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Item CARACTERIZAREA STRUCTURALĂ A STRATURILOR SUBȚIRI DE Sb2Te3 FABRICATE PRIN METODA SUBLIMĂRII ÎN VOLUM CUAZI-ÎNCHIS(CEP USM, 2024) Untila, Dumitru; Lungu, Ion; Suman, Victor; Gadiac, Ivan; Potlog, TamaraStraturi subțiri de Sb2Te3 au fost obținute pe suporturi de sticlă ITO/CdS prin metoda sublimării în volum cuazi-închis (CSS). Prin analiza difracției razelor X, s-a constatat că straturile subțiri de Sb2Te3 au rețea cristalină hexagonală, ce aparține grupului spațial P6/mmm. Creșterea temperaturii evaporatorului de la 470°C până la 530°C, duce la modificarea orientării preferabile de creștere a cristalitelor compusului Sb2Te3 și la creșterea gradului de cristalinitate a acestuia. Investigațiile Raman, au confirmat rezultatele XRD și au fost folosite pentru a obține informații suplimentare asupra structurii straturilor subțiri de Sb2Te3. Caracteristica dubletului observat la 119,54 cm–1 și 138,83 cm–1, precum și la 93,65 cm-1 si 107,36 cm-1 cu intensitate integrală foarte mică pot fi atribuite interacțiunii Te-Te între pachetele de telurură de antimoniu.Item SYNTHESIS AND ELECTROPHYSICAL PROPERTIES OF CdS/ZnTe HETEROJUNCTIONS(Academia de Ştiinţe a Moldovei, 2022) Lungu, Ion; Gagara, Lyudmila; Ghimpu, Lidia; Potlog, TamaraIn this paper results of studying CdS/ZnTe heterostructures synthesized by the quasi- closed space sublimation method on glass substrates coated with an ITO layer are described. The electrical and photoelectric properties of the structures are studied using current–voltage and capacitance–voltage characteristics in a temperature range of 30–100 °C. Analysis of the experimental data shows that the main specific feature of CdS/ZnTe structures is the formation of a high-resistance transition layer, which affects the separation of carriers at the barrier contact. The current carrier concentration in the space charge region, which is determined from the capacitance–voltage characteristics, is 1 1015 cm3; this fact suggests that one of the contacting materials—ZnTe—exhibits a high resistivity. Measurements of current–voltage characteristics in the solar cell mode give the following photoelectric parameters: open circuit voltage (UOC = 0.53 V, JSC = 27–30 A/cm2, and FF = 0.25.Item COPPER-RELATED DEFECTS IN ZnTe THIN FILMS GROWN BY THE CLOSE SPACE SUBLIMATION METHOD(Academia de Ştiinţe a Moldovei, 2022) Lungu, Ion; Ghimpu, Lidia; Untila, Dumitru; Potlog, TamaraLow-temperature photoluminescence (PL) is used to study defects evolution via immersion technique and annealing in vacuum of ZnTe thin films. In this paper we studied how copper doping from solutions of different molar concentrations affects PL of ZnTe thin films grown by close space sublimation (CSS) method. Undoped ZnTe thin films showed PL emission in the (520-680) nm wavelength region. The incorporation of copper in ZnTe produce a number of broad emission bands that correspond to an electron transition from the conduction band to spin-orbit states of the localized level of Cu2+ ions. All the studied samples had variable concentrations of oxygen and the possibility of the formation of auxiliary oxides is discussed.Item INFLUENȚA IODULUI ASUPRA PARAMETRILOR FOTOVOLTAICI AI CELULELOR SOLARE PE BAZA FTALOCIANINEI DE ZINC REALIZATE DIN SOLUȚII CHIMICE(CEP USM, 2020) Gadiac, Ivan; Lungu, Ion; Furtună, Vadim; Potlog TamaraItem FABRICAREA STRUCTURILOR SnO2/CdTe/ZnO ŞI CERCETAREA PROPRIETĂŢILOR ACESTORA(CEP USM, 2020) Lungu, Ion; Colibaba, Gleb; Potlog, TamaraItem FORMAREA STĂRII EXCITATE TRIPLET ÎN STRATURILE SUBȚIRI DOPATE CU Ga SINTETIZATE DIN SOLUȚIE(CEP USM, 2020) Rusnac, Dumitru; Lungu, Ion; Potlog, TamaraItem STRUCTURAL AND OPTICAL PROPERTIES OF ZNO:GA THIN FILMS DEPOSITED ON ITO/GLASS SUBSTRATES FOR OPTOELECTRONIC APPLICATIONS(Academia de Ştiinţe a Moldovei, 2021) Rusnac, Dumitru; Lungu, Ion; Colibaba, Gleb; Potlog, TamaraDoped (with GaCl3), undoped ZnO and ITO/ZnO:Ga nanostructured thin films are synthesized using the spray pyrolysis method. The doped ZnO thin films are synthesized at the atomic ratio of Ga/Zn added in the starting solution fixed at 1, 2, 3, and 5. Gallium-doped ZnO films synthesized on glass/ITO substrates are annealed at 4500C in different environments: vacuum, oxygen, and hydrogen. X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), and current–voltage (I–V) measurements are applied to characterize the structural properties, composition, surface morphology, and electrical properties of ZnO:Ga nanostructured thin films. X-ray diffraction analysis shows that ZnO:Ga films deposited on glass substrates have a dense and homogeneous surface with a hexagonal structure. The ZnO:Ga films deposited on glass/ITO substrates are composed of two phases, namely, hexagonal ZnO and cubic ITO. The I–V characteristics show the presence of good ohmic contacts between Al and In metals and ZnO:Ga thin films regardless of the nature of the substrate and the annealing atmosphere.Item ZnO NANOMETRIC LAYERS USED IN PHOTOVOLTAIC CELLS(Springer Nature, 2020) Botnariuc, Vasile; Gorceac, Leonid; Coval, Andrei; Cinic, Boris; Gaugas, Petru; Chetrus, Petru; Lungu, Ion; Raevschi, SimionThe 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.Item ELECTRICAL PROPERTIES OF THERMAL ANNEALED IN VACUUM SPRAY DEPOSITED AL-DOPED ZnO THIN FILMS(Springer Nature, 2020) Potlog, Tamara; Lungu, Ion; Raevschi, Simion; Botnariuc, Vasile; Robu, Stephan; Worasawat, Suchada; Mimura, HidenoriAl-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.Item EFECTUL DOPĂRII STRATURILOR DE ZnTe CU CUPRU ASUPRA PARAMETRILOR FOTOVOLTAICI AI HETEROSTRUCTURILOR ZnTe:Cu/CdTe(CEP USM, 2021) Lungu, IonÎn lucrare sunt investigate proprietățile fizice ale straturilor subțiri de ZnTe obținute prin metoda volumului cvasiînchis și apoi dopate cu cupru asupra caracteristicilor J-U ale heterostructurilor ZnTe:Cu/CdTe. Doparea straturilor de ZnTe cu cupru a fost efectuată în soluție chimică prin dizolvarea nitratului de Cu(II) în metanol. Pentru studiul proprietăților structurale a fost utilizată metoda difracției de raze X (XRD). Rezultatele analizei XRD relevă că straturile subțiri de ZnTe nedopate, precum și dopate cu Cu prezintă structură cristalină de tip zincblend cu orientarea preferențială (101). De asemenea, au fost studiate caracteristicile J-U ale heterostructurilor ZnTe:Cu/CdTe în dependență de concentrația molară a Cu(NO3)2 și de grosimea stratului de ZnTe:Cu.