Stage 2 - P2 2017
The project implementation schedule
Phase no. 22
Responsible: Dr. A Groza
Title: "Analyzes of nanometric films of bio interest through optical and mass spectrometry"
Abstract: In this report are presented the data obtained as result of generation of thin layers of biological interest by magnetron sputtering discharges. The physico-chemical properties of these layers have been analysed by different spectral methods like: infrared spectroscopy and glow discharge optical emission spectroscopy. By FTIR spectroscopy has been identified the absorbtion molecular bands specific to the target material. It results that by magnetron deposition technique the chemical structure of the target material is preserved in the deposited thin layer. The distribution of the chemical elements in the layer function of the layer depth was determined by glow discharge optical emission spectroscopy. A diffusion of the chemical elements into the substrate has also been identified. By mass spectrometry was acquired and analysed the molecular fragments generated in the magnetron discharge during the deposition process.
Phase no. 23
Responsible: Dr. I. Jepu
Title: "Achievement of carbon content tribological structures obtained by reactive magnetron/TVA methods – comparative study"
Abstract: In this project two types of structures, namely SiC using the TVA method and SiCN using the r-HiPIMS technique were successfully obtained. The aim was a comparative study from the morphological and structural point of view the two layers in order to assess their tribological properties. SEM imaging highlighted a reduced surface morphology and the lack of any major imperfections on both studied samples. Moreover, the cross-section SEM imaging revealed a compact growth of each individual layer, coted on one hand using TVA technology, or the r-HiPIMS technique which in turn reflects ion bombardment significance of the two types of plasma used. TDS analysis have confirmed the presence of N in the SiCN structure. Nitrogen desorption was found to start at 2000C and increases until the highest baking temperature was reached. An important aspect which is worth mentioning consist in the nitrogen TDS spectrum synchronization with the molecular O2 spectrum, which implies either that N acts as a desorption barrier either that both elements are chemically bounded. RBS analysis showed the presence of nitrogen in the whole volume of the obtained layer for the SiCN structures. Both SiC and SiCN films were found to have an increased level of oxygen contamination ~10at%. For the samples obtained by HiPIMS it was noticed a nearly uniform distribution of Si and C in the SiCN structure. Tribological measurements showed that the friction coefficient for both structures varied from 0.15 to 0.25. SEM imaging on the wear traces following tribological assessment highlighted an exfoliation for both of the studied layers. Despite this factor, in both cases the studied surfaces present some beneficial tribological properties due to the formation of carbide-carbide contact which is ideal for dry lubrication functionality.
Phase no. 24
Responsible: Dr. M. Nistor
Title: "Study of transparent electronic devices obtained by plasma techniques from advanced oxide materials"
Abstract: In this phase we pursued the fabrication of demonstrative transparent electronic devices obtained by plasma techniques from advanced oxide materials, on substrates adapted to the integration in applications. These transparent electronic devices are based on thin film transistors for which self-assembled source-channel-drain structures were obtained in a single deposition process, using the pulsed electron beam ablation method with contactless shadow-mask. The electrical and optical performances of the transparent electronic devices have been investigated, highlighting the permanent electrical switching effect in the case of long channel.
Phase no. 25
Responsible: Dr. F. Dumitrache
Title: "Sinteza prin piroliza laser de nanoparticule pe baza de Sn, Zn si/sau Ti"
Abstract: Zinc-doped tin oxide nanoparticles, were synthesized by the laser pyrolysis using a reactive mixture containing vapors of tetramethyl-Sn and diethyl-Zn carried by Ar, SF6 or C2H4 as sensitizer. Synthetic air or a mixture of oxygen and argon was used as an oxidant. TEM and XRD analysis of the synthesized nanopowders demonstrate an improved crystalline structure oriented to crystalline mono-domains when the oxygen percentage increases in the reactive mixture. Zn doping degree (up to 5 at. %) can be finely tuned by controlling Zn/Sn precursors ratio with a mean particle diameter about 12 to 15 nm as EDX and TEM analyses revealed. Zinc doped tin oxide nanostructures exhibit optical transparency and electrical conductivity. Regarding the obtaining of Ti based nanoparticles this work is aimed to phase control, experimentally studied, by parameter modulation, during one step laser pyrolysis synthesis. High phase purity anatase and rutile TiO2 nanoparticles, oxygen abundant, are synthesized from TiCl4 and C2H4 gas mixtures, in the presence of air as oxygen donor, under CO2 laser radiation. The nano-titania samples are analyzed by X-ray Diffraction, EDX, TEM and Raman spectroscopy and reveal good phase stability and distinct morphology.
Phase no. 26
Responsible: Dr. E. Axente
Title: "Compositional analyses of the synthesized combinatorial libraries by calibration-free LIBS in air versus argon. Comparison with complementary techniques like RBS and EDX"
Abstract: We demonstrate that quantitative analyses of the elemental composition of nanoscaled thin films can be performed using calibration-free laser-induced breakdown spectroscopy (CF-LIBS). Therefore, SiGe films produced by combinatorial-pulsed laser deposition on sapphire of a thickness smaller than 100 nm and variable elemental composition were ablated with ultraviolet nanosecond laser pulses. The emission spectrum of the laser-produced plasma recorded with an Echelle spectrometer coupled to a gated detector was compared to the spectral radiance computed for a plasma in local thermodynamic equilibrium. Using an iterative calculation loop, the elemental composition was deduced from the best agreement between measured and computed spectra. It is shown that for ablation in argon background gas, the plasma is almost uniform and can be described by unique values of temperature and electron density. Contrarily, the plasma produced in ambient air exhibits a hot core enclosed by a colder peripheral zone, which requires a more elaborated radiation model for simulations. However, as the cold plasma periphery mostly contributes to the plasma emission spectrum via absorption, its contribution can be neglected as long as optically thin lines are used for the analyses. Finally, the analyses of the thin films via laser-induced breakdown spectroscopy were validated by comparing the deduced elemental composition to the values measured by Rutherford backscattering. It is shown that a measurement accuracy of about 5% can be obtained and that the main source of measurement errors is due to uncertainties of spectroscopic data.
Phase no. 27
Responsible: Dr. C. Ticos
Title: "Characterization of radiofrequency plasma interacting with a 15 keV electron beam"
Abstract: Phase 27/2017 is a continuation of the activities of Phase 11/2016 and consists in radiofrequency plasma characterization when interacting with a 15 keV electron beam. The floating potential and plasma potential were determined using the Langmuir probe method and an electron density of 8,5×1015/m3 while the electron temperature is 5,1 eV. The self-bias voltage was determined and it was found to decrease with increasing pressure in the interaction chamber and it increases with the rf power. The same behavior is observed at the self-bias voltage at the introduction of the electron beam into the plasma. The beam current was evaluated in the interaction chamber and maximum values of 7 mA were obtained. The beam current value is influenced by both plasma pressure and beam focusing conditions. A better understanding of the parameters characterizing plasma and the electron beam in the interaction chamber is necessary to understand the interaction between the beam and micro / nanoparticles levied in the plasma. This interaction is to be carried out within Phase No 28 of 2017.
Phase no. 28
Responsible: Dr. C. Ticos
Title: "Acceleration by electron beams of plasma levitated nano/microparticles"
Abstract: Phase 28/2017 is a continuation of the activities of Phase 27/2017 and consists in microparticle levitation in a rf plasma and subsequent acceleration by a 14 keV electron beam. Microparticles were viewed from the side and from the top using a high speed Photron CCD and they were illuminated with a laser diode having 20 mW at 635 nm during all the experiments. We used microparticles of plastic (melamine formaldehide-MF) with diameter 11 µm in experiments with side view and with diameter 6 µm in experiments with top view. The argon pressure inside the interaction chamber was 75 to 130 mTorr while the rf power applied on the electrodes was 1W. We determined the trajectories of the microparticles after different time intervals using the Particle Tracking Velocimetry (PTV) technique.
Phase no. 29
Responsible: Dr. S. Vizireanu/ Dr. D. Stoica
Title: "Study of modification of nanomaterials by plasma immersion in their liquid dispersions"
Abstract: Direct functionalization of nanomaterials in their suspension may have a great importance for in nanomaterials manipulation, because it could avoid their agglomeration and precipitation. On the other hand, the added functional groups which facilitate the dispensability control could change other properties of the nanomaterials (their electrical transport, wettability, biocompatibility and their capacity to storage electric charge, etc.). Plasma in liquid methods for suspensions treatment is very promising and recent compared to chemical methods.
The purpose of experiments in this stage was to modify the nanomaterials properties by submerged plasma treatment applied to their liquid dispersions. To this aim, we used 2 types of plasma jets (DBE and DBD) generated in different gas mixtures. These plasma jets were immersed in the suspensions of graphene, graphene oxide-GOx, reduced graphene oxide rGO and carbon nanotubes -NT.
The functionalization of nanomaterials was achieved by introducing in the argon gas sustaining the discharge reactive gases (oxygen, nitrogen, ammonia, etc.) or by adding a liquid reagent (acetonitrile) in their suspension. The changes produce by plasma treatment was investigated by SEM, FTIR, Raman, and XPS methods on the materials obtain after suspensions drying. The oxygen and nitrogen functional groups incorporation was determined for all suspensions (GOx, rGO and NT). The type of functional groups can be selected according to the discharge characteristics (first of all by the input gas, but also by the plasma source type). The investigation results guide us in identification of ways for modification of the nanostructures properties, as well as to identify the right treatment parameters that introduce some specific groups. The tested technique for suspensions treatment could be extended to other dispersions of materials (nanoparticles, nanocellulose, polymers, etc.).
Phase no. 30
Responsible: Dr. A. Marcu
Title: "Fabrication, characterization and properties control of hetero-nanowires grown by laser techniques"
Abstract: Using pulsed laser deposition (PLD) in a plasma reflection configuration for plume filtering (PLD/PR) oxide nanowires were grown through vapour-liquid-solid (VLS) technique. Using the same experimental system but changing the growing conditions, nanowires were covered with auxiliary layers from same or different materials. Thus, deposition conditions like laser energy per pulse or train pulses, number of pulses and deposition temperature were controlling growing morphology and respectively nanostructure/layer structural properties. Nanostructure characterization was performed buy scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and the results have shown the possibility of controlling the morphology and structural properties of the shell layer for various materials, and even for layers from the same material as the core structure.
Phase no. 31
Responsible: Dr. O. Toma
Title: "Upconversion mechanisms in rare-earth-doped oxide nanomaterials with low-energy phonons"
Abstract: The upconversion properties of the crystalline material Er:BaGd2ZnO5 are studied. This compound is characterized by low-energy (around 360 cm-1) phonons and is a promising host for upconversion. Nanocrystalline powders of this compound are synthesized by a citrate-EDTA method; bulk samples of the same compound were synthesized by solid-state reaction. The morphology and structure of the samples were studied by SEM and XRD; a good phase purity of the samples is found. By a Judd-Ofelt analysis, the transition probabilities of Er3+ in BaGd2ZnO5 are found, as well as the radiative lifetimes of the main energy levels involved in upconversion emission (2H211/2, 4S3/2 and 4F9/2). These new data were used to calculate the quantum efficiencies of upconversion-emitting levels (2H211/2, 4S3/2) and 4F9/2. Green and red upconversion emission in Er:Yb:BaGd2ZnO5 is observed; the main upconversion mechanisms are identified. The intensity of the upconversion emission in Er:Yb:BaGd2ZnO5 is compared to the intensity of upconversion emission in Er:Yb:CaSc2O4 and found greater.