Browsing by Author "Rusu, Marin"

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ELLIPSOMETRIC STUDIES OF NANOMETRIC CdS AND CdTe FILMS
(2005) Caraman, Mihail; Evtodiev, Igor; Cuculescu, Elmira; Rusu, Marin; Salaoru, Iurie
The thickness of the layers CdS and CdTe grown on the Si, Ge, GaAs was determined from the analysis of the polarization ellipse of the reflected light from the surfaces of structures thin layers substrate. The thermal treatment of the samples CdS-CdTe in the presence of CdCl2 leads to the increasing of the crystalline phase from layers.
THE INVESTIGATION OF TCO/CdS/CdTe HETEROJUNCTIONS BY C-U and C-f MEASUREMENTS: EXPERIMENT AND MODELING
(IEEE, 2013) Rotaru, Corneliu; Vatavu, Sergiu; Fedorov, Vladimir; Gașin, Petru; Lux-Steiner, Martha; Ferekides, Chris; Rusu, Marin
The paper presents the analysis of C-U and C-f data obtained in the 1 kHz-10 MHz range for CdS/CdTe heterojunctions prepared by CSS onto (ZnO:Al, ZnO:Al/i-ZnO)/Glass substrates. An attempt to model the physical properties of the heterojunctions is made. A small signal analysis has been carried out to establish the equivalent circuit of device. The unusual capacitance behavior of the ZnO based heterojunction is attributed to presence of the barrier at the back contact.
PARTICULARITĂȚI STRUCTURALE ALE FILMELOR ZnSnN2
(CEP USM, 2024) Ghilețchii, Gheorghe; Narolschi, Igor; Rotaru, Corneliu; Rusu, Marin; Vatavu, Sergiu
ZnSnN2 is composed of common non-toxic elements. It exhibits promising optoelectronic properties for application in photoelectric conversion and electromagnetic radiation detection devices. However, the available data on its physical properties are incomplete or contradictory. In this work, we prepare ZnSnN2 thin films and study in detail their structural properties as functi on of deposition conditions. DC magnetron sputtering was used because it allows the preparation of thin polycrystalline ZnSnN2 films on large areas and it can be easily upscaled. The films were prepared using targets of various atomic [Zn]/[Sn] ratios in nitrogen atmosphere at temperatures ranging from 30 to 300°C. Structural analysis, using Grazing Incidence X-ray Diffraction (GI XRD) and X-ray Reflectivity (XRR), revealed the formation of polycrystalline ZnSnN2 films with a wurtzite crystal structure. The obtained structural parameters were found to be influenced by the substrate temperature and elemental concentration in the target. These findings will be used for optimization of the manufacturing process for desired film characteristics.
SILICON CARBIDE NANOLAYERS AS A SOLAR CELL CONSTITUENT
(2015) Zakhvalinskii, Vasilii; Pilyk, Evghenii; Goncharov, Igor; Simașchevici, Alexei; Șerban, Dormidont; Bruc, Leonid; Curmei, Nicolai; Rusu, Marin
Thin films of predominantly amorphous n-type SiC were prepared by non-reactive magnetron sputtering in an Ar atmosphere. A previously synthesized SiC was used as a solid-state target. Deposition was carried out on a cold substrate of p-type Si (100) with a resistivity of 2 Vcm. The Raman spectrum shows a dominant band at 982 cm 1 , i.e., in the spectral region characteristic for SiC. It was found that the root mean square roughness varies from about 0.3 nm to 9.0 nm when the film thickness changes from about 2 nm to 56 nm, respectively. Transmission electron microscopy studies showed that SiC thin films consist predominantly of an amorphous phase with inclusions of very fine nanocrystallites. A heterostructure consisting of a p-type Si (100) and a layer of predominantly amorphous n-type SiC was fabricated and studied. The investigation of its electrical and photoelectric properties shows that the entire space charge region is located in Si. This is in addition confirmed by the spectral dependence of the p-Si/n-SiC photosensitivity. The barrier height at the p-Si/n-SiC interface estimated from dark I–V characteristics is of the order of 0.9–1.0 eV. Load I–V characteristics of p-Si/n-SiC-nanolayer solar cells demonstrate under standard AM1.5 illumination conditions a conversion efficiency of 7.22%.
SILICON SOLAR CELLS BASED ON pSi/nSi3 N 4 NANOLAYERS
(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.
STRATURI SUBȚIRI SEMICONDUCTOARE PREPARATE ÎN SISTEME DE PULVERIZARE CU MAGNETRON (DC): TEORIE vs EXPERIMENT (I)
(CEP USM, 2020) Narolschi, Igor; Cliucanov, Alexandr; Rotaru, Corneliu; Rusu, Marin; Vatavu, Sergiu
Caracteristica curent-tensiune a sistemului de pulverizare cu magnetron(DC) depinde în formă pătratică de trei parametri,unul dintre care este egal cu potențialul de aprindere a descărcării gazului, pe când ceilalți doi parametri se determină experimental din caracteristica curent-tensiune pentru valori mici sau mari ale tensiunii aplicate sistemului.
STRUCTURA ȘI MORFOLOGIA STRATURILOR NANOMETRICE DE ZnSnN2 PREPARATE PRIN MAGNETRON SPUTTERING
(CEP USM, 2022-11-10) Narolschi, Igor; Ghilețchii, Gheorghe; Cliucanov, Alexandr; Rotaru, Corneliu; Spoială, Dorin; Vatavu, Elmira; Şapoval, Oleg; Belenciuc, Alexandr; Dmitroglo, Liliana; Bercu, Elena; Rusu, Marin; Vatavu, Sergiu
STUDY OF RECOMBINATION MECHANISMS IN CRYSTALS GaSe DOPED WITH Cu, Cd AND Sn
(2005) Evtodiev, Igor; Cuculescu, Elvira; Rusu, Marin; Caraman, Mihail
The stratified crystals of GaSe type serve as the basic element in different optoelectronic devices such as the micro lasers (the excitation with the electron beam), optoelectronic modulators for a large domain of wavelengths [1]. In order to enlarge the domain of application of gallium monoselenium and of analogical compounds by the structure and physical mechanical properties (GaS and InSe) it is necessary to increase the variety of characteristic physical properties of these compounds. The studies of optical properties and photoelect rical ones of the crystals GaS, GaSe and InSe pure nondoped prove that on their base the optoelectronic devices can be elaborated for the visible range and the near IR. In order to reach the conquerable parameters with the existent elaborations (on the base of semiconductors AIIBVI, AIIIBVI) it is neessary to vary controllably with the diagram of localized states in the forbidden band of these crystals. It is known [2] that the impurity atoms in the crystals of GaSe type, after the liquidation of structural defects in the sub grid of the metal from the interior of stratified packages Hal-M-M-Hal are localized in the space among the planes of the neighbor packages contributing so to the increasing of cohesion force among packages. These atoms will be situated on the surface of cleaving on the direction perpendicular to C contri buting so to the formation of the ionized surface states. The physical properties of the extra fine monocrystalline films are modified by the surface states in which the characteristic properties of the structures with the reduced sizes are manifested.
ZnO/CdS/CuGaSe 2 SOLAR CELLS – ABSORBER AND DEVICE PROPERTIES
(2006) Rusu, Marin
For solar cells based on CuGaSe 2 (CGSe) polycrystalline thin films, a novel chemical close-spaced vapor transport technique is used to deposit CGSe absorber. Film characterisa-close-spaced vapor transport technique is used to deposit CGSe absorber. X-ray fluorescence and elastic recoil detection analysis has been carried out. Optical measurements were performed to monitor the changes in the CGSe band gap as a function of com-rements were performed to monitor the changes in the CGSe band gap as a function of composition. These results are used for a discussion of the behaviour of the ZnO/CdS/CuGaSe2 solar cell photovoltaic parameters as well as of the current transport. For the first time, a thermally activated Shockley-Read-Hall recombination mechanism is observed for the CGSe-based solar cells in a large temperature region.