Browsing by Author "Chetruș, Petru"

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ABOUT THE EDGE LUMINESCENCE OF CADMIUM SULPHIDE THIN LAYERS GROWN ON MOLYBDENUM
(Institute of Electrical and Electronics Engineers, 1995-11-11) Raevschi, Simion; Gorceac, Leonid; Coval, Andrei; Chetruș, Petru
CdS 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.
ASPECTE PRIVIND FORMAREA INIŢIALĂ A TINERILOR PEDAGOGI DE CHIMIE ÎN CONTEXTUL REFORMELOR EDUCAŢIONALE
(CEP USM, 2009) Velișco, Nadejda; Dragalina, Galina; Kudrițkaia, Svetlana; Revenco, Mihai; Chetruș, Petru
A short analysis of the expertise of the Department of Chemistry and Chemical Technology concerning the initial formation of the young teachers of chemistry is presented in the light of the Bologna's Convention requirements. The formation is undertaken, following the main steps of the chemical education: fundamentals of chemistry - pedagogical education- teaching methodology- pedagogical practice- License Diploma and post university training. The place of the new aspects such as ecology, use of computer, skills of modeling etc. in university program of the first cycle is discussed.
(BENZOYLFORMALDEHYDE OXIMATO-j2N,O)- (BENZOYLFORMALDEHYDE OXIME-jN)- CHLORIDOPLATINUM(II)
(2007) Cucușchin, Nicolae; Chetruș, Petru; Haukka, Matti
In the title complex, [Pt(C 8H 6NO 2 )Cl(C 8H 7NO 2)], the Pt II centre is coordinated by a monodentate and an N,O-chelating deprotonated benzoylformaldehyde oxime and a Cl atom. There is an intramolecular N—OH—O hydrogen-bonding system between the oxime OH group and the oximate O atom.
CdS NANOMETRIC LAYERS GROWN ON SnO2 COATED GLASS SUBSTRATES FOR PHOTOVOLTAIC DEVICES
(2012) Botnariuc, Vasile; Gorceac, Leonid; Coval, Andrei; Chetruș, Petru; Cinic, Boris; Raevschii, Simion; Micli, Valdec
CdS layer thickness decreases at high substrate temperatures due to the fact that a part of CdCl2/(NH2)2 CS aqueous solution evaporates without reaching the substrate surface. CdS layers deposited at the substrate temperature from 250oC to 450oC are growing with a deficit of sulfur. CdS layers with better stoichiometry were grown in the conditions when in the solutions, used for CdS layers growing, there is an excess of thiourea (CdCl2/ TU =1:2). The high charge carrier concentration of 1020cm-3 in CdS layers grown on glass substrates coated with SnO2 layer is related to Sn doping of the layers from SnO2 layer.
COERENŢA ÎNVĂŢĂMÂNTULUI ŞI CERCETĂRII ŞTIINŢIFICE: ŞCOLI DOCTORALE
(CEP USM, 2007) Todos, Petru; Muraru, Elena; Chetruș, Petru
The research learning and the development of the researcher's career, the necessity of candidates for a doctor's degree and good professional scientists become one of the most important discussed themes, on the level of European research scientific ability and it's consolidation and the professional development of the European Area based on knowledge.
CURRENT FLOW MECHANISM IN ZnSe-ZnO-Pd STRUCTURES
(CEP USM, 2010) Scurtu, Roman; Gașin, Petru; Chetruș, Petru
Structurile MOS au fost obţinute folosind ca suporturi plăcuţe monocristaline de ZnSe orientate în direcţia [110] cu grosimea 3-5mm. Monocristalele de ZnSe au fost tratate în zinc +0,1%Al la 950ºC timp de 100 ore, în vid. Concentraţia electronilor la 300 K este de 1,85x1016cm-3, iar mobilitatea – 466 cm2 /VS. În calitate de oxid s-au folosit straturi subţiri de ZnO, obţinute prin tratarea cristalelor de ZnSe în apă oxigenată. Grosimea stratului de ZnO depinde de timpul de tratare chimică şi alcătuieşte 4-13 nm. Contactul metalic, strat subţire din Pd, a fost obţinut prin evaporare termică în vid. Ca contact ohmic la cristalele de ZnSe s-a folosit In obţinut prin tratare în aer la 370ºC timp de 30-120 sec. La polarizări directe, curentul depinde exponenţial de tensiunea aplicată şi, la tensiuni de până la 0,7 V, e determinat de curentul de tunelare, iar mai mare de 0,7 V – de procesele de recombinare. Factorul de idealitate variază de la 2,86 –la 93 K la 1,47 – la 333 K. Potenţialul de difuzie variază între 0,8 V şi 1,28 V, corespunzător la 353 K şi 113 K. La polarizarea inversă este o funcţie de putere şi are factorul de putere 3,93 la 113 K şi de 2,42 la 353 K. La polarizări directe 2÷3 V şi T=77 K structurile Pd-ZnO-ZnSe radiază în regiunea albastră. La 77 K se observă două fâşii: prima mai intensivă, cu maximul 2,7 eV, şi alta – cu maximul 2,06 eV.
DISTRIBUŢIA IMPURITĂŢII DE Ga ÎN CRISTALELE PbTe CRESCUTE PRIN METODA DE SUBLIMARE ZONALĂ
(Universitatea de Stat „Alecu Russo“ din Bălţi, 2015) Nicorici, Valentina; Chetruș, Petru; Nicorici, Andrei
În lucrarea dată sunt prezentate rezultatele cercetărilor fenomenelor de transport în calcogenidele de plumb dopate cu Ga (NGa= 0,5 at. %) în procesul de creştere prin metoda sublimării zonale. Eşantioanele studiate spre deosebire de cristalele PbTe nedopate aveau conductibilitate electrică de tip n. Lungimea cristalelor crescute a fost de 5- 6 cm, avînd concentraţia electronilor de la 2,7·1019 сm-3 (segmentul iniţial) pînă la 6,4·1018 сm-3 (segmentul final). În eşantionul cu NGa= 0,5 at.% concentraţia electronilor practic nu depinde de temperatură, ceea ce este legat cu fixarea nivelului Fermi. Cristalele au fost supuse tratamentului termic (la 5400С şi la 6500С) cu cercetarea intermediară a proprietăţilor galvanomagnetice. Tratarea la 5400С duce la micşorarea concentraţiei purtătorilor de sarcină cu 2-3 ordine de mărime (pînă la 1,4·1016 сm-3) şi creşterea mobilităţii lor pînă la 3.104 сm2/V·s (la 80К). Tratarea la 6500С modifică tipul conductibilităţii electrice din n- în p-tip şi micşorează mobilitatea purtătorilor de sarcină pînă la ~ 9000 cm2/V·s.
ELECTRICAL AND PHOTOELECTRICAL PROPERTIES OF HETEROJUNCTIONS ON THE BASE OF Cu(InGa)Se2
(2005) Chetruș, Petru; Gașin, Petru; Nicorici, Valentina; Suman, Victor
CdS films deposited by hot wall technique on mica were used as substrates for Cu(InGa)Se2 deposition. Two methods were used for the deposition of Cu(InGa)Se2 films: a) vacuum thermal evaporation from a single source and b) “flash” evaporation. The obtained films were of p-type conductivity with hole concentration varied from 2×1018 cm-3 to 6×1020 cm-3 depending on the fabrication method. The structures Cu(InGa)Se2–CdS were divided into two groups: the structures of type I having the CdS film thickness from 1.6 m to 2.8 m and the structures of type II having the CdS film thickness from 0.6 m to 0.8 m. It was established that the direct/reverse current ratio is 8-16. For the first type heterostructures the diffusion potential is 1.2–1.8 V and for the second type is 0.2–0.34 V. The Cu(InGa)Se2–CdS fotosensitivity is situated in the wavelength region from 0.51 m to 1.1 m and is determined by the electron-hole pair generation in both materials.
LUMINESCENT PROPERTIES OF ZnS SINGLE CRYSTAL ANNEALED IN THE V th GROUP ELEMENTS MELT
(2006) Sobolevscaia, Raisa; Corotcov, Vadim; Bruc, Leonid; Sușchevici, Constantin; Chetruș, Petru
The influence of ZnS single crystal annealing in the media based on V-group elements Bi and Sb on its photoluminescent (PL) properties was studied. The following media: Bi, Sb, Bi+Zn, Sb+Zn, Bi+S, Sb+As and Bi+Al were used for the annealing.Two types of the starting crystals were used: I) low resistivity ZnS; II) high resistivity ZnS. The annealing was carried out in the vacuumed silica ampoules at the temperatures of 1400 K (I) and 1200 K (II) during 100hrs. The obtained results show that ZnS crystals annealing in Bi and Sb melts leads to the analogical reorganization of radiation centers based on the native and impurity defects generated by interphase interaction at ZnS-melt interface. These defects are responsible for the appearance of the green radiation having the feature of intracentred transitions. The high value of green band half-width indicates that it is a superposition of a few bands. These could be a PL bands related to the oxygen presence, the impurity centers of the V group elements and to V S .
NANOLAMELLAR STRUCTURES OF OXIDE-AIIIBVI:Cd SEMICONDUCTORS TYPE FOR USE AS DETECTORS OF RADIATION IN THE UV SPECTRAL REGION
(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.
O NOUĂ ETAPĂ ÎN MODERNIZAREA ÎNVĂŢĂMÂNTULUI PREUNIVERSITAR LA CHIMIE
(CEP USM, 2007) Dragalina, Galina; Chetruș, Petru; Velișco, Nadejda; Kudrițkaia, Svetlana
Ce matériau scientifique et méthodique décrit les étapes du développement de l’enseignement de la chimie, de la reforme curriculaire, les types d’élaborations et d’implantations, qu’ ont réalisées dans la période des années 1995-2007 les membres du groupe de création „Chimcont” à la Faculté de Chimie et Technologie Chimique de l’Université d’Etat du Moldova, y compris les manuels scolaires pour les cycles gymnase (les classes VII-IX) et lycée (les classes X-XII), les guides pour les professeurs et autres
PHOTOELECTRICAL PARAMETERS OF nCdS–pCdTe THIN-FILM SOLAR CELLS WITH A CdO BUFFER LAYER
(2016) Gașin, Petru; Gargara, Ludmila; Chetruș, Petru; Inculeț, Ion; Fiodorov, Vladimir; Qassem, Amjad-Al
The results of the studies of the effect of a CdO buffer layer on the photoelectrical parameters of CdS–CdTe solar cells have been described. It has been found that the formation of a 5–8 nm thick CdO buffer layer leads to an increase in the CdS–CdTe solar cell open circuit voltage (Voc) by 90–140 mV, short circuit current (Isc) by 1.4–3.2 mA/cm2, and efficiency by 2.8–4.1% at 300 K and an illumination of 100 mW/cm2.
PROPRIETĂŢI ELECTROFIZICE ALE STRATURILOR DE CdS OBŢINUTE PRIN METODA PULVERIZĂRII CU TRATARE TERMICĂ ÎN HIDROGEN
(CEP USM, 2012) Botnariuc, Vasile; Gorceac, Leonid; Coval, Andrei; Cinic, Boris; Chetruș, Petru; Raevschi, Semion; Banu, Simion
Prin metoda pulverizării chimice au fost crescute straturi de CdS din soluţii apoase de CdCl2/(NH2)2 CS cu molaritatea de 0,1 M în intervalul de temperaturi (250...450)°C. Straturile au fost tratate termic în flux de hidrogen timp de 20 min la temperaturile de 350 şi 450°C. Au fost cercetate proprietăţile electrofizice şi fotoluminescenţa acestor straturi. În straturile depuse la 450°C cu mărirea temperaturii de tratare până la 450°C se observă o uşoară micşorare a concentraţiei purtătorilor de sarcină. Spectrul fotoluminescenţei prezintă o fâşie largă în intervalul de energii 1,6...2,6 eV. Se observă un vârf al fotoluminescenţei cu energia de 1,95 eV, care se deplasează cu mărirea temperaturii de creştere a straturilor de CdS şi atinge valoarea de 2,5 eV pentru straturile crescute la temperatura de 450°C.
STRATURI CdS CRESCUTE PE SUPORTURI DE STICLĂ PRIN METODA PULVERIZĂRII
(CEP USM, 2012) Botnariuc, Vasile; Gorceac, Leonid; Coval, Andrei; Chetruș, Petru; Cinic, Boris; Raevschi, Simion; Micli, Valdec
CdS layers were grown from aqueous solutions of cadmium chlorine (CdCl2) and thyourine (NH2)2 CS with the molarity of 0,1 M by pulverization method in the temperature range of (250...450)°C. CdS layers were grown on glass substrates covered with a previously deposited SnO2 layer. The deposited CdS layers morphology, atomic weight and composition were studied biasing a sunning electron microscope (SEM). The morphology, atomic weight and composition of the deposited CdS layers considerably changes with the increase of the deposition temperature. The charge carriers’ concentration and their mobility in CdS layers deposited at different temperatures were measured and estimated.
STRATURI NANOMETRICE DE STANAT DE CADMIU PENTRU CELULE FOTOVOLTAICE
(CEP USM, 2014) Botnariuc, Vasile; Gorceac, Leonid; Covali, Andrei; Cinic, Boris; Chetruș, Petru; Inculeț, Ion
Obiectivele acestei lucrări rezidă în stabilirea condiţiilor tehnologice optime de depunere a straturilor de stanat de cadmiu (Cd2SnO4) prin metoda pulverizării pe substraturi de sticlă şi de fosfură de indiu (InP) şi în studierea proprietăţilor elecrtofizice şi optice ale acestora. Straturile de stanat de cadmiu au fost depuse într-un flux de oxigen, din clorurăde cadmiu (CdCl2·2,5H2O)şi clorură de staniu (SnCl4·5H2O), dizolvate în alcool etilic cu molaritatea de (0,1-0,3)M, în intervalul de temperaturi (250...450)°C. Au fost cercetate proprietăţile electrofizice ale straturilor în dependentă de raportul componentelor CdCl2·2.5H2O şi SnCl 4·5H2O în soluţiile folosite la pulverizare şi de temperaturile de depunere. Studiul propriet ăţilor optice ale acestor materiale demonstrează că ele sunt transparente înintervalul 250....1300) nm. A fost demonstrată posibilitatea de creştere a oxizilor Cd2SnO4 prin etoda pulverizării şi de folosire a acestora ca straturi intermediare la structurile fotovoltaice pInP-nCdS.
THIN LAYER PHOTOVOLTAIC MODULES BASED ON CdS-CdTe HETEROJUNCTIONS
(2011) Fiodorov, Vladimir; Gașin, Petru; Gagara, Ludmila; Chetruș, Petru
A technology of thin layer photovoltaic modules with dimensions of 65 x 80 mm2 based on CdS-CdTe heterojunctions prepared via the quasi-closed volume technique was developed. The modules were made on a single glass plate; each element was positioned along the given plate so that the resulting module contains nine solar cells with an area of 3 cm2. The design of the module made it possible to study the energy parameters of each solar cell as well as the entire module. The study of the photovoltaic module based on CdS-CdTe heterojunctions showed the following parameters: short circuit current Isc = 270 mA; open circuit voltage Ucd = 0.786 V; FF =0.46, power discharged in the load Pmax ≈ 100 mW, and efficiency η ≈ 8.2% at the radiation power of 53 mW/cm2.