Facultatea de Fizică şi Inginerie / Faculty of Physics and Engineering
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Item Micro and nanocomposites of gallium oxides and chalcogens as radiation receivers and gas sensors [Articol](Editura USM, 2024) Sprincean, Veaceslav; Caraman, MihailBy thermal treatment (TT) in water vapor atmosphere at 750 ℃ and 900 ℃ of β-GaS and εGaSe single-crystalline wafers, Ga2S3/Ga2Se3 - GaS/GaSe and β-Ga2O3 - GaSe/GaSe layers formed by nanowires and nanopangles photosensitive in the far Ultra-Violet (UVC) region were obtained. The electrical conductivity of β-Ga2O3 layer on GaS/GaSe substrate increases under the influence of water vapor. The link between the relative humidity of water vapor in the atmosphere and the electrical conductivity of the β-Ga2O3 layer was established.Item Utilizarea tehnologiilor avansate în fenotiparea plantelor și studiul unor procese metabolice la soiurile autohtone de soia (Glycine max (L.) Merrill.) [Articol](Editura USM, 2024) Bîrsan, Ana; Sprincean, Veaceslav; Savva, Marianna; Ganea, Ion; Guțu, Costel; Iacubuță, Maria; Paladi, FlorentinModern agriculture calls for the identification of efficient tools in plant phenotyping and the study of metabolic processes. CO2 sensors have been shown to be effective in the study of the gaseous metabolism of plants, subjected to abiotic stress, at various stages of growth and development, being easier to use compared to classical chemical methods and providing more accurate data. The use of CO2 sensors allowed the establishment of differences in the respiratory activity of rhizobacteria from the nodules of soybean varieties with different resistance to abiotic stress. Multispectral sensors provide data of real help in the phenotyping of agricultural crops, in establishing the physiological state of plants at different stages of development, but also in identifying field problems, demonstrating opportunities for their use in monitoring agricultural fields and improving the quality of agro-ecosystem services. Phenotyping with the help of hyper/multispectral imaging allows obtaining valuable, high precision scientific results with reference to plant health.Item Parcul digital 3D al monumentelor de arhitectură din Chișinău: inovație și valorificarea patrimoniului cultural [Articol](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 [Articol](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 [Articol](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 Preparation, chemical composition, and optical properties of (β–Ga2O3 composite thin films)/(GaSxSe1−x lamellar solid solutions) nanostructures [Articol](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.