosol deposition technique on SrTiO 3(100) substrates. Atomically resolved electron microscopy and chemical analysis show that ultrathin manganite films start to grow with La-O layer on a strongly Mn/Ti-intermixed interface, engineered by an additional deposition of 2 u.c. of Sr-Mn-O. Such interface engineering results in a hole-doped manganite layer and stabilizes ferromagnetism and metallic conductivity down to the thickness of d ¼ 3 u.c. The films with d ¼ 8 u.c. demonstrate a metallic conductivity down to the thickness of d ¼ 3 u.c. bulk-like transport behavior with TMI T C ¼ 310330 K.Item Development of materials for thermoelectric generators: superlattice Ca3Co4O9-Sr3cO4O9 [Articol](Editura "Tehnica-UTM", 2015-05-20) Șapoval, Oleg; Belenciuc, Alexandr; Jooss, Christian; Roddatis, Vladimir; Moșneaga, VasiliiWe have prepared multilayered structures composed from misfit layered Ca- and Sr- cobaltates by Metalorganic Aerosol Deposition technique. X-ray and Transmission Electron Microscopy analyzes confirms the forming superlattice along c direction from common CoO2 interlayers and alternating Ca2CoO3 and Sr2CoO3 layers with periodicity of 4-6 unit cell. Our results indicate the possibility to fabricate artificial material on the base of layered cobaltates for thermoelectric applications.Item Crystalline structure, surface morphology and optical properties of nanolamellar composites obtained by intercalation of InSe with Cd [Articol](2015) Untila, Dumitru; Caraman, Iuliana; Evtodiev, Igor; Canțer, Valeriu; Spalatu, Nicolae; Leontie, Liviu; Dmitroglo, Liliana; Luchian, EfimiaA material composed of InSe and CdSe crystallites was obtained by heat treatment at 753K of InSe single crystalline plates in Cd vapour for 3÷24 hours. The average diameters of CdSe and InSe crystallites determined from diffraction lines analysis are respectively equal to 20 nm and 22 nm. The photoluminescence spectra at 300K and 80K of composite decompose well into two Gaussian curves, one is in good correlation with the photoluminescence of CdSe crystals and the other is shifted to higher energies than the width of the band gap of CdSe crystals.Item Fotoluminescenţa straturilor nanolamelare de GaSe obţinute prin intercalarea cu Cd [Articol](2012) Dmitroglo, Liliana; Evtodiev, Igor; Caraman, Iuliana; Nedeff, Valentin; Dafinei, AdrianS-au analizat spectrele de emisie fotoluminescentă a lamelor monocristaline p-GaSe cu concentraţia golurilor3•1014 cm-3 şi a lamelor intercalate cu Cd în fază de vapori la temperatura 500 °C. Durata tratamentului termic a fost de 20 şi 24 ore. Spectrul de emisie al cristalelor de GaSe conţine liniile excitonilor direcţi localizaţi cu energia de legătură ~6 meV, prima repetare fononică a acestora (ħωf =20 meV) şi banda de emisie a excitonilor indirecţi cu emisia fononilor cu energia 15 meV. Spectrul de emisie a compozitelor obţinute prin intercalarea lamelor de GaSe cu Cd se obţine în rezultatul suprapunerii benzilor de emisie a compusului CdSe şi banda impuritară a monoseleniurii de galiu. Structura spectrului FL depinde de durata tratamentului termic. La majorarea timpului de tratament se amplifică subbanda corespunzătoare compusului CdSe.Item Effect of chlorine doping on CdTe thin films [Articol](2013) Dumitriu, Petru; Potlog, Tamara; Mîrzac, Alexandra; Dmitroglo, Liliana; Luca, DumitruThis paper analyzes the effect of chlorine treatment on the structure and resistance of CdTe layers. The morphology, chemical composition, and structure were studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD). Both non-activated and activated CdTe layers are polycrystalline with an average grain size being three times higher after chlorine activation and thermal treatment. All CdTe thin layers regardless of the treatment temperature have a cubic crystal structure.Item Photoelectrical parameters of ncds-pcdte thin film solar cells with CDO buffer layer [Articol](2016) Gașin, Petru; Gargara, Ludmila; Chetruș, Petru; Inculeț, Ion; Fiodorov, Vladimir; Qassem, Amjad-AlThe results of the studies of the effect of a CdO buffer layer on the photoelectrical parameters of CdS–CdTe solar cells have been described. It has been found that the formation of a 5–8 nm thick CdO buffer layer leads to an increase in the CdS–CdTe solar cell open circuit voltage (Voc) by 90–140 mV, short circuit current (Isc) by 1.4–3.2 mA/cm2, and efficiency by 2.8–4.1% at 300 K and an illumination of 100 mW/cm2.Item Influence of ZnS nanoparticles on productivity of red algae Porphyridium cruentum [Articol](Полиграфист, 2014-11-14) Goglidze, Tatiana; Dementiev, Igor; Guțul, Tatiana; Dvornicov, Dmitrii; Mironic, Tatiana; Rudi, Ludmila; Cepoi, LilianaНаночастицы ZnS были синтезированы с использованием коллоидных методов, Для получения водного коллоидного раствора, поверхность частиц была модифицирована тиоглицеролом. Наличие тиоглицерола на поверхности наночастиц было подтверждено с помощью инфра- красной спектроскопии. Водный раствор наночастиц ZnS был протестирован на красных водорослях Porphyridium cruentum, которые были использованы в качестве биологического объекта.Item Preparation and characterization of Ga2O3 and GaN nanoparticles [Articol](SPIE, 2015) Rusu, Emil; Ursachi, Veaceslav; Raevschi, Simion; Vlazan, PaulinaIn this communication, we present results on preparation of GaN nanoparticles by conversion of Ga 2O 3 nanocrystals in a flow of NH 3 and H 2. The monoclinic Ga2O 3 nanoparticles have been prepared by hydrothermal method with gallium nitrate and sodium hydroxide as precursors. Ga2O 3 nanowires are produced with increasing the duration of the hydrothermal process up to 24 hours. The production of β-phase Ga2O 3 has been confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. According to XRD, Raman and FTIR spectra, wurtzite type GaN nanocrystals with an average size of 28.6 nm are obtained by nitridation of Ga2O3 nanoparticles. Doping of Ga2O 3 nanomaterial with Eu 3+ ions in the hydrothermal process is demonstrated, and the emission spectra of this Eu-doped nanomaterial are compared with those of Eu-doped nanoparticles prepared previously by solid state reactions.Item 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, 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.