Facultatea de Fizică şi Inginerie / Faculty of Physics and Engineering
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Item Secondary ion mass spectroscopy of zinc selenide crystals with photoconductivity spectral memory [Articol](2017) Belenciuc, Alexandr; Ilinykh, Nicolai; Kovalev, LeonidItem 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-AlThe 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.Item Synthesis and properties of Al-doped ZnO thin films for photovoltaics [Articol](Institute of Electrical and Electronics Engineers Inc., 2018-11-27) Potlog, Tamara; Lungu, Ion; Botnariuc, Vasile; Gorceac, Leonid; Raevschi, Simion; Taku, Miyake; Worasawat, Suchada; Mimura, HidenoriPolycrystalline undoped and Al-doped ZnO thin films were deposited by spray pyrolysis using oxygen and argon atmospheres. The influence of postdeposition vacuum annealing on the structure, morphology and optical properties was studied by X-ray diffraction, atomic force microscopy and UV–VIS spectroscopy. The thermal vacuum annealing induces structural and morphological changes, especially in Al-doped ZnO thin films synthetized in oxygen atmosphere. Further on, the electrical conductivity in dependence of the nature of gas atmosphere and Al concentration is discussed.Item Effect of carrier gas and vacuum annealing on the physical properties of ZnO thin films doped with gallium by chemical spray pyrolysis [Articol](Editura "Tehnica-UTM", 2018-05-24) Potlog, Tamara; Lungu, Ion; Botnariuc, Vasile; Raevschi, Simion; Worasawat, Suchada; Mimura, Hidenori; Gorceac, LeonidStructural, optical and electrical properties of zinc oxide thin films doped with 2% Ga, annealed in the vacuum at the same temperature and obtained onto glass substrates by the chemical spray pyrolysis method in the different gas atmospheres were investigated by X-ray Diffraction (XRD), UV-VIS spectrophotometry and Hall measurements, respectively. XRD studies revealed that all films were polycrystalline in nature, with a hexagonal wurtzite crystal structure and a predominant (002) c-axis orientation. All ZnO:Ga thin films had higher than 80 % transmittances in the visible region. Doping with 2% Ga led to a decrease in the optical band gap indifferent of the nature of the carrier gas. The synthesis of ZnO thin films with 2% Ga doping and annealing in the same conditions in Ar and O2 atmospheres led to the lower conductivity with electron concentration of 1016 cm−3.Item 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.Item 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, MihailThe 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.Item Photoelectric and photoluminescence properties of CdTe–GaTe composite [Articol](2016) Caraman, Iuliana; Spalatu, Nicolae; Evtodiev, Igor; Untila, Dumitru; Leontie, Liviu; Caraman, MihailA 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.Item Comportarea nichelului în antimonidul de galiu ca dopant [Articol](2016) Gheorghiță, Andrian; Gheorghiță, Eugeniu; Guțuleac, Leonid; Caraman, Mihail; Korolevski, Boris; Untilă, Pantelei; Melinte, VictoriaÎn 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.Item Structura spectrelor de reflexie ale antimonidului de galiu dopat cu fier [Articol](2016) Aramă, Efim; Gheorghiță, Eugen; Mihălache, Alexei; Palachi, Leonid; Caraman, Mihail; Melinte, VictoriaItem Caracterizarea structurală a nanoformațiunilor de Ga2O3 obținute prin tratament termic al monocristalelor Ga2O3 [Articol](Universitatea Tehnică din Moldova, 2018-05-24) Untilă, Dumitru; Sprincean, Veaceslav; Caraman, Mihail; Cojocaru, Ala; Lupan, Oleg; Tighineanu, Ion; Palachi, Leonid; Caraman, IulianaPrin tratament termic (TT), în atmosferă normală, al monocristalelor β-Ga2S3, cu rețea cristalină monoclinică, la temperaturi din intervalul 970-1170 K, timp de 3-6 ore, suprafața acestora se acoperă cu un strat omogen de β-Ga2O3, cu rețea cristalină monoclinică. La interfața monocristal-oxid se formează nanocristalite de Ga2O3 și Ga2S3. Structura cristalină și dimensiunile medii ale cristalitelor sunt analizate prin măsurări XRD, SEM și Raman.