Facultatea de Fizică şi Inginerie / Faculty of Physics and Engineering
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Item Nuclear quadrupole resonance of mixed-valence charge-ordered dimers [Articol](1999) Clochișner, Sofia; Gorceac, LeonidThe influence of an external magnetic field on the conditions of charge ordering of mixed-valence dimer clusters Ni 2q–Niq is considered. The manifestations of charge ordering in the spectra of nuclear quadrupole resonance are elucidated. These spectra are shown to give information on the key parameters of charge-ordered crystals.Item The caracterization of the CdS-based solar cell heterojunctions [Articol](Institute of Electrical and Electronics Engineers Inc., 2010-10-11) Potlog, Tamara; Botnariuc, Vasile; Gorceac, Leonid; Spalatu, Nicolae; Maticiuc, Natalia; Raevschi, SimionThe CdS-based solar cell heterojunctions (HJ) have been obtained by growth of CdS at relatively lower temperature using the close space sublimation method(CSS). Investigation of the photovoltaic characteristics shows an efficiency of about 12 % for InP/CdS and 9.6 % for CdS/CdTe solar cell HJ. The analysis of the forward dark current-voltage and the capacitance-voltage characteristics indicate a tunnelling recombination current which flows through states near or at the interfaces of a thermal energy of about 0.62 eV for CdS/CdTe and 0.42 eV for InP/CdS solar cell heterojunctions. The solar energy conversion efficiency is influenced by the interface states through the open circuit voltage and the fill factor.Item About the edge luminescence of cadmium sulphide thin layers grown on molybdenum [Articol](Institute of Electrical and Electronics Engineers, 1995-11-11) Raevschi, Simion; Gorceac, Leonid; Coval, Andrei; Chetruș, PetruCdS layers on to molybdenum were synthesized from separate elements in an open flowing hydrogen set. The surface micromorphology and some electrical and photoluminescent properties were investigated. The nature of layers edge photoluminescence peaks are discussed in the frames of the excitated exciton model.Item Thin AIN films growth on Si (III) by hydride vapor phase epitaxy [Articol](2008) Raevschi, Simion; Davydov, Valerii; Zhilaev, Yurii; Gorceac, Leonid; Botnariuc, VasileThin AlN layers have been grown on Si (111) by hydride vapor phase epitaxy (HVPE) method in a horizontal quartz reactor. The surface of layers has been studied by scanning electron microscopy and by the Raman spectroscopy method and found to have the structured morphology. It has been determined that the layers have high specific electrical resistance and are strained in the plane of the substrate.Item Straturi subţiri de CdS depuse din soluţii lichide (baie chimică) [Articol](CEP USM, 2011) Botnariuc, Vasilii; Gorceac, Leonid; Coval, Andrei; Raevschi, Simion; Micli, Valdec; Cinic, BorisThin layers of CdS were deposited on InP (100) substrates with a (3...5) arc degrees misorientation relative to (110) using water solutions of CdSO4, (NH4)2SO4, NH4OH, NH4Cl and CS(NH2)2 for synthesis. The morphology, atomic composition, photoluminescence and electrical properties of the deposited layers were investigated. The morphology of the CdS layers is characterized by a granular structure that is not changing under thermic treatment. A band in the energy interval (1,55 – 3,1) eV at 77 K with the maximum at 2,282 eV is observed in the photoluminescence spectra of the thin layers. Under thermic treatment from 200°C to 500°C in hydrogen the concentration of charge carriers is increasing from 2⋅1017 cm-3 to 2⋅1018 cm-3.Item Evoluarea particulelor dispersate de ALN depuse pe si prin metoda HVPE la etapa de formare a stratului continuu [Articol](CEP USM, 2011) Raevschi, Simion; Kompan, Mihail; Zhilyaev, Yurii; Gorceac, Leonid; Botnariuc, VasileEvolution of growth of the disperse particles of AlN which has been grown up on substrates of silicon during formation of a continuous layer are studies by AFM (Atomic Force Microscopy ) method. Layers have been grown up by HVPE (Hydride Vapor Phase Epitaxy) method at 1100o C. It is established: a) nunucleation occurs according to three dimensional model; b) layers are formed of two categories of disperse particles; c) growth rate of categories differ; d) at an initial stage of growth there is a latent period of time when superficial concentration of disperse particles remains to a constant.Item Structura suprafeţei straturilor de AlN depuse pe Si prin metoda HVPE la etapa iniţială de obţinere [Articol](CEP USM, 2010) Raevschi, Simion; Kompan, Mihail; Zhilyaev, Yurii; Gorceac, Leonid; Botnariuc, VasileThe surface structure of AIN layers deposited on the Silicon substrates at the initial stage of germination was studied by the Atomic Force Microscopy (AFM) method. The layers have been deposited by the Hydride Vapor Phase Epitaxy (HVPE) at 1100o C. It was determined that: a) germination follows the 3D model; b) mechanisms of layers growth are changing at the initial deposition stage; c) layers relief can be described in the approximation of a polynomial with elementary Gauss functions as arguments.Item Cercetarea celulelor solare cu heterojoncţiunea nCdS-pInP [Articol](CEP USM, 2009) Gorceac, Leonid; Botnariuc, Vasile; Raevschi, Simion; Coval, Andrei; Chitoroagă, AndreiPhotoelectrical dependencies of nCdS-pInP solar cells, as a function of electro physical parameters, crystallographic orientation of InP substrate and of the deposition duration of the nCdS epitaxial for layer are presented. It was established that the maximum value of the efficiency of solar energy into electrical one is obtained for the holes concentration in the substrate of 2·1016 cm-3, crystallographic orientation (100) and layer growth duration of 25 min. The hetero structure parameters influencing the named dependencies are determined.Item Obţinerea straturilor AIN pe Si prin metoda HVPE şi cercetarea proprietăţilor lor [Articol](CEP USM, 2008) Raevschi, Simion; Davydov, Valerii; Zhilyaev, Yurii; Gorceac, Leonid; Botnariuc, VasileAlN layers on Si(111) were fabricated by Hydride Vapor Phase Eptaxy (HVPE). The obtained layers were studied by using Raman spectroscopy and by scanning electron microscope (SEM). The layers surface is structured. The Raman spectra of the layers, obtained at the temperatures of 800-1100oC, are presented. It was established that the layers are mechanically deformed in substrate plane and have a high value of the threshold voltage (are dielectrics).Item Parametrii celulelor solare nITO/pInP obţinute prin metoda pulverizării pirolitice în dependenţă de tratarea lor termică în hidrogen [Articol](CEP USM, 2007) Simaşchevici, Alexei; Şerban, Dormidont; Gorceac, Leonid; Bruk, Leonid; Coval, Andrei; Usatîi, Iurie; Fedorov, VladimirThe main objective of this communication is the investigation of the influence of thermal treatment in H2on the parameters of In/nITO/P2O5/pInP/Ag:Zn solar cells obtained by ITO layers pyrolithic pulverization. The ITO/pInP heterostructures obtaining take place at the temperature of 450ºC. The photoelectric parameters of the solar cell received on InP wafers with concentration p = 3·1017cm-3after the thermal treatment are Voc=0.626 V, Isc = 22.72 mA/cm2, FF = 71%, Eff =10.09%. As a result of these investigations it was shown that the thermal treatment of In/nITO/pInP/Ag:ZnSC in H2at 350oC during 10 min. leads to considerable improvement of their photoelectric parameters.