C. Vasiliu

INCDO-INOE 2000, Research Institute for Analytical Instrumentation, Klausenburg, Cluj, Romania

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Publications (17)12.69 Total impact

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    ABSTRACT: Structural and morphological studies on Pulsed Laser Deposition (PLD) thin films based on phosphate glass doped with CdSe were performed. A KrF excimer laser was used to ablate thin films from CdSe target with oxide composition (wt. %): 70 P2O5-8 Al2O3- 19 Li2O- 3 CdSe. The films were deposited on silicon wafers by varying two parameters (laser energy and the temperature of Si substrate): a) high vacuum and Ts=20 °C; b) high vacuum and Ts=200 °C; c) high vacuum and Ts=20 °C at lower laser energy and d) high vacuum and Ts=200 °C at lower laser energy. Micro-Raman and FTIR spectroscopy analysis were undertaken to investigate the structural properties of the deposited films. The chemical characterization and the morphology of the films were performed by Energy Dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). In order to perform a satisfactory reproducibility of the stoichiometry between the films and the vitreous target, the deposition parameters were modified appropriately. Analyzing the EDX spectra and the obtained SEM mapping images, a good elemental chemical uniformity of the PLD films were observed.
    No preview · Article · Nov 2013 · Chalcogenide Letters
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    ABSTRACT: Two series of potassium phosphate glasses have been prepared, AG2 compositions containing P 2O 5, K 2O, MgO with B 2O 3, Fe 2O 3, ZnO, MoO 3 and AG3 compositions containing P 2O 5, K 2O, MgO, CaO with B 2O 3, Fe 2O 3, ZnO, MoO 3, MnO 2. The glasses have been prepared by a conventional route: (i) preparation of raw materials; (ii) melting and refining; (iii) fritting; (iv) grinding of the glass; (v) screening of glass powder. Both for AG2 and AG3 glasses, FTIR spectra recorded in the 400-4000 cm -1 range, revealed optical phonons specific for the phosphate matrix. In the case of AG2.1 and AG3.1 glasses containing B 2O 3, FTIR spectra put in evidence optical phonons specific for B-O bond from BO 3 and BO 4 units. Raman spectra, recorded in the 100-4000 cm -1, by 785 nm laser excitation show stretching vibration modes specific for phosphate matrix together with Mg-O vibration mode in the 320-336 cm -1 range. Information about vitreous fertilizers solubility was achieved by conduct-metric method. For AG2 series, minimum solubility was measured for the sample containing iron oxide and maximum solubility for base sample. From AG3 series, the sample containing iron oxide also showed minimum solubility, but the maximum solubility appeared for the sample with molybdenum oxide.
    Full-text · Article · Nov 2011 · Journal of Optoelectronics and Advanced Materials
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    ABSTRACT: Undoped and neodymium doped quartz glasses were obtained by the hybrid sol-gel method. The vitrification was performed in He atmosphere. The Nd3+characteristic absorption bands in the UV and VIS were put into evidence. Investigations in the NIR range revealed a small amount (86 ppm) of OH- in the vitreous matrix. FTIR and Raman spectra exhibit the SiO2 glass characteristic vibrations and also the characteristic vibrations of Si-OH and Si-Cl bonds. The photoluminescence peaks at 640, 920 and 1080 nm belonging to the Nd3+ doped quartz glass were evidenced.
    No preview · Article · Oct 2010 · OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS
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    ABSTRACT: The paper reports a study on lithium phosphate glasses, containing calcium or magnesium and ferric/ferrous oxides. Iron oxides provide high chemical stability against water and enhance the glass capacity to embed different chemical compounds. The wet synthesis method provides an enhanced homogeneity of the glass batch and improves the optical quality of the glass samples. FTIR and Raman spectroscopy revealed the network former role of P2O5 as well as the modifier/former role of iron. The vibration mode shifted at 1250 cm-1 is attributed to the iron that enters into the phosphate network, forming Fe-O-P bonds instead of P-O-P bonds.
    Full-text · Article · Sep 2010 · OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS
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    ABSTRACT: Introduction Experimental Results and Discussion Conclusions Acknowledgements
    No preview · Article · Dec 2009
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    ABSTRACT: Thin films of complex oxides have been obtained by pulsed-laser deposition (PLD) from glass targets belonging to the system Li(2)O-Al(2)O(3)-P(2)O(5)-(RE)(2)O(3), with RE = Nd, Pr, Er. The films were deposited on quartz, silicon and ITO/glass substrates using a F(2) laser (lambda = 157 nm, iota approximate to 20 ns) for ablation in vacuum. The structural, morphological and optical properties of the oxide films were investigated through IR and UV-VIS spectroscopy, Atomic Force Microscopy (AFM), Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy (SEM-EDX) and Spectroscopic Ellipsometry. The laser wavelength was found to be the key parameter to obtain thin films with very smooth surface. In this way new possibilities are opened to grow multilayer structures for photonic applications. (C) 2008 Elsevier B. V. All rights reserved.
    Full-text · Article · Mar 2009 · Applied Surface Science
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    ABSTRACT: Thin films of phosphate glasses were prepared by pulsed laser deposition in oxygen atmosphere on ITO-coated glass and silicon substrates respectively, using a Nd:YAG laser (266 nm). The targets were Li2O–Al2O3–P2O5 bulk glasses doped with Pr and Nd. Infrared transmission-, energy dispersive X-ray- and X-ray photoemission spectroscopy investigations carried out on targets as well as on the deposited films proved a satisfactory compositions transfer on both substrates. Scanning electron microscopy and atomic force microscopy show continuous films with glassy spheres. Processes where substrates were positioned perpendicularly to targets produced discontinuous drops free films.
    Full-text · Article · Jan 2009 · Journal of Materials Science Materials in Electronics
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    ABSTRACT: Thin films in the SiO2-P2O5 system are intensely studied due to their applications in microelectronics, sensing, nano-photonics, optoelectronics and as ionic conductors. Sol-gel is the most used method for preparation of such films. Previous studies established the very low reactivity of the phosphorous alkoxides and the high tendency of the phosphorous oxide to volatilize at thermal treatment. In order to identify the most appropriate precursor for obtaining layers with desired composition and properties a systematic study of the sol-gel film preparation using different phosphorous precursors was carried out. The films were deposited on glass and ITO/SiO2 coated glass substrates at room temperature. To check the influence of the type of precursors on the films thermal stability and properties a post deposition annealing was performed at low temperatures in the range 150-200°C. The film characterization was performed using various techniques as Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric an thermodifferential analysis (DTA/TGA), X-ray Photoelectron Spectroscopy (XPS), Spectroscopic Ellipsometry (SE), Atomic Force Microscopy (AFM). The P evolution during the drying process was determined in the films obtained with P-alkoxides. Only in the films obtained with H3PO4 the P could be detected after thermal treatment at 200°C. This result could be explained by the fact that the phosphorous component is not chemically bonded in the matrix, but only embedded and so, it can be easily evaporated from the film during the XPS analysis.
    No preview · Article · Jan 2008 · Ceramic Engineering and Science Proceedings
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    ABSTRACT: The investigated ecological glasses with no toxic compounds, such as BaO, PbO, As2O3, As2O5, fluorine, CdS and CdSe in their composition are located in ternary and quaternary oxide systems: ZnO-SiO2-TiO2 and SiO2-R′2O- R″O-R‴O2, where R′ is Na or K, R″ is Ca or Mg and R‴ is Zr or Ti. The first system contains P2O 5, ZnO and TiO2 in order to obtain opal glasses, without fluorine compounds. The second system replaces the barium oxide and lead oxide with potassium, magnesium, zirconium and titanium oxides, for materials like lead free crystals. The raw materials can be replaced by silicate or borosilicate glass waste. The advantages of borosilicate glass waste are: bringing valuable components into recipes (B2O3, CaO, Al2O3), saving raw materials and energy, creating an ecological environment The characteristic temperatures (vitreous transition point, low and high annealing points, softening point) and the thermal expansion coefficient of the glass are presented. The FTIR and Raman spectroscopy provided structural data, such as characteristic vibration maxima for silicon and titanium oxide, and revealed the role of zinc oxide in the vitreous network. The refraction index and UV-VIS transmission are discussed.
    No preview · Article · Jan 2008 · Advanced Materials Research
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    ABSTRACT: Thin films of complex oxides have been deposited by pulsed laser ablation, starting from glass targets. Glass oxide targets were prepared by a non-conventional wet method and consisted of a matrix having the composition: Li 2O, BaO, Al 2O 3, La 2O 3 and P 2O 5, respectively, non-doped and doped with Nd 2O 3. The films were deposited on silicon substrates using the fourth harmonic of a Nd:YAG laser (266 nm), in an oxygen background atmosphere. The influence of the deposition parameters on the morphological and optical properties of the oxide films was particularly investigated. IR absorption spectroscopy, optical microscopy, X-ray diffraction and atomic force microscopy were used to characterize the targets and the deposited thin films.
    No preview · Article · Jul 2007 · Applied Surface Science
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    ABSTRACT: Polyaniline (PAni) has important electro-conductive properties, high absorbance in microwave range and it is also frequently used in gas sensors because of its capability to convert chemical interactions into electrical signals. The methods of obtaining polyaniline in the form of thin films and/or nanostructures are complicated and request special physical and chemical treatments, both on the substrate surface and for the polymer itself.In this paper we applied matrix assisted pulsed lased evaporation (MAPLE) for obtaining thin films and nanostructures of polyaniline. In MAPLE, the target consisting of the material (usually 0.2–3 wt%) dissolved in a solvent is frozen and it is evaporated using a laser. In our case polyaniline–emeraldine salt (PAni–ES) was dissolved in xylene or toluene, frozen in liquid nitrogen and was used as target. The third and the fourth harmonics of a Nd–YAG laser (λ = 355 nm and 266 nm) were used as laser sources. The obtained films have been characterized by atomic force microscopy, dielectric spectroscopy and Fourier transform infrared spectroscopy. The influence of the solvent type and of the laser parameters (wavelengths and fluence) on the polyaniline structures composition and properties has been investigated.
    Full-text · Article · Jul 2007 · Applied Surface Science
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    ABSTRACT: Thin films in the SiO2-P2O5 system are intensely studied due to their applications in microelectronics, sensing, nano-photonics, optoelectronics and as ionic conductors. Sol-gel is the most used method for preparation of such films. Previous studies established the very low reactivity of the phosphorous alkoxides and the high tendency of the phosphorous oxide to volatilise at thermal treatment. In order to identify the most appropriate precursor for obtaining layers with desired composition and properties a systematic study of the sol-gel film preparation using different phosphorous precursors was carried out. The films were deposited on ITO/SiO 2 coated glass substrates at room temperature. To check the influence of the type of precursors on the layers thermal stability and properties a post deposition annealing was performed at temperatures of 150 and 200°C. The film characterization was carried out using various techniques as Spectroscopic Ellipsometry (SE), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR).
    No preview · Article · May 2007 · Journal of Optoelectronics and Advanced Materials
  • M. Elisa · C. Vasiliu · J. Striber · D. Radu · J. H. Trodahl · M. Dalley
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    ABSTRACT: Aluminophosphate glasses doped with semiconductor CdSxSe 1-x crystallites were produced by a wet non-conventional method that provides a high optical homogeneity of the glass. The samples belong to the oxide systems: Li2O-BaO-Al2O3-La 2O3-SiO2-P2O5 (SDG1) and Li2O-Na2O-BaO-Al2O3-La 2O3-SiO2-P2O5 (SDG2) to which we added CdS0.5Se0,5 1 % wt. (0.9 % mol.) and ZnO 1 % wt. (1.5 % mol.). The UV-VIS-NIR transmission spectroscopy revealed the shift of the transmission edge, depending on the temperature and the duration of annealing. As a general trend, the higher the temperature and the duration of the annealing process the more significant the shift of the transmission edge to higher wavelengths in the visible range. Consequently, the glass changed from colourless to red that indicates the presence of CdS0.7Se 0.3 crystallites in the vitreous phosphate matrix, as also indicated by transmission electron microscopy analysis (TEM). Raman spectra obtained by Ar+ laser excitation at 514.5 nm, showed first and second order scattering lines from CdS0.7Se0.3. The device SPIRICON LBA 300 provided information regarding the dispersal of the crystallites in the host aluminophosphate glass. Thus, by a diode laser excitation at 625 nm, we analyzed relative intensity profile of the emergent beam from the doped-glass samples and we were able to estimate the crystallites dispersal in these vitreous materials.
    No preview · Article · Apr 2006 · Journal of Optoelectronics and Advanced Materials
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    ABSTRACT: Aluminophosphate glasses doped with CdSxSe1-x have been produced by a wet nonconventional method that provides a better homogeneity of the glass matrix. The glass samples belong to the oxide systems: Li2O–BaO–Al2O3–La2O3–SiO2–P2O5 and Li2O–Na2O–BaO–Al2O3–La2O3–SiO2–P2O5. The band gaps of the doped samples were determined by UV-VIS-NIR transmission spectroscopy, using the dependence of the absorption coefficient on photon energy. Structural investigations on semiconductor doped glasses were performed by infrared absorption and Raman spectroscopy. Infrared absorption spectra revealed structural units of the phosphate glass matrix. Raman spectra obtained by excitation with 458 and 514 nm revealed CdS0·696Se0·304 peaks and by excitation with 325 nm, revealed the phosphate matrix bonds. Transmission electron microscopy, selected area electron diffraction (SAED) and fluorescence spectroscopy were used to investigate the semiconductor doped glasses. SAED patterns allowed the calculation of the composition and consequently the band gap of the CdSSe crystallites embedded in the glass matrix. A strong CdSSe fluorescence was observed, indicating well ordered crystallites with a molar fraction of S and Se close to 0·5 as intended.
    No preview · Article · Nov 2005 · Physics and Chemistry of Glasses
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    ABSTRACT: Summary form only given. We present a review of the research carried out during the past six months by groups from Romania, Victoria University of Wellington, New Zealand, and Universite de Provence, Marseille, France, with the aim to fabricate photonic materials within the framework of the COST ACTION P11. Novel aluminophosphate glasses doped with semiconductors (CdSSe) have been produced, whose transmission in the visible and Raman spectra have been investigated. We have noticed that transmission edge and the spectra shape depend on the crystallites' dimensions. The fluorescence is relatively narrow (0.12-0.15 eV) suggesting reasonably well-ordered crystallites with reasonably uniform diameters. Another attempt of the groups to find a way of producing quasi-periodic, at this stage, features, in amorphous materials, consists of annealing studies on amorphous GaN thin films (150 nm) on silicon. The annealing processes have been carried out using the hot stage of an electronic microscope (SEM), so that real time observation has been possible. Following the annealing, the GaN films have developed hemispherical structures uniformly distributed over the entire surface of the sample. Apparently, those structures are denser than the surrounding film, and EDX analysis shows that they conserved the initial composition of the film. At the necked eye the colour of the sample changed from blue to yellow.
    No preview · Conference Paper · Aug 2004
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    ABSTRACT: This paper reports on some optical properties of phosphate glasses doped with Cd(SSe), prepared by a non-conventional wet-route, The glass samples belong to the following oxide systems: Li2O-P2O 5Al2O3-BaO-SiO2-La2O 3 Li2O-Na2O-P2O5-Al 2O3-BaO-SiO2-La2O3 to which we added CdS0,5Se0,5 1 % wt. and 1 % ZnO wt. The optical properties of our materials were investigated by transmission in the visible range, photoluminescence and Roman spectroscopy. The absorption spectra in the IR range provide information on the structure of the doped glasses while transmission electron microscopy reveals the shape and the average size of the dopant crystallites.
    No preview · Article · Jan 2003
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    ABSTRACT: Vanadium and vanadium-cerium oxide gels and films obtained by the sol-gel method have been widely studied, due to their catalytic, electrochemical, electronic and ionic properties, a result of their ability to form combinations in more than one valent state. V and V-Ce oxide powders were prepared by sol-gel method in the presence and absence of polyols. An organic alkoxide precursor was used to obtain V 2 O 5 , while in case of the binary product, the alkoxide preparation route was compared with an aqueous one. The powders were characterized by transmision electron microscopy (TEM), infrared spectroscopy, X-ray diffraction and by thermal analysis. The obtained V 2 O 5 powders crystallized in the micrometric range. In case of the binary product, the CeO 2 addition led to a nanometric quasi-crystallised product.
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Publication Stats

53 Citations
12.69 Total Impact Points

Institutions

  • 2009-2011
    • INCDO-INOE 2000, Research Institute for Analytical Instrumentation
      Klausenburg, Cluj, Romania
  • 2007
    • The National Institute of Materials Physics
      Măgurelele, Prahova, Romania
  • 2005
    • Institute of Optoelectronics
      Essen, North Rhine-Westphalia, Germany