2. Articole
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Item SECONDARY ION MASS SPECTROSCOPY OF ZINC SELENIDE CRYSTALS WITH PHOTOCONDUCTIVITY SPECTRAL MEMORY(2017) Belenciuc, Alexandr; Ilinykh, Nicolai; Kovalev, LeonidItem INTERFACE-CONTROLLED MAGNETISM AND TRANSPORT OF ULTRATHIN MANGANITE FILMS(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 MAGNETOTRANSPORT PROPERTIES OF ULTRATHIN LaMnO3 LAYERS(Technical University of Moldova, 2011-07-07) Șapoval, Oleg; Belenciuc, Alexandr; Zasavițchi, Efim; Canțer, Valeriu; Moșneaga, VasiliiWe report the transport and magnetic properties of La-deficient ultrathin films of La1-MnO3 (LMO) grown on SrTiO3 (STO) and engineered by using different interfacial layers. LMO layer and adjusting interface oxide (LaO-STO and SMO) layers were grown by a metalorganic aerosol deposition technique with monolayer accuracy. The role of LaO-TiO2 interface in the formation of ferromagnetic metallic state in very thin LMO films was demonstrated. Ferromagnetic metallic ground state in LMO films with the thickness down to 6 monolayers is stabilized by a combination of a La-deficiency and the interface-induced doping.Item DEVELOPMENT OF MATERIALS FOR THERMOELECTRIC GENERATORS: SUPERLATTICE Ca3Co4O9-Sr3Co4O9(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 ULTRATHIN MANGANITE LAYERS(2011) Șapoval, OlegEpitaxial La-deficient ultrathin films of La1-MnO3 (LMO) were grown by a metalorganic aerosol deposition technique with monolayer accuracy on SrTiO3 (STO) substrates and engineered by using different interfacial layers. The role of LaO-TiO2 interface in the formation of the ferromagnetic metallic state in very thin LMO films was demonstrated. The ferromagnetic metallic ground state in LMO films with the thickness down to 6 monolayers is stabilized by a combination of a La-deficiency and the interface-induced doping.Item CRYSTALLINE STRUCTURE, SURFACE MORPHOLOGY AND OPTICAL PROPERTIES OF NANOLAMELLAR COMPOSITES OBTAINED BY INTERCALATION OF InSe WITH Cd(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(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(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 THIN LAYER PHOTOVOLTAIC MODULES BASED ON CdS-CdTe HETEROJUNCTIONS(2011) Fiodorov, Vladimir; Gașin, Petru; Gagara, Ludmila; Chetruș, PetruA technology of thin layer photovoltaic modules with dimensions of 65 x 80 mm2 based on CdS-CdTe heterojunctions prepared via the quasi-closed volume technique was developed. The modules were made on a single glass plate; each element was positioned along the given plate so that the resulting module contains nine solar cells with an area of 3 cm2. The design of the module made it possible to study the energy parameters of each solar cell as well as the entire module. The study of the photovoltaic module based on CdS-CdTe heterojunctions showed the following parameters: short circuit current Isc = 270 mA; open circuit voltage Ucd = 0.786 V; FF =0.46, power discharged in the load Pmax ≈ 100 mW, and efficiency η ≈ 8.2% at the radiation power of 53 mW/cm2.Item NANOLAMELLAR STRUCTURES OF OXIDE-AIIIBVI:Cd SEMICONDUCTORS TYPE FOR USE AS DETECTORS OF RADIATION IN THE UV SPECTRAL REGION(Technical University of Moldova, 2011-07-07) Dmitroglo, Liliana; Untila, Dumitru; Chetruș, Petru; Evtodiev, Igor; Caraman, Iuliana; Lazăr, Gabriel; Nedeff, ValentinIn the paper, optical and photoelectrical properties of GaSe and InSe single crystal films of 10-5÷10-7 m submicron thickness and of semiconductor-native oxide structures obtained by annealing at (450÷700)°C in a normal atmosphere, are studied. The absorption spectrum of InSe lamella as well as of GaSe lamella in the energetic range from the red threshold up to 4,5 eV contains three bands with a rapid increase of the absorption coefficient which varies in the limits of (100÷106) cm-1 At the energies higher than 1,25 eV and 2,01 eV for InSe and GaSe respectively the light absorption are determined by the direct optical transitions in the centre of the Brillouin zone and at the energies higher than. At the absorption coefficients of (100÷102)cm-1 the indirect optic transitions are present. 3,0 eV also by the direct optical transitions in the points of the bands high symmetry. The resistive photosensitivity bands cover the spectral range Eg≤ hν ≤ 4,5 eV for lamellar photoresistors in which electric field EC6. The resistive photosensitivity band width could be controlled by the lamella thickness for d ≥1μm. The open circuit voltage spectral distribution is analysed from which results that at the oxidation temperature of 700°C in GaSe layer at the heterojunction interface the defects are formed on which the charge carriers, collected in the junction, are dissipated. The noneequilibrium charge carrier free path is of 0,8 μm.