- Magurele, Ilfov, Romania
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More than 40 years’ experience in the field of laser-material processing (ceramics, polymers, biomaterials, metals): ... moreMore than 40 years’ experience in the field of laser-material processing (ceramics, polymers, biomaterials, metals): thin film growth, PLD, MAPLE, thin film patterning and transfer LIFT, production of nanomaterials and nanoparticles, material characterization by AFM, XPS, SIMS, XRD. Editor Applied Surface Science (since 2014). edit
We measured the anelastic, dielectric and structural properties of the metal-free molecular perovskite (ABX$_{3}$) (MDABCO)(NH$_{4}$)I$_{3}$, which has already been demonstrated to become ferroelectric below $T_{\text{C}}=$ 448~K. Both... more
We measured the anelastic, dielectric and structural properties of the metal-free molecular perovskite (ABX$_{3}$) (MDABCO)(NH$_{4}$)I$_{3}$, which has already been demonstrated to become ferroelectric below $T_{\text{C}}=$ 448~K. Both the dielectric permittivity measured in air on discs pressed from powder and the complex Young's modulus measured on resonating bars in vacuum show that the material starts deteriorating with loss of mass just above $T_{\text{C}}$, introducing defects and markedly lowering $T_{\text{C}}$. The elastic modulus softens of 50\% when heating through the initial $T_{\mathrm{C}}$, contrary to usual ferroelectrics, which are stiffer in the paraelectric phase. This suggests improper ferroelectricity, where the primary order parameter of the transition is not the electric polarization, but the orientational order of the MDABCO molecules. The degraded material presents thermally activated relaxation peaks in the elastic energy loss, whose intensities increas...
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Abstract Quasi-amorphous titanium oxynitride (TiON) films were obtained by annealing sol–gel anatase TiO 2 films in NH 3 atmosphere at 600 °C. These films were irradiated with 50 laser pulses using the fourth harmonic (266 nm) radiation... more
Abstract Quasi-amorphous titanium oxynitride (TiON) films were obtained by annealing sol–gel anatase TiO 2 films in NH 3 atmosphere at 600 °C. These films were irradiated with 50 laser pulses using the fourth harmonic (266 nm) radiation of the Nd-YAG laser, with an average fluence of 20 mJ/cm 2 . HRTEM observations of the pulsed laser irradiated films evidenced the rutile TiO 2 nanocrystallites formation. The rutile structure was not present either in the TiON films before the laser irradiation, or in the initial sol–gel anatase TiO 2 films. During the laser irradiation, the film structure remains in the solid state phase, as it results from the temperature estimation and microscopic observations. For the rutile nanocrystals formation, the atomic diffusion length of the oxygen and titanium atoms should be in the nanometric range during the laser pulse action, which implies a diffusivity close to the values observed in the liquid phase. We consider that the rutile phase formation is a proof of the fast atomic diffusion in the solid amorphous matrix, during the laser irradiation.
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Engineering, Materials Science, Chemistry, Pulsed Laser Deposition, Thin Film, and 13 morePhysical sciences, Nitrogen, Laser Ablation, Diffraction, Sapphire, CHEMICAL SCIENCES, X ray diffraction, Stoichiometry, Thin film deposition, Elsevier, X Ray Diffraction Analysis, X Ray Photoelectron Spectroscopy, and Parametric Study
This paper outlines an analysis correlating new experimental data and accounting for the characteristics of aluminium heating in vacuum, up to the production of surface plasma and further, under microsecond pulsed CO2 laser radiation in... more
This paper outlines an analysis correlating new experimental data and accounting for the characteristics of aluminium heating in vacuum, up to the production of surface plasma and further, under microsecond pulsed CO2 laser radiation in the intensity range 107-1010 W cm-2.
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New data are reported concerning the plasma initiation in front of metallic and dielectric surfaces under the action of pulsed CO2 laser radiation.
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Dielectric relaxation measurements on Pb1–xLax(Zr0.65Ti0.35)1–x/4O3 with x = 0.09 (PLZT 9/65/35) thin films are presented. These films have been grown by pulsed laser deposition (PLD) assisted by radio frequency (RF) discharge in oxygen... more
Dielectric relaxation measurements on Pb1–xLax(Zr0.65Ti0.35)1–x/4O3 with x = 0.09 (PLZT 9/65/35) thin films are presented. These films have been grown by pulsed laser deposition (PLD) assisted by radio frequency (RF) discharge in oxygen which allows to increase the plasma reactivity and to reduce the oxygen vacancies in films and at the film-bottom electrode interface.The small signal dielectric constant and loss
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Physics, Condensed Matter Physics, Materials Science, Ferroelectrics, Pulsed Laser Deposition, and 12 moreDielectric Spectroscopy, Thin Film, DIELECTRIC, Radio Frequency, Domain wall, Dielectric Relaxation, Dielectric Constant, Room Temperature, Ferroelectricity, Dielectric Permittivity, Pyrochlore, and Permittivity
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AlN thin films were grown at 200–450°C on Si substrates by laser ablation of Al targets in nitrogen-reactive atmosphere using a robust and simple experimental set-up based on a Nd–YAG laser. Infrared spectroscopy results indicate the... more
AlN thin films were grown at 200–450°C on Si substrates by laser ablation of Al targets in nitrogen-reactive atmosphere using a robust and simple experimental set-up based on a Nd–YAG laser. Infrared spectroscopy results indicate the presence of two broad peaks around 679 and 644cm−1, typical of AlN compound. Spectroellipsometric spectra were recorded in the range 400–700nm: the refractive index values were found to be close to those previously reported (less than 9% variation). The cross-plane thermal conductivity of an AlN film was measured in the 80–380K temperature range by the 3ω method. The values are strongly reduced compared to those of the bulk and the temperature dependence behaviour is glass-like.
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. BaTiO3–polymer composite layers have been produced by the spin-on technique (thickness 3–10 μm). The dielectric permittivity of the layers at room temperature can be tuned from 2.8 to approximately 33 by varying the ceramic filling... more
. BaTiO3–polymer composite layers have been produced by the spin-on technique (thickness 3–10 μm). The dielectric permittivity of the layers at room temperature can be tuned from 2.8 to approximately 33 by varying the ceramic filling from 0 to 60% by volume. The dielectric properties of the films are almost insensitive to temperature variations in the range 20–180 °C. Free-standing composite layers
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We have performed optical and structural characterization of Yttria Stabilized Zirconia (YSZ) thin films prepared by pulsed laser deposition (PLD) on Si (100) and Pt/Si (100) substrates from the ablation of a 8YSZ target by ArF excimer... more
We have performed optical and structural characterization of Yttria Stabilized Zirconia (YSZ) thin films prepared by pulsed laser deposition (PLD) on Si (100) and Pt/Si (100) substrates from the ablation of a 8YSZ target by ArF excimer laser. X-ray Diffraction (XRD) analysis stated orthorhombic films with [111] preferential orientation for Pt/ Si substrate and cubic phase for Si (100) substrate. Secondary Ion Mass Spectrometry (SIMS) investigation shows a stoichiometric transfer of target composition to the substrates. By using Atomic Force Microscopy (AFM) and Variable Angle Spectroscopic Ellipsometry (VASE) we have determined the thickness, roughness, and refractive indices of thin films. Ellipsometric data were obtained with the Cauchy model in the spectral range 400-1000 nm, at three angle of incidence: 60, 65, and 70. It was obtained high-k dense YSZ thin films deposited on Si (100) with applications for electrolyte of ionic devices, like oxygen sensors.
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Page 1. 208 Research Article Received: 7 August 2009 Revised: 27 December 2009 Accepted: 29 January 2010 Published online in Wiley Interscience: 28 March 2010 (www.interscience.com) DOI 10.1002/xrs.1251 Proton µ-PIXE mapping, AFM imaging... more
Page 1. 208 Research Article Received: 7 August 2009 Revised: 27 December 2009 Accepted: 29 January 2010 Published online in Wiley Interscience: 28 March 2010 (www.interscience.com) DOI 10.1002/xrs.1251 Proton µ-PIXE mapping, AFM imaging and size ...
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Due to its physical and chemical properties, the n-type tungsten oxide (WO3) semiconductor is a suitable photoanode for water decomposition reaction. The responses of the photoelectrochemical PEC water-splitting properties as an effect of... more
Due to its physical and chemical properties, the n-type tungsten oxide (WO3) semiconductor is a suitable photoanode for water decomposition reaction. The responses of the photoelectrochemical PEC water-splitting properties as an effect of structural and optical changes of WO3 thin films, as well as the nature of electrolyte solutions, were studied in this work. The WO3 thins films have been obtained by pulsed laser deposition (PLD) on silicon (Si(001)) covered with platinum substrates using three different laser wavelengths. As the XRD (X-ray diffraction) and XTEM (cross-section transmission electron microscopy) analysis shows, the formation of highly crystalline monocline WO3 phase is formed for the film deposited at 1064 nm wavelength and poor crystalline phases with a large ordering anisotropy, characteristic of 2D structures for the films deposited at 355 nm and 193 nm wavelengths, respectively. The photogenerated current densities Jph depend on the laser wavelength, in both alk...
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This work is focused on the application of a laser-based technique, i.e., matrix-assisted pulsed laser evaporation (MAPLE) for the development of electrochemical sensors aimed at the detection of nitrites in water. Commercial carbon-based... more
This work is focused on the application of a laser-based technique, i.e., matrix-assisted pulsed laser evaporation (MAPLE) for the development of electrochemical sensors aimed at the detection of nitrites in water. Commercial carbon-based screen-printed electrodes were modified by MAPLE via the application of a newly developed composite coating with different concentrations of carbon nanotubes (CNTs), chitosan, and iron (II) phthalocyanine (C32H16FeN8). The performance of the newly fabricated composite coatings was evaluated both by investigating the morphology and surface chemistry of the coating, and by determining the electro-catalytic oxidation properties of nitrite with bare and modified commercial carbon-based screen-printed electrode. It was found that the combined effect of CNTs with chitosan and C32H16FeN8 significantly improves the electrochemical response towards the oxidation of nitrite. In addition, the MAPLE modified screen-printed electrodes have a limit of detection ...
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The production of micron-scale architectures is a major demand in several new fields in the biomedical and sensing area. In particular, engineering different materials can produce cell templates, allowing the analyses of cell adhesion and... more
The production of micron-scale architectures is a major demand in several new fields in the biomedical and sensing area. In particular, engineering different materials can produce cell templates, allowing the analyses of cell adhesion and growth, cell-cell interactions, or cell clustering. In addition, the capability to spatially control the deposition of soft materials i.e. polymers onto different types of substrates is important for the development of sensors and biosensors. In this work, the application of laser methods i.e. laser direct-writing (LDW), matrix-assisted pulsed laser evaporation (MAPLE), and laser induced forward transfer (LIFT) for obtaining controlled sized designs or thin films from a variety of soft materials is shown. Organically modified silicates (ORMOSILS) have been investigated in order to obtain polymeric structures designed by LDW that would be further used as scaffolds for tissue engineering. Collagen has been deposited by MAPLE as a thin layer, proving ...
A series of coatings from poly(ethylene-co-vinyl acetate) (EVA) were obtained using the matrix-assisted pulsed laser evaporation (MAPLE) technique. By changing the process parameters, i.e., laser fluence and EVA co-polymer concentration... more
A series of coatings from poly(ethylene-co-vinyl acetate) (EVA) were obtained using the matrix-assisted pulsed laser evaporation (MAPLE) technique. By changing the process parameters, i.e., laser fluence and EVA co-polymer concentration in the target, coatings with various morphologies and topographies were produced. The evaluation of the film structure was based on an analysis of optical and atomic force microscopy and profilometry measurements. A detailed chemical structure investigation, conducted based on Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra, revealed that although the general structure was preserved, some alterations of ethylene (Et) and vinyl acetate (VAc) blocks took place. The most noticeable change was in the ester group that was transformed into ketone and carboxyl groups; nevertheless, some changes in the aliphatic main chain were also present. The chemical structure changes in EVA coatings took place regardless of the proce...
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A transition from the monoclinic to ferroelectric orthorhombic phase, takes place within a region of few atomic layers of single HfO2 crystals. Atomic calculations show high stability of the ferroelectric orthorhombic phase.
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ABSTRACT Layered double hydroxides (LDHs) thin films with Mg-Al were deposited using pulsed laser deposition (PLD) technique. We studied the ability of our films to detect copper ions in aqueous solutions. Copper is known to be a common... more
ABSTRACT Layered double hydroxides (LDHs) thin films with Mg-Al were deposited using pulsed laser deposition (PLD) technique. We studied the ability of our films to detect copper ions in aqueous solutions. Copper is known to be a common pollutant in water, originating from urban and industrial waste. Clay minerals, including layered double hydroxides (LDHs), can reduce the toxicity of such wastes by adsorbing copper. We report on the uptake of copper ions from aqueous solution on LDH thin films obtained via PLD.
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Lead based ferroelectric thin films have been grown by pulsed laser deposition (PLD) on Si, MgO and Sapphire substrates starting from sintered targets of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) and (Pb1−xLax)(Zr0.65Ti0.33)O3 (PLZT) with variable... more
Lead based ferroelectric thin films have been grown by pulsed laser deposition (PLD) on Si, MgO and Sapphire substrates starting from sintered targets of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) and (Pb1−xLax)(Zr0.65Ti0.33)O3 (PLZT) with variable PT and La contents, respectively. A parametric study has been performed to investigate the influence of the laser wavelength (266, 355, 532 and 1064 nm), laser fluence (2–25 J/cm2), oxygen pressure (0.2–0.8 mbar), substrate temperature (400–650 °C) on the composition and crystallinity, and on dielectric, ferroelectric and piezoelectric properties. Dielectric measurements were done over a wide frequency and temperature range. The dielectric permittivity and loss were investigated for films obtained with different deposition parameters and diffuse-like features were identified in small-grain size microstructured films. The polarization-electric field dependence has been measured at different frequency and temperature conditions. Piezoelectric local probing has been performed and the dependence of longitudinal piezoelectric coefficient on microstructure and texture was obtained.
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Low cost a-SiC:H films are easily available on different substrates by Plasma Enhanced CVD. The aim of this work is the transformation of these films towards materials with applications in microelectronics (polysilicon, silicon carbide,... more
Low cost a-SiC:H films are easily available on different substrates by Plasma Enhanced CVD. The aim of this work is the transformation of these films towards materials with applications in microelectronics (polysilicon, silicon carbide, nitride, oxinitride). Laser, plasma irradiation and thermal treatments in controlled atmosphere are possible candidates to modify the chemical composition and/or the structure of the a-SiC:H films.
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Lead magnesium niobate (Pb(Mg1/3Nb2/3)O3 or PMN) thin films have been deposited on different substrates by pulsed laser deposition. Film composition was studied by secondary ion mass spectroscopy and their crystallinity by X-ray... more
Lead magnesium niobate (Pb(Mg1/3Nb2/3)O3 or PMN) thin films have been deposited on different substrates by pulsed laser deposition. Film composition was studied by secondary ion mass spectroscopy and their crystallinity by X-ray diffraction techniques. Small-signal dielectric constant and loss factor of the films have been measured as a function of temperature and frequency on structures with 3mm diameter evaporated Au
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We review our significant results concerning pulsed laser deposition (PLD) of some ferroelectric compounds: (i) lead magnesium niobate Pb(Mg1/3Nb2/3)O3 (PMN); (ii) lead magnesium niobate–lead titanate Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT),... more
We review our significant results concerning pulsed laser deposition (PLD) of some ferroelectric compounds: (i) lead magnesium niobate Pb(Mg1/3Nb2/3)O3 (PMN); (ii) lead magnesium niobate–lead titanate Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT), with variable PT contents; (iii) La-doped lead zirconate titanate (Pb1−xLax)(Zr0.65Ti0.33)O3 (PLZT); and (iv) Nb-doped lead zirconate titanate Pb0.988(Zr0.52Ti0.48)0.976Nb0.024O3 (PNZT). A parametric study has been performed in order to evidence the influence of the
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Smooth a-axis oriented ZnO thin films are grown on (001) MgO substrates by pulsed laser deposition assisted by a very directional radio frequency oxygen plasma. The structure of the film is examined by X-ray diffraction, electron... more
Smooth a-axis oriented ZnO thin films are grown on (001) MgO substrates by pulsed laser deposition assisted by a very directional radio frequency oxygen plasma. The structure of the film is examined by X-ray diffraction, electron diffraction and high resolution electron microscopy. The film grows with vertical columns and is highly textured. Two preferential orientation relations between the ZnO film
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In this study we describe a simple method to fabricate microarrays of polystyrene microbeads (PS-μbeads) on Thermanox coverslip surfaces using laser induced forward transfer (LIFT). A triazene polymer layer which acts as a dynamic release... more
In this study we describe a simple method to fabricate microarrays of polystyrene microbeads (PS-μbeads) on Thermanox coverslip surfaces using laser induced forward transfer (LIFT). A triazene polymer layer which acts as a dynamic release layer and propels the closely packed microspheres on the receiving substrate was used for this approach. The deposited features were characterized by optical microscopy, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. Ultrasonication was used to test the adherence of the transferred beads. In addition, the laser ejection of the PS-μbead pixels was investigated by time resolved shadowgraphy. It was found that stable PS-μbeads micropatterns without any specific immobilization process could be realized by LIFT. These results highlight the increasing role of LIFT in the development of biomaterials, drug delivery, and tissue engineering.
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Engineering, Physics, Materials Science, Laser, Applied Physics, and 15 moreRaman Spectroscopy, Scanning Electron Microscopy, Drug delivery, Nanotechnology, Atomic Force Microscopy, Microfabrication, Mathematical Sciences, Applied, Optical microscopy, Physical sciences, Time Resolved, Polystyrene, Scanning Electron Microscope, Materials Processing, and Raman Spectra
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In this work, antitumor compounds, lactoferrin [recombinant iron-free (Apo-rLf)], cisplatin (Cis) or their combination were embedded within a biodegradable polycaprolactone (PCL) polymer thin film, by a modified approach of a laser-based... more
In this work, antitumor compounds, lactoferrin [recombinant iron-free (Apo-rLf)], cisplatin (Cis) or their combination were embedded within a biodegradable polycaprolactone (PCL) polymer thin film, by a modified approach of a laser-based technique, matrix-assisted pulsed laser evaporation (MAPLE). The structural and morphological properties of the deposited hybrid films were analyzed by Fourier-transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). The in vitro effect on the cells' morphology and proliferation of murine melanoma B16-F10 cells was investigated and correlated with the films' surface chemistry and topography. Biological assays revealed decreased viability and proliferation, lower adherence, and morphological modifications in the case of melanoma cells cultured on both Apo-rLf and Cis thin films. The antitumor effect was enhanced by deposition of Apo-rLf with Cis within the same film. The unique capability of the new approach, based on MAPLE, to embed antitumor active factors within a biodegradable matrix for obtaining novel biodegradable hybrid platform with increased antitumor efficiency has been demonstrated.
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The aim of this work was to find the suitable high-k dielectric compound to be used as gate dielectric in MOS devices. Thin films of zirconia (ZrO2), zirconium silicate (ZrSixOy), hafnia (HfO2) and hafnium silicate (HfSixOy) with... more
The aim of this work was to find the suitable high-k dielectric compound to be used as gate dielectric in MOS devices. Thin films of zirconia (ZrO2), zirconium silicate (ZrSixOy), hafnia (HfO2) and hafnium silicate (HfSixOy) with thickness in the nanometer range have been obtained by pulsed laser deposition (PLD), assisted or not by radio-frequency discharge.For thin films of ZrO2
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Materials Science, Scanning Electron Microscopy, Atomic Force Microscopy, Multidisciplinary, Surface Roughness, and 11 moreOptoelectronics, Pulsed Laser Deposition, Thin Film, DIELECTRIC, Leakage Current, Radio Frequency, Laser Ablation, Hafnium, X ray diffraction, Scanning Electron Microscope, and Thin film deposition
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Materials Science, Metallurgy, Scanning Electron Microscopy, Cytotoxicity, Atomic Force Microscopy, and 15 moreMultidisciplinary, Cell Culture, Saccharomyces cerevisiae, Pulsed Laser Deposition, Escherichia coli, Thin Film, Medical Device, Nickel, Alloy, Microorganism, Scanning Electron Microscope, Surface Properties, Nickel Titanium, Chemical Composition, and Film Thickness
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Peptide-based arrays and patterns have provided a powerful tool in the study of protein recognition and function. A variety of applications have been identified, including the interactions between peptides–enzymes, peptides–proteins,... more
Peptide-based arrays and patterns have provided a powerful tool in the study of protein recognition and function. A variety of applications have been identified, including the interactions between peptides–enzymes, peptides–proteins, peptides–DNA, peptides–small molecules and peptides–cells. One of the main and most critical unresolved issues is the generation of high-density arrays which maintain the biological function of the peptides. In this study, we employ nanosecond laser-induced forward transfer for the generation of ...