-
[show abstract]
[hide abstract]
ABSTRACT: In this study, we present the deposition of ZnPc, Alq3, and PTCDA thin films using Matrix Assisted Pulsed Laser Evaporation
(MAPLE) technique. We also report the realisation of multilayer structures, made by the successive application of MAPLE. The
films have been characterized by spectroscopic (UV–VIS and Photoluminescence) and microscopic (SEM and AFM) methods, and the
effect of different deposition conditions such as fluence, number of pulses, and target concentration on the properties has
been analysed. This paper also presents some investigations on the electrical conduction in sandwich type structures ITO or
Si/organic layer/Au or Cu and ITO/double organic layer/Cu, emphasising the dominant effect of the height of the energetic
barriers at the inorganic/organic and organic/organic interfaces.
Applied Physics A 04/2012; 104(3):921-928. · 1.63 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The synthesis by pulsed laser deposition of ZnO thin films with a Nd:YAG laser system delivering pulses of 40ps @ 532 nm
is reported. The laser beam irradiated the target placed inside a vacuum chamber evacuated down to 1.33×10−1 Pa. The incident laser fluence was of 28 J/cm2 in a spot of 0.1mm2. The ablated material was collected onto double face polished (111) Si or quartz wafers placed parallel at a separation distance
of 7mm. The AFM, SEM, UV-Vis, FT-IR and absorption ellipsometry results indicated that we obtained pure ZnO films with a
rather uniform surface, having an average roughness of 37nm. We observed by SEM that particulates are present on ZnO film
surface or embedded into bulk. Their density and dimension were intermediary between particulates observed on similar structures
deposited with fs or ns laser pulses. We noticed that the density of the particulates is increasing while their average size
is decreasing when passing from ns tops and fs laser pulses. The average transmission in the UV-Vis spectral region was found
to be higher than 85%.
Applied Physics A 04/2012; 104(3):871-876. · 1.63 Impact Factor
-
Thin Solid Films 01/2011; 520(4):1251-1258. · 1.89 Impact Factor
-
A Stanculescu,
L Vacareanu,
M Grigoras,
M Socol, G Socol,
F Stanculescu,
N Preda,
E Matei,
I Ionita,
M Girtan,
I N Mihailescu
Applied Surface Science 01/2011; 257(12):5298-5302. · 2.10 Impact Factor
-
Journal of Optoelectronics and Advanced Materials 01/2010; 12(3):731-739. · 0.46 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The increasing interest in strontium incorporation into biomaterials for hard tissue repair is justified by the growing evidence of its beneficial effect on bone. We successfully synthesized hydroxyapatite (HA) thin films with different extents of strontium substitution for calcium (0, 1, 3 or 7 at.%) by pulsed-laser deposition. The coatings displayed a granular surface and a good degree of crystallinity, which slightly diminished as strontium content increased. Osteoblast-like MG63 cells and human osteoclasts were cultured on the thin films up to 21 days. MG63 cells grown on the strontium-doped HA coatings displayed normal morphology, good proliferation and increased values of the differentiation parameters, whereas the number of osteoclasts was negatively influenced by the presence of strontium. The positive effect of the ion on bone cells was particularly evident in the case of coatings deposited from HA at relatively high strontium contents (3-7%), where significantly increased values of alkaline phosphatase activity, osteocalcin, type I collagen and osteoprotegerin/TNF-related activation-induced cytokine receptor ratio, and considerably reduced values of osteoclast proliferation, were observed.
Acta biomaterialia 06/2008; 4(6):1885-93. · 3.98 Impact Factor
-
G. Socol,
E. Axente,
C. Ristoscu,
F. Sima,
A. Popescu,
N. Stefan,
I. N. Mihailescu,
L. Escoubas,
J. Ferreira,
S. Bakalova,
A. Szekeres
[show abstract]
[hide abstract]
ABSTRACT: We demonstrated that doping or covering with Au nanoclusters boosts gas sensing effectiveness of optical metal oxide sensors. The sensing response of pulsed laser deposited ZnO films as sensing element was tested by m-line technique for low concentration (1000 ppm) of butane in environmental N2. The optical interrogation was performed for three types of coatings: undoped ZnO, undoped ZnO structures partially covered with Au nanoclusters, or obtained from Au (0.5 wt %) doped ZnO targets. Nanocluster coating tripled the sensitivity, while doping resulted in an increase of up to 45% as compared with simple structures.
Journal of Applied Physics 10/2007; 102(8):083103-083103-6. · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Thin films of erbium-doped yttrium aluminum garnet (Er:Y3Al5O12) were grown by pulsed laser deposition (PLD) followed by high temperature annealing. Such films are very appropriate for
use in planar waveguide lasers and can be used in medical and telecommunication applications as well.
12/2005: pages 369-372;
-
[show abstract]
[hide abstract]
ABSTRACT: We are reporting new features of metal oxide coatings for gas detection applications based upon the modification of the optical
parameters in order to measure gas concentrations.
12/2005: pages 363-366;
-
[show abstract]
[hide abstract]
ABSTRACT: We report the detection of 100 ppm of butane in superatmospheric N <sub>2</sub> or air with an m -lines setup. The sensing elements are ZnO-nanostructured coatings prepared by pulsed laser deposition. The deposition technique was optimized to obtain highly transparent films of 1 cm <sup>2</sup> in area and several hundreds nanometer thick. ZnO structures preserve gas sensitivity even when deposited at room temperature. Refractive index variations down to 0.005 were detected and typical variations of about 20% were induced during ZnO film-butane contact.
Journal of Applied Physics 11/2005; · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Octacalcium phosphate (OCP) and Mn(2+)-doped carbonate hydroxyapatite (Mn-CHA) thin films were deposited on pure, highly polished and chemically etched Ti substrates with pulsed laser deposition. The coatings exhibit different composition, crystallinity and morphology that might affect their osteoconductivity. Human osteoblasts were cultured on the surfaces of OCP and Mn-CHA thin films, and the cell attachment, proliferation and differentiation were evaluated up to 21 days. The cells showed a normal morphology and a very good rate of proliferation and viability in every experimental time. Alkaline phosphatase activity was always higher than the control and Ti groups. From days 7 to 21 collagen type I production was higher in comparison with control and Ti groups. The level of transforming growth factor beta 1 (TGF-beta1) was lower at 3 and 7 days, but reached the highest values during following experimental times (14 and 21 days). Our data demonstrate that both calcium phosphate coatings favour osteoblasts proliferation, activation of their metabolism and differentiation.
Biomaterials 06/2005; 26(15):2381-9. · 7.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The structure, chemical composition, and optical properties of tungsten trioxide thin films grown by pulsed laser deposition were investigated. An ultraviolet KrF* excimer laser (λ = 248 nm, τFWHM ≅ 20 ns, ν = 2 Hz) was used for irradiation of tungsten trioxide targets in oxygen atmosphere. Our research focused on the effect of the ambient gas pressure and substrate temperature on the chemical composition, crystalline status, and optical properties of the obtained thin films. To this end, the films were studied by x-ray diffractometry Raman spectroscopy, and energy dispersive x-ray spectroscopy. Optical transmittance measurements were performed with a double beam spectrometer within the 400–1200 nm range. The films deposited at oxygen pressure values higher than 10 Pa and substrate temperatures above 300 °C consist of crystalline tungsten trioxide. Their average transmittance in the visible-infrared spectral region reaches about 85% appropriate for the envisaged applications.
Journal of Applied Physics. 04/2005; 97(9):093527-093527-4.
-
[show abstract]
[hide abstract]
ABSTRACT: Structures of hydroxyapatite (HA) as thin films, with and without buffer layers, were deposited on Commercially Pure Titanium Grade 4 (c.p. Ti gr4) substrates by Pulsed Laser Deposition. They were afterwards heat treated in water vapours. In this study, processes taking place at the hydroxyapatite/Hank's Solution interface are investigated. The experiment consists of immersing the films in Hank's Solution for 21 days, at a constant temperature of 37°C. The composition and the morphology of the films are investigated before and after the experiment. The deposited layer was neither dissolved nor destroyed due to hydroxyapatite's good chemical stability and adherence to substrate. Moreover, at the hydroxyapatite/Hank's Solution interface the formation of a uniform Ca 2 P 2 O 7 thin layer is detected, which could lead to a better bio-integrability. Also, single micro-crystals of NaCl are observed on the surface of the samples after the experiment, demonstrating the good surface conditions for cell-adhesion. No Ca 2 P 2 O 7 is synthesized in the case of the reference sample (Ti without deposition), while the NaCl (Halite) crystals were very small. Our findings confirm the better biological simulated behaviour of hydroxyapatite films, demonstrating very convincing premises for bio-integration and bio-activity.
Romanian Reports in Physics. 01/2005; 57:1003-1010.
-
[show abstract]
[hide abstract]
ABSTRACT: Mn(2+)-doped carbonated hydroxyapatite (Mn-CHA) thin films were obtained by pulsed laser deposition on Ti substrates. The results of the performed complementary diagnostic techniques, X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy investigations indicate that the films are crystalline with a Ca/P ratio of about 1.64-1.66. The optimum conditions, when nearly stoichiometric crystalline thin films were deposited, were found to be 10 Pa oxygen pressure, 400 degrees C substrate temperature, and postdeposition heat treatment in water vapors at the same substrate temperature. The films were seeded with L929 fibroblast and hFOB1.19 osteoblast cells and subjected to in vitro tests. Both fibroblast and osteoblast cells have a good adherence on the Mn-CHA film and on the Ti or polystyrene references. Proliferation and viability tests showed that osteoblast cells growth on Mn-CHA-coated Ti was enhanced as compared to uncoated pure Ti surfaces. Caspase-1 activity was not affected significantly by the material, showing that Mn-CHA does not induce apoptosis of cultured cells. These results demonstrate that Mn-CHA films on Ti should provoke a faster osteointegration of the coated implants as compared to pure Ti. (c) 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 353-358, 2004.
Journal of Biomedical Materials Research Part A 12/2004; 71(2):353-8. · 2.63 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We extended for the first time pulsed laser ablation to the deposition of octacalcium phosphate Ca8H2(PO4)6.5H2O (OCP) thin films. The depositions were performed with a pulsed UV laser source (lambda=248 nm, tau> or =20 ns) in a flux of hot water vapors. The targets were sintered from crystalline OCP powder and the laser ablation fluence was set at values of 1.5-2 J/cm2. During depositions the collectors, Si or Ti substrates, were maintained at a constant temperature within the range 20-200 degrees C. The resulting structures were submitted to heat treatment in hot water vapors for up to 6 h. The best results were obtained at a substrate temperature of 150 degrees C during both deposition and post-deposition treatment. High-resolution electron microscopy and XRD at grazing incidence indicated that the coatings obtained were made of nanocrystalline OCP. Cross-section TEM investigations showed that the coatings contained droplets stacked on Ti substrates as well as distributed across the entire thickness of the arborescence-like structure layers. The results of WST-1 assay, cell adherence, DNA replication, and caspase-1 activity confirmed the good biocompatibility of the coatings.
Biomaterials 06/2004; 25(13):2539-45. · 7.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Octa-calcium phosphate (OCP), Ca8(HPO4)2(PO4)4·5H2O, is present as transient compound in the precipitation of hydroxyapatite (HA) and biological apatites. Because of these characteristics, OCP plays a crucial role in the in-vivo mineralization of human bones and teeth. The use of OCP in developing new generations of bone prosthesis stands therefore for an innovative challenge. This paper reports studies of OCP structures grown in the form of thin films by pulsed laser deposition (PLD) with emphasis on electron microscopy investigations. OCP films were grown on etched Ti substrates, using an UV KrF* excimer laser source (λ=248 nm, τ≥20 ns). Films were deposited in low-pressure (50 Pa) water vapors environment on substrates heated at 20–180 °C. We performed annealing treatments in water vapors and ambient pressure at substrate temperatures identical to those used during deposition. Comprehensive structural and morphological investigations were carried out with different based-electron microscopy procedures. Grazing incidence X-ray diffraction (GIXRD) and white light confocal microscopy were also applied to characterize the films. Ca/P atomic ratio of films was determined by energy dispersive X-ray spectrometry, electron energy loss spectroscopy and X-ray photoelectron spectroscopy. The obtained films generally exhibit an amorphous structure, as evidenced by GIXRD. Nevertheless, cross-section transmission electron microscopy investigations provide supplementary information about the film characteristics and material crystallization in small domains. OCP nanoparticles coalesce and grow perpendicular to the substrate in a tree-like structure, comparable to a coral reef.
Thin Solid Films.
-
[show abstract]
[hide abstract]
ABSTRACT: The increasing interest in strontium incorporation into biomaterials for hard tissue repair is justified by the growing evidence of its beneficial effect on bone. We successfully synthesized hydroxyapatite (HA) thin films with different extents of strontium substitution for calcium (0, 1, 3 or 7 at.%) by pulsed-laser deposition. The coatings displayed a granular surface and a good degree of crystallinity, which slightly diminished as strontium content increased. Osteoblast-like MG63 cells and human osteoclasts were cultured on the thin films up to 21 days. MG63 cells grown on the strontium-doped HA coatings displayed normal morphology, good proliferation and increased values of the differentiation parameters, whereas the number of osteoclasts was negatively influenced by the presence of strontium. The positive effect of the ion on bone cells was particularly evident in the case of coatings deposited from HA at relatively high strontium contents (3–7%), where significantly increased values of alkaline phosphatase activity, osteocalcin, type I collagen and osteoprotegerin/TNF-related activation-induced cytokine receptor ratio, and considerably reduced values of osteoclast proliferation, were observed.
Acta Biomaterialia.
-
[show abstract]
[hide abstract]
ABSTRACT: Octacalcium phosphate (OCP) and Mn2+-doped carbonate hydroxyapatite (Mn-CHA) thin films were deposited on pure, highly polished and chemically etched Ti substrates with pulsed laser deposition. The coatings exhibit different composition, crystallinity and morphology that might affect their osteoconductivity. Human osteoblasts were cultured on the surfaces of OCP and Mn-CHA thin films, and the cell attachment, proliferation and differentiation were evaluated up to 21 days. The cells showed a normal morphology and a very good rate of proliferation and viability in every experimental time. Alkaline phosphatase activity was always higher than the control and Ti groups. From days 7 to 21 collagen type I production was higher in comparison with control and Ti groups. The level of transforming growth factor beta 1 (TGF-β1) was lower at 3 and 7 days, but reached the highest values during following experimental times (14 and 21 days). Our data demonstrate that both calcium phosphate coatings favour osteoblasts proliferation, activation of their metabolism and differentiation.
Biomaterials.
-
[show abstract]
[hide abstract]
ABSTRACT: AlN thin films with thickness in nanometer range were prepared by pulsed laser deposition techniques and by reactive sputtering techniques. Investigations by XRD, SEM, AFM, and piezoelectric measurement were performed on the obtained AlN thin films. A comparison between some of the properties of the two types of films is presented.
Semiconductor Conference, 2003. CAS 2003. International;
-
[show abstract]
[hide abstract]
ABSTRACT: AlN thin films were prepared on p-type Si(1 0 0) substrates heated at 800 °C by pulsed laser ablation of AlN targets using an UV KrF* (λ = 248 nm, τFWHM ≤ 10 ns) excimer laser. We report herewith new results in depositing AlN films from AlN targets and their characterization by X-ray diffraction (XRD), along with Fourier transform infrared (FTIR) investigations in reflection and spectroscopic ellipsometry data. The X-ray investigations confirm the formation of polycrystalline AlN films. We observed the complete absence of the Al line in the XRD spectra. The gradual decomposition of the AlN target in the zones beneath and around the crater, induced by nanosecond multipulse laser irradiation, was compensated by a low-pressure N2 flux (0.1–10 Pa) during deposition. The reflection IR spectra display features characteristic to LO phonons in AlN. Ellipsometric measurements evidenced a refractive index of 2.00 and an extinction coefficient of 0.0001 for AlN films with a thickness of about 100 nm.
Applied Surface Science 248:411-415. · 2.10 Impact Factor
