Stage 1 - P2 2017
The project implementation schedule
Phase no. 16
Responsible: Dr. B. SAVA, Dr. L. BOROICA
Title: "Proiectarea, modelarea, obtinerea, caracterizarea de straturi subtiri nanostructurate din materiale vitroase si vitroceramice boro-fosfatice dopate prin PLD"
Abstract: At this stage there were realized:
- A research - design study of doped boron - phosphate glasses for PLD targets;
- 2 models of oxide compositions for the doped boron - phosphate glasses for PLD depositions;
- 2 techniques for achieving and 2 types of boron - phosphate materials for PLD targets, one glassy, BP2, second glass-ceramic type, BP1;
- Two targets for boron - phosphate PLD depositions were obtained, from BP1 and BP2 materials;
- More than 20 samples of thin layers were obtained by PLD method on different substrates, in various working conditions.
Ablation processes and PLD were realized in a vacuum chamber made of stainless steel. As source for the ablation process a pulsed excimer laser with KrF (CompexPro 201-coherent) was used, operating at 248 nm with a repetition rate of 10 Hz and a pulse width of 20 ns.
The laser beam, after reflection in two mirrors, enters into the stainless steel vacuum chamber through a quartz window and is focused through a convergent lens on a rotating target at an angle of incidence of 60°, giving a rectangular profile at impact with the target. The substrate is positioned parallel to the target at a distance of 60-100 mm. The deposition chamber was vacuumed at a pressure around 10-7 mbar before starting the deposition process. The first samples were deposited at a pressure of oxygen of 10-3 mbar and a fluency of 2-3 J/cm2.
Depositions were conducted on boron silicate and quartz glass for 6 samples: 4BP1 and 2 BP2 at 600°C, substrate temperature. On another quartz substrate, thicker, they were carried out two other BP2 depositions at 400°C, substrate temperature.
The best results, in terms of surface of deposition roughness, were obtained for the temperature of substrate 400°C and vacuum of 3 x 10-6 bar.
AFM investigation of the quartz glass substrate showed in evidence a very smooth roughness of less than 1 nm.
AFM investigations showed that the temperature of the substrate influences the thickness of BP2 thin films obtained by PLD. Using AFM, we measured how thick the PLD deposited film was: at 400°C, the thickness was almost double then that deposited at 600 °C.
Surface roughness is affected also by the number of pulses. Surface roughness increases from 60 nm up to 150 nm at the temperature of the substrate of 400 °C, i.e. from 20 nm to 50 nm, at 600 °C, the temperature of the substrate, when the number of pulses is increased from 12500 to 25000.
Dissemination: Research results will be communicated to 3 international conferences in 2017:
- 19th International Sol-gel Conference, Liège, Belgium, 2-8 September 2017;
- 9th International Conference on Borates Glasses, Crystals and Melts, Oxford, England, 24-28 July 2017;
- 4th European Chemistry Congress, Barcelona, Spain, 11-13 may 2017.
A number of minimum 2 articles will be submitted for publication in peer-reviewed high ISI quoted journals such as Ceramics International and Applied Surface Science.
Phase no. 17
Responsible: Dr. A. STAICU
Title: "Obtinerea si caracterizarea emisiei de tip lasing de catre micropicaturi dopate cu nanoparticule"
Abstract: Studies on the emission spectra of microdroplets containing Rh6G solutions in water doped with TiO2 nanoparticles are reported. The excitation is made by the second harmonic of a pulsed Nd:YAG laser at 532 nm, pulse duration at half maximum 6 ns and energy varied between 6 and 10 mJ. The laser induced emission spectra are analyzed function of TiO2 concentration and pumping laser energy. Comparison between fluorescence dispersed spectra emitted by pendant droplets containing TiO2 nanoparticles with respect to Rh6G water solutions droplets pumped in the same conditions is made. The surface tension measurements of the samples show that with variation of dye and nanoparticles concentrations, surface phenomena take place and influence the behavior of the droplet fluorescence.
These studies show that TiO2 colloidal dispersions containing laser dyes in droplet have an influence on the dye emission properties which can be modulated by varying nanoparticles concentration and laser pumping energy. In this way, the TiO2 colloids can be useful in obtaining laser active media with tunable properties.
Phase no. 18
Responsible: Dr. A. PETRIS
Title: "Studiul neliniaritatii optice de ordinul trei a unor straturi subtiri pentru aplicatii in fotonica"
Abstract: ZnSe is a semiconductor of II-VI group, with many applications in photonics due to its broadband transmittance spectrum, large direct band gap Eg and high refractive index. The last property is of particular interest for the design of 1D and 2D thin film periodic structures where high refractive index contrast is essential. Material characteristics of ZnSe are suitable for all-optical devices for emission, transmission, processing and storage of information. The nonlinear optical phenomena excited by ultrashort laser pulses in nonlinear optical materials have a major impact in all-optical functionalities.
We studied the third-order nonlinear optical response in ZnSe thin films, which are of special interest for photonic applications, by third harmonic generation (λ=517 nm) with ultrashort laser pulses from an Er doped fiber laser (λ=1550 nm), exciting fast, non resonant (electronic) nonlinearities. The ZnSe thin films’ refractive index values at wavelengths of interest in third harmonic generation, are extracted from the Sellmeier equations derived from the experimental transmittance data. We measured the ultra low (∼ pW) third harmonic power with a common photo camera used as an ultra sensitive power meter. We have determined the ZnSe thin film films’ third-order nonlinear susceptibility, χ(3), and the nonlinear refractive index, n2, excited by a laser beam at λ=1550 nm, parameters that characterize the nonlinear optical response of the studied material with high impact on photonics and optical communications.
Phase no. 19
Responsible: Dr. Eniko GYORGY
Title: "Investigarea activității fotocatalitice a nanomaterialelor compozite alcatuite din oxizi ale metalelor de tranzitie si nanoparticule de carbon"
Abstract: Titanium dioxide nanoparticles (TiO2 NPs) - graphene oxide (GO) composite films were deposited by spin coating technique onto SiO2 quartz substrates. TiO2 NPs and GO platelets were used as base materials for the preparation of the starting water/acetone dispersions. Polystyrene (PS) buffer layers were deposited by drop-cast method onto the substrates surface to ensure the adherence of the TiO2-GO composite layer. The morphological and physico-chemical properties of the composite materials have been determined in detail and correlated with their functional properties. It was found that GO oxygen functional groups are reduced by the presence of TiO2 NPs in the composite materials. Photodegradation activity under UV–visible light irradiation was studied by measuring the concentration changes in time of organic methylene blue (MB) dye in aqueous solution and by measuring the chemical oxygen demand (COD) of domestic wastewater. The obtained results revealed that the photocatalytic properties of the spin coated composites can be controlled through the graphene oxide concentration. The effect of the spontaneous reduction of GO on the photocatalytic activity of the TiO2-GO composites is discussed in detail.
Phase no. 20
Responsible: Dr. F. SIMA
Title: "Acoperiri subtiri de materiale pe baza de carbon obtinute prin tehnici de depunere cu laser pulsat pentru aplicatii in stocarea de energie sau eliberarea controlata de substante active biomedical"
Abstract: In this phase we report on a fast synthesis method of porous carbon films on solid substrates. Thin carbon micro-structured films tailored by processing conditions were synthesized for the first time by Matrix-Assisted Pulsed Laser Evaporation followed by thermal treatment. The procedure consists of pulsed laser irradiation of a cryogenic target composed of phloroglucinol/glyoxylic acid organic precursors dissolved in different mixtures of solvents. An excimer UV KrF* pulsed laser was employed inside a vacuum chamber for material expulsion from the target and immobilization on a solid facing collector. By modifying laser energy or target solvents, thin polymeric coatings of hundreds of nanometers with various cross-linking degrees were obtained at room temperature. No drying or thermo-polymerization step is required even for high boiling point solvents. After thermal annealing treatment, mesoporous carbon films exhibiting diverse nano-morphologies were then directly obtained onto various collectors.
Dissemination: E. Axente, M. Sopronyi, Camé.Matei. Ghimbeu, C. Nita, A. Airoudj, G. Schrodj, F. Sima, Matrix-Assisted Pulsed Laser Evaporation: A novel approach to design mesoporous carbon films, Carbon (2017), doi: 10.1016/j.carbon.2017.06.098.
Phase no. 21
Responsible: Dr. N. PAVEL
Title: "Hybrid laser devices realized by the direct writing with fs-laser pulses"
Abstract: The objective of this work was to demonstrate multifunctional / hybrid lasers of waveguide type, operating in Q-switch mode. The writing of the waveguides was done with a Clark CPA-2101 laser system (emission at 775 nm, duration of 200 fs, frequency of 2.0 kHz) in Nd:YAG/Cr4+ composite media of crystalline type. The focusing conditions of the laser beam (fs) have been determined so as to obtain tubular waveguides of various diameters. Laser emission was obtained using the pump with a fiber-coupled diode laser. Laser pulses at 1.06 μm with energy Ep= 15.7 μJ and duration tp= 3.9 ns at the repetition rate fp= 71.9 kHz were obtained from an waveguide of 150-μm diameter that was inscribed in a Nd:YAG/Cr4+ composite medium that was composed of a 7-mm long, 1.0-at.% Nd: YAG and a Cr4+: YAG saturable absorber with initial transmission T0= 0.70. The average output power was Pave = 1.13 W.
Dissemination: G. Croitoru (Salamu), F. Jipa, and N. Pavel, “Passive Q-switch laser operation of circular, buried depressed-cladding waveguides realized by direct fs-laser beam writing in Nd:YAG/Cr4+:YAG composite media,” Opt. Mat. Express 7(7), 2496-2504 (2017).