Facultatea de Fizică şi Inginerie / Faculty of Physics and Engineering

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Author: search.filters.author.Lungu, IonEnd date: 2020

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    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, Hidenori
    Polycrystalline 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.
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    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, Leonid
    Structural, 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.
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    Fabricarea structurilor SnO2/CdTe/ZnO şi cercetarea proprietăţilor acestora [Articol]
    (CEP USM, 2020) Lungu, Ion; Colibaba, Gleb; Potlog, Tamara
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    ZnO nanometric layers used in photovoltaic cells [Articol]
    (Springer Nature, 2020) Botnariuc, Vasile; Gorceac, Leonid; Coval, Andrei; Cinic, Boris; Gaugas, Petru; Chetrus, Petru; Lungu, Ion; Raevschi, Simion
    The ZnO thin layers were grown on glass, InP and pInP-nCdS substrates from zinc acetate dissolved in water-acetic acid-methanol solution having a molarity of 0.2 M by using the spray method in the argon flow in the temperature range of (250–450) °C. The dependence of optical properties of ZnO layers on growth temperature have been investigated. The optical transmittance has values of 80–85% in the wavelength range of (200–1000) nm. The using of ZnO of the thickness of (60–80) nm as antireflective layers in nCdS-pInP structures allowed to increase the photovoltaic cell efficiency by 3%. The photosensitivity of the fabricated nZnO-pInP structures covers the wavelength region from 450 nm up to 1100 nm and allows the more efficient utilization of the incident light.
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    Electrical properties of thermal annealed in vacuum spray deposited al-doped zno thin films [Articol]
    (Springer Nature, 2020) Potlog, Tamara; Lungu, Ion; Raevschi, Simion; Botnariuc, Vasile; Robu, Stephan; Worasawat, Suchada; Mimura, Hidenori
    Al-doped ZnO thin films have been prepared by spray pyrolysis, which facilitates the incorporation of a higher percentage of dopant atoms. The vacuum thermally annealed at 420 °C temperature thin films have been characterized by X-ray diffraction (XRD), optical spectroscopy. Electrical conductivity and the Hall effect are investigated in the temperature interval (77–300) K. X-ray analysis results reveal that all the films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction (002) plane. Different characters of the temperature dependence of conductibility are observed in the Al-doped ZnO films vacuum thermally annealed at 420 °C temperature. In all cases, the conductivity, mobility carriers and carriers’ concentration of ZnO thin films obtained under Ar are higher than under O2 atmosphere, unless they are not doped. of your paper no longer than 300 words.
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    Influența dopării cu aluminiu asupra proprietăților optice ale straturilor subțiri de ZnO [Articol]
    (CEP USM, 2020) Lungu, Ion
    Straturile nanostructurate ZnO au fost sintetizate din soluții chimice prin metoda pirolizei pulverizate. Prin analiza difracției cu raze X (XRD) și a spectroscopiei UV-Vi sau fost studiate efectele variației concentrației de aluminiu asupra proprietăților optice ale straturilor nanostructurate de ZnO. Concentrația aluminiului în soluția inițială a fost fixată la 0, 1, 2, 3 și 5%.Analiza difracției cu raze X (XRD) confirmă că d oparea cu 1% de aluminiu, în comparație cu celelalte concentrații, îmbunătățește structura cristalină. Cu creșterea concentrației de aluminiu dimensiunea cristalitelor se micșorează. Studiul spectroscopiei UV-Vis a straturilor subțiri indică o transmitanță sporită (~90%) în regiunea vizibilă a spectrului energetic cu lărgimea benzii interzise de 3,23 eV pentru ZnO nedopat și de 3,32 eV pentru ZnO dopat cu Al, care este aproape de valoarea „bulk” a ZnO (3,36 eV).