Facultatea de Fizică şi Inginerie / Faculty of Physics and Engineering

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Start date: 2016End date: 2016

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    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-Al
    The 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.
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    Silicon solar cells based on pSi/nSi3N4 nanolayers [Articol]
    (2016) Zakhvalinskii, Vasilii; Pilyk, E.; Goncharov, I.; Simașchevici, Alexey; Șerban, Dormidont; Bruc, Leonid; Curmei, Nicolai; Rusu, Marin; Rodrigez, G.
    Thin films of Si 3N4 were prepared by non-reactive magnetron sputtering in an Ar atmosphere. A previously synthesized Si 3N4 was used as a solid-state target. Deposition was carried out on a cold substrate of p-Si (1 0 0) with a resistivity of 2 Ohm cm. The Raman spectrum of the deposited Si 3N 4 layers has been investigated. The position of the maximum in the Raman scattering spectrum of Si3 N4 layers corre sponds to the Si3 N4 compound and the shape of the spectrum is characteristic for the nanocrystalline state of the cubic modification of silicon nitride. The film thickness has been determined from atomic force microscopy measurements. The results of electron diffraction investigations of n-Si3 N4 nanolayers with thicknesses up to 20 nm demonstrates that as-deposited Si 3N4 thin films consist of a mixture of microcrystalline and amorphous phases. Solar cells based on heterostructures consisting of a p-type Si (1 0 0) and n-type Si 3N4 nanolayers were fabricated and studied.
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    Photoluminescence of Nanocomposites Obtained by Heat Treatment of GaS, GaSe, GaTe and InSe Single Crystals in Cd and Zn Vapor [Articol]
    (2016) Evtodiev, Igor; Caraman, Iuliana; Kantser, Valeriu; Untila, Dumitru; Rotaru, Irina; Dmitroglo, Liliana; Evtodiev, Silvia; Caraman, Mihail
    The photoluminescence (PL) spectra of GaS, GaSe, GaTe and InSe semiconductors used as the basis materials to obtain nanocomposite by heat treatment in Zn and Cd vapor were studied. The PL spectra of ZnS–GaS, CdSe– GaSe, CdSe–InSe, ZnSe–InSe composites consist of wide bands covering a wide range of wavelengths in the antistokes region for CdSe, ZnSe and GaS crystallites from composites. The antistokes branches of spectra are interpreted as the shift of PL bands to high energies for nanosized crystallites.
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    Photoelectric and photoluminescence properties of CdTe–GaTe composite [Articol]
    (2016) Caraman, Iuliana; Spalatu, Nicolae; Evtodiev, Igor; Untila, Dumitru; Leontie, Liviu; Caraman, Mihail
    A GaTe–CdTe composite was obtained by thermal treatment at 1020 K of GaTe single crystals in Cd vapor atmosphere. The composite photoluminescence, photoconductivity, and com- position are studied in this work. The photosensitivity and photoluminescence band structure are determined for both the primary crystals and the composite. The CdTe crystallites create, in the GaTe bandgap, recombination and trapping levels, which determine the structure of the photoluminescence spectra and the spectral range of composite photosensitivity. The photoluminescence spectrum of the composite at 80 K contains characteristic bands of both composite components, GaTe and CdTe. From the analysis of thermally stimulated luminescence curves, the energies of the electron trapping levels in the composite are determined.
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    Comportarea nichelului în antimonidul de galiu ca dopant [Articol]
    (2016) Gheorghiță, Andrian; Gheorghiță, Eugeniu; Guțuleac, Leonid; Caraman, Mihail; Korolevski, Boris; Untilă, Pantelei; Melinte, Victoria
    În lucrare se analizează particularitățile proprietăților fizice ale antimonidului de galiu dopat cu nichel pentru un diapazon vast de concentrații, până la 3% atomare și temperaturi (2÷300)K. Din analiza în ansamblu a efectelor galvanomagnetice, optice și de iradiere se evidențiază în premieră un șir de particularități ale proprietăților fizice determinate de interacțiunea purtătorilor de sarcină cu momentul magnetic excitat de structura energetică a substratului electronic incomplet 3d.
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    Structura spectrelor de reflexie ale antimonidului de galiu dopat cu fier [Articol]
    (2016) Aramă, Efim; Gheorghiță, Eugen; Mihălache, Alexei; Palachi, Leonid; Caraman, Mihail; Melinte, Victoria
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    Фотовольтаические структуры ITO/SiOх/n-Si повышенной эффективности [Articol]
    (2016) Симашкевич, Алексей; Шербан, Дормидонт; Караман, Михаил; Русу, Марин; Брук, Леонид; Курмей, Николай
    Изготовлены структуры ITO/SiOх/n-Si пульверизацией растворов хлоридов индия и олова на поверхность (100) пластин кремния с удельным сопротивлением 4,5 Ом·см. Изучено влияние состояния поверхности Si на эффективность структур как фотоэлектрических преобразовате- лей. Показано, что наиболее эффективными являются структуры с непротравленной поверхно- стью пластин кремния. Солнечные элементы на основе исследованных структур ITO/SiOх/n-Si c инверсным слоем демонстрируют в условиях АМ 1,5 эффективность, близкую к 16%.
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    Approximate analysis of the diffraction efficiency of transmission phase holographic gratings with smooth non-sinusoidal relief [Articol]
    (2016) Andries, Ion; Galstian, Tigran; Chirita, Arcadi
    In the article is presented the electro-dynamic model and method for numerical analysis of the diffraction efficiency of thin holographic diffraction gratings. Self-developing holographic gratings are easy to fabricate and can provide relatively high diffraction efficiency. Some photosensitive materials, such as chalcogenide glassy semiconductors of doped As-S-Se-Sn system used in a photo-thermoplastic recording process demonstrate the ability of registration the relief-phase gratings with efficiency up to 40% in transmitted light. The efficiency is highly dependent on the grating profile shape (groove shape and depth). Theoretical analysis is performed using the method of spectral expansions for periodic lattices. Semi-analytical dependences of efficiency on parameters of lattices with arbitrary continuous profile, including experimentally measured one by AFM, are obtained. They allow without using cumbersome numerical calculations to obtain the optimal shape of the lattice profile with maximum efficiency in a given diffraction order. A satisfactory agreement between numerical calculations and experimental measurements is demonstrated. It is shown that the optimal shape of the lattice for maximum efficiency tends to that of a symmetrical binary grating for which the theoretical limiting value of efficiency is 40.5%.
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    Testing of electrical methods of exposure on warm cloud to induce precipitations [Articol]
    (2016) Zasavitsky, E.; Kantser, V.; Sidorenko, A.; Belenchuk, A.; Shapoval, O.; Chirita, A.
    We implemented optical technique for testing of full-size pyrotechnical rocket generators of aerosols utilized currently both for the protecting of agricultural crops from hail damage as well as in the experimental modification of precipitation [1]. The elaborated method allows tracking the dynamics of the process in climate chamber and fast calculation of cloud parameters and ice/water droplet-forming process. Powerful cumulonimbus cloud is a metastable system, in which to cause precipitation enough only a small external influence. Along with the thermodynamic phase instability in clouds take place the instability of electric origin. The processes of condensation and coagulation evolve on the background electric fields in the atmosphere and the formation of electric charges of the droplets and crystals [2, 3]. We report on experimental study of electrical methods of exposure on warm cloud to induce precipitations. We investigated the direct impact of high electric field in clouds that affect the phase and microstructure transformations of atmospheric moisture, to regulate the development of rainfall process. Corona induces the water drops falling down at temperatures of testing clouds +2ºC. The estimated efficiency of corona impact at field strength 104 V/cm was close to expose of hygroscopic reagent on testing cloud. The mean size of registered droplets was slightly bigger than mean size cloud droplets 20-30 μm whereas density of deposited droplets decreased dramatically with decreasing of field strength. The second approach presented in this work is investigation of impact of electrically charged aerosols on testing cloud. We demonstrate high efficiency of the initiation of rainfall induced by sprayed charged particles of Portland cement. The methods of introducing and parameters of charged aerosols are under discussion.
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    Conductometric gas sensors based on metal oxides modified with gold nanoparticles : a review [Articol]
    (Springer, 2016) Korotcenkov, Ghenadii; Brinzari, Vladimir; Cho, Beong K.
    This review (with 170 refs.) discusses approaches towards surface functionalizaton of metal oxides by gold nanoparticles, and the application of the resulting nanomaterials in resistive gas sensors. The articles is subdivided into sections on (a) methods for modification of metal oxides with gold nanoparticles; (b) the response of gold nanoparticle-modified metal oxide sensors to gaseous species, (c) a discussion of the limitations of such sensors, and (d) a discussion on future tasks and trends along with an outlook. It is shown that, in order to achieve significant improvements in sensor parameters, it is necessary to warrant a good control the size and density of gold nanoparticles on the surface of metal oxide crystallites, the state of gold in the cluster, and the properties of the metal oxide support. Current challenges include an improved reproducibility of sensor preparation, better long-term stabilities, and a better resistance to sintering and poisoning of gold clusters during operation. Additional research focused on better understanding the role of gold clusters and nanoparticles in gas-sensing effects is also required.