Facultatea de Fizică şi Inginerie / Faculty of Physics and Engineering

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Author: search.filters.author.Untila, DumitruEnd date: 2018

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    Crystalline structure, surface morphology and optical properties of nanolamellar composites obtained by intercalation of InSe with Cd [Articol]
    (2015) Untila, Dumitru; Caraman, Iuliana; Evtodiev, Igor; Canțer, Valeriu; Spalatu, Nicolae; Leontie, Liviu; Dmitroglo, Liliana; Luchian, Efimia
    A material composed of InSe and CdSe crystallites was obtained by heat treatment at 753K of InSe single crystalline plates in Cd vapour for 3÷24 hours. The average diameters of CdSe and InSe crystallites determined from diffraction lines analysis are respectively equal to 20 nm and 22 nm. The photoluminescence spectra at 300K and 80K of composite decompose well into two Gaussian curves, one is in good correlation with the photoluminescence of CdSe crystals and the other is shifted to higher energies than the width of the band gap of CdSe crystals.
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    Nanolamellar structures of Oxide-AIIIBVI: Cd semiconductors type for use as detectors of radiation in the UV spectral region [Articol]
    (Technical University of Moldova, 2011-07-07) Dmitroglo, Liliana; Untila, Dumitru; Chetruș, Petru; Evtodiev, Igor; Caraman, Iuliana; Lazăr, Gabriel; Nedeff, Valentin
    In the paper, optical and photoelectrical properties of GaSe and InSe single crystal films of 10-5÷10-7 m submicron thickness and of semiconductor-native oxide structures obtained by annealing at (450÷700)°C in a normal atmosphere, are studied. The absorption spectrum of InSe lamella as well as of GaSe lamella in the energetic range from the red threshold up to 4,5 eV contains three bands with a rapid increase of the absorption coefficient which varies in the limits of (100÷106) cm-1 At the energies higher than 1,25 eV and 2,01 eV for InSe and GaSe respectively the light absorption are determined by the direct optical transitions in the centre of the Brillouin zone and at the energies higher than. At the absorption coefficients of (100÷102)cm-1 the indirect optic transitions are present. 3,0 eV also by the direct optical transitions in the points of the bands high symmetry. The resistive photosensitivity bands cover the spectral range Eg≤ hν ≤ 4,5 eV for lamellar photoresistors in which electric field EC6. The resistive photosensitivity band width could be controlled by the lamella thickness for d ≥1μm. The open circuit voltage spectral distribution is analysed from which results that at the oxidation temperature of 700°C in GaSe layer at the heterojunction interface the defects are formed on which the charge carriers, collected in the junction, are dissipated. The noneequilibrium charge carrier free path is of 0,8 μm.
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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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    Photoluminescence properties of lamellar nano-composites obtained by Cd intercalation of GaSe and GaSe: Eu single crystals [Articol]
    (2015) Untila, Dumitru; Cantser, Valeriu; Caraman, Mihail; Evtodiev, Igor; Leontie, Liviu; Dmitroglo, Liliana
    In this work surface morphology, composition and photo- luminescence at 293 K and 78 K, of composite obtained by intercalation of GaSe and GaSe:Eu (0.49 at.% and 1.00 at.%) single crystal lamellas with Cd from vapor phase at 753 K and 830 K are investigated. As-obtained composite consists of CdSe and microstructured GaSe single crystallites. Photoluminescence spectrum of GaSe:Eu single crystal lamellas is composed of Eu3+ emission band 5 7 5 7 0 1 0 2( ,D F D FÆ Æ , and 5 7 1 3D FÆ transitions) and indirect exciton line in GaSe crystallites. Emission spectrum of single crystalline GaSe−CdSe composite, at 78 K and 293 K, consists of donor-acceptor band in GaSe microcrystallites and emission band of CdSe crystallites. Composite derived from the intercala- tion of GaSe:Eu (0.49 at.%) single crystals with Cd ex- hibits strong visible luminescence. Its quasi-continuous photoluminescence spectrum is produced by superposi- tion of luminescent emissions of CdSe nano- and mi- croparticles, and microstructured GaSe.
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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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    Studiul structurii şi mecanisme de generare-recombinare în compozite nanolamelare obţinute prin intercalarea cu Cd a monocristalelor GaSe ŞI GaSe:Eu [Articol]
    (CEP USM, 2014) Untila, Dumitru; Dmitrolo, Liliana; Evtodiev, Igor; Caraman, Iuliana; Luchian, Efimia; Rotaru, Irina; Gorobcic, Tatiana
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    Instrumente interactive de măsură pentru învăţământul modern [Articol]
    (CEP USM, 2014) Luchian, Efimia; Evtodiev, Silvia; Rotaru, Irina; Untila, Dumitru
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    Soluţii de laborator experimental în domeniul ştiinţelor integrate [Articol]
    (CEP USM, 2014) Evtodiev, Igor; Evtodiev, Silvia; Oloieru, Vlad; Untila, Dumitru; Caraman, Mihail
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    Structura şi fotoluminescenţa compozitelor obţinute prin tratament termic în vapori de Cd a monocristalelor de Ga2S3 [Articol]
    (CEP USM, 2014) Vatavu, Elmira; Caraman, Iuliana; Evtodiev, Igor; Caraman, Mihail; Luchian, Efimia; Untila, Dumitru
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    Absorbtia luminii si fotoluminescenta cristalelor GaSe:Eu [Articol]
    (CEP USM, 2012) Untila, Dumitru
    GaSe monocrystals doped with 0,025%, 0,068%, 0,49% at. Eu, optically transparent in wavelengths domain λ>650 nm, were grown by Bridgman method. In addition to structural defects in ...Se-Ga-Ga-Se... stratified package, introduction of the Eu impurities in GaSe leads to the formation of Eu3+ luminescence centers. On the elementary package surface of GaSe doped with 0,49% at. Eu, there are neutral Eu atoms, what by thermic treatment at 400÷450ºC are forming a Eu2O3 and Ga2O3 composite layer.