Facultatea de Fizică şi Inginerie / Faculty of Physics and Engineering
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Item Chemical method for the gallium arsenide rectification structure divide into crystals [Articol](UTM, 2009-10-01) Baranov, Simion; Cinic, Boris; Dudca, Tudor; Suman, VictorThis investigations are referred to power semiconductor devices (PSD) area manufactured by gallium arsenide (GaAs) advanced technology. The work’s objective is excluding the break-down effect on the p-n junction surface of high voltage devices, which is advance progressed with diminishing the crystal dimensions in the dividing process of the semiconductor structures. We propose the method of the GaAs deep etching by a mixture utilizing concentrated acids as nitric and hydrochloric acids in equal rates. After 30 min of mixing up the solution formation is consorted of the endothermic reaction, bound up by nitrosyl chloride (NOCl) formation, which dissolves the GaAs decomposed product in solution by arsenic oxidation up to As(V), forming ortoarsenic acid and gallium chloride. This method is used for dividing semiconductor structure of GaAs with 0.4-0.6 mm of thickness in small dimensioned crystals. The advantages of this technology are the great speed of GaAs dissolving, low costs of manufacturing and profitableness.Item Method of study gallium and arsenic losses in technology of gallium arsenate obtained from wastes [Articol](2005) Baranov, Serghei; Redwing, Joan; Bogdevici, Oleg; Cinic, Boris; Izmailov, DenisHaving the goal to recover gallium (Ga) and arsenic (As) from technological wastes derived from the process of growing epitaxial gallium arsenide structures, it is proposed to extract gallium arsenate (GaAsO4) by precipitation and filtration of the sediment. In this paper it is proposed to measure the concentrations of Ga and As by means of the atomic absorption spectrometer AAnalyst 800 directly in the filtrate solution. We compare the results obtained by two methods of elemental Ga and As atomization: flame and thermal atomization. The values of Ga and As concentrations in filtrate are function of pH for solutions containing 1- 680 mg/1 of Ga and 55-880 mg/1 of As. The developed method can be used to study and further optimize the technological process.Item Gallium arsenate removal from waste waters [Articol](2005) Baranov, Serghei; Cinic, Boris; Redwing, Joan; Stăvilă, VitalieThe aim of this paper is to study the loss of gallium (Ga) and arsenic (As) loss during the sedimentation of gallium arsenate (GaAsO4 ) from waste solutions of GaAs epitaxial production by chloride method. The solid wastes of this semiconductor manufacturing process are removed from technological equipment by dissolution in an acidic etching solution. In order to recover valuable Ga and very toxic As from these waste solutions we proposed to precipitate them as gallium arsenate. Experiments have been conducted to determine the migration of the two elements in filtrate and washing solutions as a function of pH for both model and real industrial wastes. It has been determined the optimal interval of pH for sedimentation, the losses of Ga and As present 0,01-0,053%. For model solutions the sedimentation is optimal in the range of pH from 3,2 to 4,3, while in the case of real waste solution this interval is 3,6-5,0. Comparative evaluation of the precipitation efficiency revealed that for model solutions the arsenic loss during the precipitation is higher (0,5%), and this can be explained by a different ratio of initial Ga3+ and AsO43- in model and real solutions. The results described in this paper provide important guidelines for the sedimentation of gallium arsenate from acidic waste solutions and indicate an overall efficiency of the process that could lead to savings in cost and process time for industrial effluent treatment technologies.Item Aero-ZnS architectures with dual hydrophilic-hydrophobic properties for microfluidic applications [Articol](2020) Pleșco, Irina; Braniște, Tudor; Wolff, Niklas; Gorceac, Leonid; Duppel, Viola; Cinic, Boris; Mishra, Yogendra Kumar; Sarua, Andrei; Adelung, Rainer; Kienle, Lorenz; Tighineanu, IonHere, we report on a new aero-material, called aero-ZnS, representing self-organized architectures made of ZnS hollow micro-tetrapod struc- tures with nanoscale thin walls. The fabrication process is based on the hydride vapor phase epitaxy of CdS on sacrificial micro-tetrapods of ZnO with simultaneous or subsequent transformation of CdS into ZnS and removal of the sacrificial ZnO crystals. The nanostructure of the obtained ZnS hollow micro-tetrapods exhibits the polytypic intergrowth of wurtzite- and sphalerite-type phases perpendicular to their close packed planes. The inner surface of the micro-tetrapod walls preserves oxygen sites, as demonstrated by imaging based on electron energy- loss filtering. The self-organized aero-ZnS architecture proves to be hydrophilic under tension and hydrophobic when compressed against water. Self-propelled liquid marbles assembled using ZnS hollow micro-tetrapod structures are demonstrated.Item CdS nanometric layers grown on SnO2 coated glass substrates for photovoltaic devices [Articol](2012) Botnariuc, Vasile; Gorceac, Leonid; Coval, Andrei; Chetruș, Petru; Cinic, Boris; Raevschii, Simion; Micli, ValdecCdS 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.Item Proprietăţile electrice ale celulei fotovoltaice cu joncţiune reliefată fabricată prin HVPE [Articol](Editura "Tehnica-UTM", 2014-10-22) Baranov, Simion; Gorceac, Leonid; Cinic, BorisIn this report we are represented the electro-physical properties of the photovoltaic cell with single relief junction fabricated on gallium arsenide substrate by HVPE method. This cell have the shunt resistance of 3.8 time bigger then the plane one, that it demonstrates the decrease of energy losses on the cell surface. It increases the efficiency of charges gathering (78 % of the full coefficient). It was used the AFM and RAMAN methods of investigation.Item Fotodetector pe heterojoncțiune din fosfură de indiu [Articol](CEP USM, 2020) Gorceac, Leonid; Botnariuc, Vasile; Coval, Andrei; Vatavu, Sergiu; Cinic, Boris; Raevschi, Simion; Rotaru, CorneliuItem Straturi nanometrice SnO2 pentru structuri fotovoltaice [Articol](CEP USM, 2014) Botnariuc, Vasile; Gorceac, Leonid; Cinic, Boris; Inculeţ, Ion; Raevschi, SimionItem 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, 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 Dispozitive din fosfură de indiu bazate pe efectul fotovoltaic [Articol](CEP USM, 2021) Botnariuc, Vasile; Gorceac, Leonid; Coval, Andrei; Vatavu, Sergiu; Cinic, Boris; Rotaru, Corneliu; Raevschi, SimionHomo- și heterojoncțiunile din p - InP și n - CdS au fost confecționate aplicând metoda epitaxiei din faza gazoasă în volum deschis, în sistem de cloruri, metoda HVPE (Hydride Vapour Phase Epitaxy) și tehnologia în volum cvasiînchis, în hidrogen. S-a stabilit că eficiența celulelor fotovoltaice pe bază de heterojoncțiuni n+CdS-p-p+InP cu suprafața fotoactivă de 3 cm2 și pe homojoncțiuni n+- p- p+InP (1 cm2) constituie 12% și,respectiv, 7,3% în condiții de iluminare standard, AM1 (1000 Wm-2). Eficiența cuantică externă maximală constituie 75-80% pentru heterojoncțiunea n+CdS - p- p+ InP și 70% pentru homojoncțiunea n+-p-p+InP în intervalul (600-900) nm al spectrului electromagnetic. Fotosensibilitatea absolută maximă de 0,51 A/W este caracteristică pentru heterojoncțiunea n+CdS - p- p+InP cu strat epitaxial intermediar(p = 6,51016 cm-3). Astfel de heterojoncțiuni pot fi utilizate pentru elaborarea fotodetectorilor în intervalul VIS.
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