2. Articole
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Item Parcul digital 3D al monumentelor de arhitectură din Chișinău: inovație și valorificarea patrimoniului cultural(Editura USM, 2024) Sprincean, Veaceslav; Pascari, Serghe; Savva, Marianna; Matveev, SergiuUAV-based photogrammetry technologies allow the architectural and aesthetic details of monuments to be captured with extreme precision, which helps to thoroughly document their current condition. These models can be used for further restoration, even if the monument would suffer degradation or destruction. The 3D models act as a digital archive of monuments, making it possible to preserve cultural elements in virtual format even if they physically disappear.Item COMPOSITION AND SURFACE OPTICAL PROPERTIES OF GASE:EU CRYSTALS BEFORE AND AFTER HEAT TREATMENT(2024) Sprincean, Veaceslav; Haoyi, Qiu; Tjardts, Tim; Lupan, Oleg; Untila, Dumitru; Aktas, Oral Cenk; Adelung, Rainer; Leontie, Liviu; Cârlescu, Aurelian; Gurlui, Silviu; Caraman, MihailThis work studies the technological preparation conditions, morphology, structural char- acteristics and elemental composition, and optical and photoluminescent properties of GaSe single crystals and Eu-doped β–Ga2O3 nanoformations on ε–GaSe:Eu single crystal substrate, obtained by heat treatment at 750–900 ◦C, with a duration from 30 min to 12 h, in water vapor-enriched atmosphere, of GaSe plates doped with 0.02–3.00 at. % Eu. The defects on the (0001) surface of GaSe:Eu plates serve as nucleation centers of β–Ga2O3:Eu crystallites. For 0.02 at. % Eu doping, the fundamental absorption edge of GaSe:Eu crystals at room temperature is formed by n = 1 direct excitons, while at 3.00 at. % doping, Eu completely shields the electron–hole bonds. The band gap of nanostructured β–Ga2O3:Eu layer, determined from diffuse reflectance spectra, depends on the dopant concentration and ranges from 4.64 eV to 4.87 eV, for 3.00 and 0.05 at. % doping, respectively. At 0.02 at. % doping level, the PL spectrum of ε–GaSe:Eu single crystals consists of the n = 1 exciton band, together with the impurity band with a maximum intensity at 800 nm. Fabry–Perrot cavities with a width of 9.3 μm are formed in these single crystals, which determine the interference structure of the impurity PL band. At 1.00–3.00 at. % Eu concentrations, the PL spectra of GaSe:Eu single crystals and β–Ga2O3:Eu nanowire/nanolamellae layers are determined by electronic transitions of Eu2+ and Eu3+ ions.Item SYNTHESIS AND PROPERTIES OF β-Ga2O3 NANOWIRES AND NANOSHEETS ON DOPED GaS:Mn SUBSTRATES(2024) Sprincean, Veaceslav; Haoyi, Qiu; Lupan, Oleg; Tjardts, Tim; Petersen, Deik; Veziroglu, Salih; Adelung, Rainer; Caraman, MihailIn this work, the synthesis, morphology, optical and luminescence properties of Mn-doped β-Ga2O3 (Ga2O3:Mn) nanowires/nanosheets on Mn-doped GaS (GaS:Mn) substrate are studied. The aim was to obtain structures of semiconductors with layers of nanoformations (nanowires, nanosheets) from a wide energy band semiconductor such as β-Ga2O3 and to determine their characteristic properties. For the base material, Mn-doped GaS lamellae were chosen, which are optically transparent in the spectral region where the optical properties of Mn2+ and Mn3+ ions are manifested. Through thermal annealing, single-crystalline β-GaS plates doped with 1.3 atomic percent (at.%) of manganese (Mn) are exposed to an atmosphere enriched with H2O vapor at a temperature of 800 ◦C for 6 h. As a result, the surface of these plates is covered with a composite layer consisting of crystallites of α-Ga2S3:Mn and β-GaS:Mn planar junctions. This composite exhibits a direct band gap of 2.88 eV and an indirect band gap of 2.55 eV corresponding to the β-GaS:Mn crystallites. Upon further increasing the temperature during thermal annealing to 850 ◦ C and 920 ◦C, the surface of the β-GaS:Mn samples transform into a layer of β-Ga2O3: Mn nanowires/nanosheets with a band gap of 4.5 eV. Its intense green-orange photoluminescence is caused by electronic transitions within the Mn2+ ion.Item CRYSTALLINITY AND OPTICAL PROPERTIES OF β-Ga2O3/Ga2S3 LAYERED STRUCTURE OBTAINED BY THERMAL ANNEALING OF Ga2S3 SEMICONDUCTOR(2021) Sprincean, Veaceslav; Lupan, Oleg; Caraman, Iuliana; Untila, Dumitru; Postica, Vasile; Cojocaru, Ala; Gapeeva, Anna; Palachi, Leonid; Adeling, Rainer; Tiginyanu, Ion; Caraman, MihailIn this work, the β-Ga2O3 nanostructures were obtained by thermal annealing in air of β-Ga2S3 single crystals at relatively high temperatures of 970 K, 1070 K and 1170 K for 6 h. The structural, morphological, chemical and optical properties of β-Ga2O3–β-Ga2S3 layered composites grown at different temperatures were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) as well as photoluminescence spectroscopy (PL) and Raman spectroscopy. The results show that the properties of obtained β-Ga2O3–β-Ga2S3 composites were strongly influenced by the thermal annealing tem- perature. The XRD and Raman analyses confirmed the high crystalline quality of the formed β-Ga2O3 nano- structures. The absorption edge of the oxide is due to direct optical transitions. The optical bandwidth was estimated to be approximately 4.34-4.41 eV, depending on the annealing temperature. Annealing of the β-Ga2S3 monocrystals at a higher temperature of 1170 K showed the complete conversion of the surface to β-Ga2O3. These results demonstrate the possibility to grow high quality β-Ga2O3–β-Ga2S3 layered composites and β-Ga2O3 nanostructures in large quantities for various applications such as gas sensing, non-toxic biomedical imaging, nonlinear optical, as well as power device applications. Micro and nanocrystallites present on the surface of the Ga2O3 layer contribute to a diffusion of the incident light which leads to an increase of the absorption rate allowing thus to reduce the thickness of the Ga2O3 layer, in which the generation of unbalanced charge carriers takes place. By decreasing the Ga2O3 layer thickness in such layered composites, the efficiency of photovoltaic cells based on such junctions can be increased.Item OPTICAL AND PHOTOSENSITIVE PROPERTIES OF FLEXIBLE n (p)–InSe/In2O3 HETEROJUNCTIONS(2022) Sprincean, Veaceslav; Leontie, Liviu; Caraman, Iuliana; Untila, Dumitru; Girtan, Mihaela; Gurlui, Silviu; Lisnic, Petru; Doroftei, Corneliu; Cârlescu, Aurelian; Iaconi, Felicia; Caraman, MihailIn this work, optical, including photoluminescence and photosensitivity, characteristics of micrometer-sized flexible n (p)–InSe/In2O3 heterojunctions, obtained by heat treatment of single- crystalline InSe plates doped with (0.5 at.%) Cd (Sn), in a water-vapor- and oxygen-enriched at- mosphere, are investigated. The Raman spectrum of In2O3 layers on an InSe:Sn substrate, in the wavelength range of 105–700 cm−1, contains the vibration band characteristic of the cubic (bcc-In2O3) phase. As revealed by EDX spectra, the In2O3 layer, ~2 μm thick, formed on InSe:Cd contains an ~18% excess of atomic oxygen. The absorption edge of InSe:Sn (Cd)/In2O3 structures was stud- ied by ultraviolet reflectance spectroscopy and found to be 3.57 eV and ~3.67 eV for InSe:Cd and InSe:Sn substrates, respectively. By photoluminescence analysis, the influence of doping impuri- ties on the emission bands of In2O3:Sn (Cd) was revealed and the energies of dopant-induced and oxygen-induced levels created by diffusion into the InSe layer from the InSe/In2O3 interface were determined. The n (p)–InSe/In2O3 structures display a significantly wide spectral range of photosen- sitivity (1.2–4.0 eV), from ultraviolet to near infrared. The influence of Cd and Sn concentrations on the photosensitivity and recombination of nonequilibrium charge carriers in n (p)–InSe layers from the heterojunction interface was also studied. The as-obtained nanosized InSe/In2O3 structures are suitable for optoelectronic applications.Item PREPARATION, CHEMICAL COMPOSITION, AND OPTICAL PROPERTIES OF (β–Ga2O3 COMPOSITE THIN FILMS)/(GaSxSe1−x LAMELLAR SOLID SOLUTIONS) NANOSTRUCTURES(2023) Sprincean, Veaceslav; Leontie, Liviu; Caraman, Iuliana; Lupan, Oleg; Adeling, Rainer; Gurlui, Silviu; Cârlescu, Aurelian; Doroftei, Corneliu; Caraman, MihailGaSxSe1−x solid solutions are layered semiconductors with a band gap between 2.0 and 2.6 eV. Their single crystals are formed by planar packings of S/Se-Ga-Ga-S/Se type, with weak polarization bonds between them, which allows obtaining, by splitting, plan-parallel lamellae with atomically smooth surfaces. By heat treatment in a normal or water vapor-enriched atmosphere, their plates are covered with a layer consisting of β–Ga2O3 nanowires/nanoribbons. In this work, the elemental and chemical composition, surface morphology, as well as optical, photoluminescent, and photoelectric properties of β–Ga2O3 layer formed on GaSxSe1−x (0 ≤ x ≤ 1) solid solutions (as substrate) are studied. The correlation is made between the composition (x) of the primary material, technological preparation conditions of the oxide-semiconducting layer, and the optical, photoelectric, and photoluminescent properties of β–Ga2O3 (nanosized layers)/GaSxSe1−x structures. From the analysis of the fundamental absorption edge, photoluminescence, and photoconductivity, the character of the optical transitions and the optical band gap in the range of 4.5–4.8 eV were determined, as well as the mechanisms behind blue-green photoluminescence and photoconduc- tivity in the fundamental absorption band region. The photoluminescence bands in the blue-green region are characteristic of β–Ga2O3 nanowires/nanolamellae structures. The photoconductivity of β–Ga2O3 structures on GaSxSe1−x solid solution substrate is determined by their strong fundamental absorption. As synthesized structures hold promise for potential applications in UV receivers, UV-C sources, gas sensors, as well as photocatalytic decomposition of water and organic pollutants.Item UTILIZAREA UAV ÎN CERCETĂRILE ARHEOLOGICE DIN BAZINUL RÂULUI COGÂLNIC. SITUL LIPOVENI II-LA NISIPĂRIE(CEP USM, 2022-11-10) Matveev, Sergiu; Sprincean, Veaceslav; Vornic, VladItem DETECTAREA SEMNALELOR DE FLUORESCENȚĂ A PLANTELOR LA DISTANŢĂ CU FOLOSIREA UAV(CEP USM, 2022-11-10) Chiriţa, Arcadii; Sprincean, Veaceslav; Savva, Marianna; Paladi, FlorentinItem FOTOREZISTOR PENTRU REGIUNEA ULTRAVIOLETĂ PE BAZĂ DE STRAT DIN NANOFIRE DE β-Ga2O(CEP USM, 2022-11-10) Vatavu, Elmira; Sprincean, Veaceslav; Dmitroglo, Liliana; Gurău, Virginia; Caraman, MihailItem PROCESE DE GENERARE-RECOMBINARE A PURTĂTORILOR DE SARCINĂ DE NEECHILIBRU ÎN COMPOZITUL Ga2O3/Ga2Se3 ȘI ÎN STRUCTURILE MICROLAMELARE - Ga2O3/GaSe(CEP USM, 2020) Sprincean, Veaceslav; Dmitroglo, Liliana; Vatavu-Cuculescu, Elmira; Caraman, Mihail