Facultatea de Fizică şi Inginerie / Faculty of Physics and Engineering
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Item Composition, structure, and wear resistance of surface nanostructures obtained by electric spark alloying of 65G steel [Articol](2024) Yurchenco, E.; Ghilețchii, Gheorghe; Vatavu, Sergiu; Petrenco, Vladimir; Harea, Diana; Bubulincă, C.; Dikusar, AlexandrA combination of X-ray diffraction and X-ray fluorescence analysis has shown that the strength- ened layer formed during electric spark alloying of 65G steel with a processing electrode made of the T15K6 hard alloy is a nanocrystalline material, the ratio of the crystalline and amorphous phases in which is achieved by changing the discharge energy. Since an increase in discharge energy leads to an increase in surface rough- ness and its amorphization, there is an optimal value of discharge energy at which maximum wear resistance of the resulting nanocomposites is achieved. At E = 0.2 J, the wear resistance of the hardened layer is 7– 10 times higher than the wear resistance of the untreated surface.Item The structure polymer/as-se-s doped by bi for X-ray imaging [Articol](2023) Kiritsa, Arcady; Huștuc, Alexandru; Nasedchina, Nadejda; Vatavu, SergiuThe polymer/67at %(As 2S 3) 0,985 (Bi2Se3) 0,015:33 at.% As 2Se3 structure for X-ray imaging has been investigated. The possibility of registering relief-phase images for radiation of “white” spectrum of tungsten anode X-ray tube was shown.Item Сhalcogenide glassy semiconductors of the system as-se-s doped by te for X-ray imaging [Articol](2022) Kiritsa, Arcady; Spoială, Dorin; Vatavu, SergiuThe polymer/ As-Se-S-Te structure for X-ray imaging has been investigated. The possibility of registering relief-phase images for radiation of “white” spectrum and λ=0,154 nm of Cu anode X-ray tube was shown.Item Particularități structurale ale filmelor ZnSnN2 [Articol](CEP USM, 2024) Ghilețchii, Gheorghe; Narolschi, Igor; Rotaru, Corneliu; Rusu, Marin; Vatavu, SergiuZnSnN2 is composed of common non-toxic elements. It exhibits promising optoelectronic properties for application in photoelectric conversion and electromagnetic radiation detection devices. However, the available data on its physical properties are incomplete or contradictory. In this work, we prepare ZnSnN2 thin films and study in detail their structural properties as functi on of deposition conditions. DC magnetron sputtering was used because it allows the preparation of thin polycrystalline ZnSnN2 films on large areas and it can be easily upscaled. The films were prepared using targets of various atomic [Zn]/[Sn] ratios in nitrogen atmosphere at temperatures ranging from 30 to 300°C. Structural analysis, using Grazing Incidence X-ray Diffraction (GI XRD) and X-ray Reflectivity (XRR), revealed the formation of polycrystalline ZnSnN2 films with a wurtzite crystal structure. The obtained structural parameters were found to be influenced by the substrate temperature and elemental concentration in the target. These findings will be used for optimization of the manufacturing process for desired film characteristics.Item Structura și morfologia straturilor nanometrice de ZnSnN2 preparate prin magnetron sputtering [Articol](CEP USM, 2022-11-10) Narolschi, Igor; Ghilețchii, Gheorghe; Cliucanov, Alexandr; Rotaru, Corneliu; Spoială, Dorin; Vatavu, Elmira; Şapoval, Oleg; Belenciuc, Alexandr; Dmitroglo, Liliana; Bercu, Elena; Rusu, Marin; Vatavu, SergiuItem Straturi subțiri Ga2S3 pentru aplicații în detectori de radiații electromagnetice [Articol](CEP USM, 2022-11-10) Spoială, Dorin; Ghilețchii, Gheorghe; Vatavu, Elmira; Dmitroglo, Liliana; Şapoval, Oleg; Belenciuc, Alexandr; Rotaru, Corneliu; Narolschi, Igor; Vatavu, SergiuItem Metalorganic aerosol deposition: the building of oxide films [Articol](CEP USM, 2022-11-10) Şapoval, Oleg; Belenciuc, Alexandr; Vatavu, SergiuItem Metalorganic aerosol deposition technique [Articol](CEP USM, 2022-11-10) Şapoval, Oleg; Belenciuc, Alexandr; Vatavu, SergiuItem Dispozitive din fosfură de indiu bazate pe efectul fotovoltaic [Articol](CEP USM, 2021) Botnariuc, Vasile; Gorceac, Leonid; Coval, Andrei; Vatavu, Sergiu; Cinic, Boris; Rotaru, Corneliu; Raevschi, SimionHomo- și heterojoncțiunile din p - InP și n - CdS au fost confecționate aplicând metoda epitaxiei din faza gazoasă în volum deschis, în sistem de cloruri, metoda HVPE (Hydride Vapour Phase Epitaxy) și tehnologia în volum cvasiînchis, în hidrogen. S-a stabilit că eficiența celulelor fotovoltaice pe bază de heterojoncțiuni n+CdS-p-p+InP cu suprafața fotoactivă de 3 cm2 și pe homojoncțiuni n+- p- p+InP (1 cm2) constituie 12% și,respectiv, 7,3% în condiții de iluminare standard, AM1 (1000 Wm-2). Eficiența cuantică externă maximală constituie 75-80% pentru heterojoncțiunea n+CdS - p- p+ InP și 70% pentru homojoncțiunea n+-p-p+InP în intervalul (600-900) nm al spectrului electromagnetic. Fotosensibilitatea absolută maximă de 0,51 A/W este caracteristică pentru heterojoncțiunea n+CdS - p- p+InP cu strat epitaxial intermediar(p = 6,51016 cm-3). Astfel de heterojoncțiuni pot fi utilizate pentru elaborarea fotodetectorilor în intervalul VIS.Item Thermal transport evolution due to nanostructural transformations in Ga-doped indium-tin-oxide thin films [Articol](MDPI, 2021) Brinzari, Vladimir; Jeong, Do-Gyeom; Korotcenkov, Ghenadii; Vatavu, Sergiu; Lee, Jong S.; Nika, Denis; Cocemasov, AlexandrWe report on a comprehensive theoretical and experimental investigation of thermal conductivity in indium-tin-oxide (ITO) thin films with various Ga concentrations (0–30 at. %) deposited by spray pyrolysis technique. X-ray diffraction (XRD) and scanning electron microscopy have shown a structural transformation in the range 15–20 at. % Ga from the nanocrystalline to the amorphous phase. Room temperature femtosecond time domain thermoreflectance measurements showed nonlinear decrease of thermal conductivity in the range 2.0–0.5 Wm−1 K−1 depending on Ga doping level. It was found from a comparison between density functional theory calculations and XRD data that Ga atoms substitute In atoms in the ITO nanocrystals retaining Ia-3 space group symmetry. The calculated phonon dispersion relations revealed that Ga doping leads to the appearance of hybridized metal atom vibrations with avoided-crossing behavior. These hybridized vibrations possess shortened mean free paths and are the main reason behind the thermal conductivity drop in nanocrystalline phase. An evolution from propagative to diffusive phonon thermal transport in ITO:Ga with 15–20 at. % of Ga was established. The suppressed thermal conductivity of ITO:Ga thin films deposited by spray pyrolysis may be crucial for their thermoelectric applications.