[show abstract][hide abstract] ABSTRACT: The paper investigates the dependence of the optical properties on cation concentration of amorphous-like indium gallium zinc oxide thin films (In x − w Ga w Zn1−xO1+0.5x−δ) with various (In + Ga)/(In + Ga + Zn) and Ga/(In + Ga) ratios obtained by pulsed laser deposition. X-ray reflectivity and spectroscopic ellipsometry thickness results were in good agreement. The proportionality between density and the refractive index in the transparency range is evidenced. The extracted physical parameters are clearly influenced by the variation of cation concentration.
[show abstract][hide abstract] ABSTRACT: ZrC/TiN and ZrC/ZrN multilayers thinner than 350 nm were grown on (100) Si substrates at a temperature of 300 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser (λ=248 nm, pulse duration τ=25 ns, 8.0 J/cm2 fluence and 40 Hz repetition rate). Cross-sectional transmission electron microscopy, Auger electron spectroscopy depth profiling and simulations of X-ray reflectivity curves indicated that there was intermixing between the deposited layers at the interfaces as well as between the first layer and the substrate. Nanoindentation investigations found hardness values between 35 and 38 GPa for the deposited multilayers. Linear unidirectional sliding wear tests were conducted using a ball-on-plate tribometer under 1 N normal force. Wear tracks were produced in a Hysitron nanoindenter with 1 μm radius diamond tip under a 500 μN load. High-resolution cross-sectional transmission electron microscopy studies of the wear tracks showed that the multilayers withstood these tests without significant damage. The results could be explained by the use of a high laser fluence during deposition that resulted in very dense and strongly adherent nanocrystalline layers.
Applied Physics A 08/2013; 110(3). · 1.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: We report on thin film deposition by matrix assisted pulsed laser evaporation (MAPLE) of two polymer–drug composite thin film systems. A pulsed KrF* excimer laser source (λ = 248 nm, τ = 25 ns, ν = 10 Hz) was used to deposit composite thin films of poly(d,l-lactide) (PDLLA) containing several gentamicin concentrations. FTIR spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical structures similar to those of drop cast materials. Scanning electron microscopy data indicated that MAPLE may be used to fabricate thin films of good morphological quality. The activity of PDLLA–gentamicin composite thin films against Staphylococcus aureus bacteria was demonstrated using drop testing. The influence of drug concentration on microbial viability was also assessed. Our studies indicate that polymer–drug composite thin films prepared by MAPLE may be used to impart antimicrobial activity to implants, medical devices, and other contact surfaces.
[show abstract][hide abstract] ABSTRACT: We report on the fabrication of magnetite/salicylic acid/silica shell/antibiotics (Fe(3)O(4)/SA/SiO(2)/ATB) thin films by matrix-assisted pulsed laser evaporation (MAPLE) to inert substrates. Fe(3)O(4)-based powder have been synthesized and investigated by XRD and TEM. All thin films were studied by FTIR, SEM and in vitro biological assays using Staphylococcus aureus and Pseudomonas aeruginosa reference strains, as well as eukaryotic HEp-2 cells. The influence of the obtained nanosystems on the microbial biofilm development as well as their biocompatibility has been assessed. For optimum deposition conditions, we obtained uniform adherent films with the composition identical with the raw materials. Fe(3)O(4)/SA/SiO(2)/ATB thin films had an inhibitory activity on the ability of microbial strains to initiate and develop mature biofilms, in a strain- and antibiotic-dependent manner. These magnetite silica thin films are promising candidates for the development of novel materials designed for the inhibition of medical biofilms formed by different pathogenic agents on common substrates, frequently implicated in the etiology of chronic and hard to treat infections.
[show abstract][hide abstract] ABSTRACT: A sandwich structure of four double layers of Ag (5 nm)/As 2 S 3 (82.7 nm) has been prepared by Pulsed Laser Deposition (PLD) method. The effect of broadband light on the multilayer structure has been investigated. The X-ray reflectivity (XRR) patterns after different irradiation times have been measured. Although the fully intermixing of Ag and As 2 S 3 layers should be expected during irradiation with visible light, however even after 5 h of irradiation the intermixing is not completed. The characteristic features of XRR diagrams for long irradiation times have been interpreted by scattering of X-ray radiation on clusters of Ag or Ag–As 2 S 3 .
Journal of Non-Crystalline Solids 01/2013; · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this work the synthesis of vanadium nitride ultra-thin films by means of pulsed laser deposition technique is reported. The solid target used for laser ablation was prepared from vanadium nitride powder synthesised by sol–gel of V2O5 followed by temperature programmed reduction with ammonia. The films deposition was performed at room temperature and 500 °C on glass or Si substrates and the films were characterised by different techniques, i.e., Scanning and Transmission Electron Microscopy, X-Ray Diffraction, Atomic Force Microscopy and X-ray Photoelectron Spectroscopy. As a function of the deposition conditions, the films present different thicknesses, reveal a homogenous dense to slightly porous morphology and are highly crystalline. As determined by X-ray Photoelectron Spectroscopy analyses the VN films are nitrogen deficient due to the formation of an oxide layer on their surface. The possibility of depositing crystalline VN ultra-thin films at room temperature using a VN target is of great importance for several possible applications where low temperature substrates are employed.
Surface and Coatings Technology 10/2012; · 1.94 Impact Factor
[show abstract][hide abstract] ABSTRACT: Laser induced periodical surface structures (LIPSS) are obtained on extended area of zinc oxide thin films by femtosecond laser pulses. The ZnO films deposited by pulsed laser deposition (PLD) technique were irradiated by femtosecond laser beam with 200 fs pulse duration, at 775 nm central wavelength and 2 kHz repetition rate. The irradiation conditions such as laser fluence and scanning speed were varied for each sample. The morphology and the crystalline structure of the LIPSS on ZnO films were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) for different substrates such as fused silica, crystalline SiO2, MgO, Al2O3, or Si wafers with different crystal orientation. The LIPSS appear on all ZnO films, deposited on crystalline substrates, as well as on amorphous substrates. However, more irregular nanostructures, such as bifurcations or nanodroplets were observed on ZnO with MgO, and r-Al2O3 substrates. The ZnO LIPSS are polycrystalline when fused silica, and SiO2 (0 0 0 1) substrates are used.
[show abstract][hide abstract] ABSTRACT: Single molecule magnets are of great interest due to a multitude of potential applications for some of which thin films are required. Traditional physical vapor deposition techniques are not suitable for the deposition of these fragile materials with low decomposition temperatures. Matrix Assisted Pulsed Laser Evaporation technique has been employed for the growth of thin films of the single molecule magnet Mn12(Propionate) on Si and glass substrates. In this paper we report on the appropriate growth conditions and also the morphology, chemical composition and magnetic behavior of the films. Continuous Mn12(Propionate) films with properties similar to bulk materials have been obtained.
[show abstract][hide abstract] ABSTRACT: Indium zinc oxide (IZO) thin films were obtained using pulsed laser deposition. The samples were prepared by ablation of targets with In concentrations, In/(In + Zn), of 80 at.%, at low substrate temperatures under reactive atmosphere. IZO films were used as transparent electrodes in polymer-based – poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 1:1 blend – photovoltaic cells. The action spectra measurements revealed that IZO-based photovoltaic structures have performances comparable with those using indium–tin–oxide as transparent electrode.
Thin Solid Films 09/2012; 520(22):6803–6806. · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: Two step laser processing has been used for the formation of nano-lenslets transmitting in red/infrared region of the optical spectrum on the surface of arsenic sulphide glass films. In the first step the films were obtained by pulsed laser deposition (248 nm), while in the second step the lenslets were created by low power femtosecond (800 nm) laser irradiation. Photoexpansion of the material along with simultaneous migration of chalcogen atoms in the irradiated area was the main phenomena involved in the generation of these structures. The maximum photoexpansion observed was 5.1%. At higher laser power, material ablation was evidenced.
Journal of Applied Physics 08/2012; 112:033105. · 2.21 Impact Factor
[show abstract][hide abstract] ABSTRACT: Good understanding of how properties can be tuned by changing the size of material is a basic prerequisite for production of new materials with designed superior properties. Systems with charge density wave (COW) as a type of coupled electronic-lattice instability (usually found in low dimensional materials) are especially interesting due to their exceptional properties such as giant dielectric constant, nonlinear transport, memory effects, unusual electro-mechanical and thermoelectric properties, all of conceptual importance in various thin film applications. On the other hand, COW films open the door for studying of meso- and micro-scale aspects of COW physics caused by finite size effects. Our previously produced thin granular films of CDW prototype system K0.3MoO3 (blue bronze) did not show evidence of COW condensation in the electrical transport measurements, and femtosecond time-resolved spectroscopy was established as the most appropriate method for characterization of CDW ground state in those nanocrystalline grains. However, the new films prepared by improved pulsed laser deposition (PLO) set-up in optimal conditions and characterized by various standard methods such as GI-XRD, electric transport, TOF-ERDA, AFM and UV-vis spectroscopy exhibit better properties. Electrical resistance decreased by three orders of magnitude and an indication of the Peierls transition is found in films with the best texture, which means that we have achieved the first requirement for testing of other interesting COW properties related to the size effect (and possible applications of these blue bronze films).
[show abstract][hide abstract] ABSTRACT: Thin granular films of charge density wave (CDW) system K0.3MoO3 were prepared by pulsed laser deposition and investigated by various standard characterization methods such as GI-XRD, electric transport, TOF-ERDA, AFM and UV–visible spectroscopy. While all these methods indicate that the thin films consist of nanometer grains of K0.3MoO3, it is only the non-destructive femtosecond time-resolved spectroscopy (fsTRS) that demonstrates the charge density wave nature of the ground state and therefore proves directly the presence of K0.3MoO3. Furthermore, the comparison of the fsTRS data obtained in thin films and in single crystals shows the reduction of the charge density wave transition temperature and of the photoinduced signal strength in granular thin films with respect to single crystals, which is attributed to the granularity and crystal growth morphology. Our results establish fsTRS technique as the essential tool for the detection and characterization of complex ground states in nano-sized systems.
Physica B Condensed Matter 06/2012; 407(11):1889–1893. · 1.33 Impact Factor
[show abstract][hide abstract] ABSTRACT: Pulsed Laser Photodeposition (PLP) of a-Se from aqueous colloid solutions with KrF laser at a wavelength of λ=248nm has
been performed. Nanometer thick layers were obtained on quartz substrates in contact with the solution for various Pulse Numbers
(PN). Amorphous Se layers, 5–20nm thick, were obtained typically by 50–500 laser beam pulses of 7(nsec) duration delivered
at RR=1Hz with a total fluence of 370mJ/cm2. The deposited nanometer morphology was analyzed by a Differential-Evanescent Optical Microscopy method and Scanning Electron
Microscopy (SEM). The observed leaking electromagnetic field from the waveguide substrates was used to evaluate the thickness
profile and growth rate of photodeposited a-Se. Capturing the differential evanescent light leaking image, yielded the PLP
nanostructures profiles in the deposited zone. Using this technique in combination with SEM microscopy allowed us to estimate
the structural properties of the ultra-thin a-Se nano-structures.
Journal of Materials Science Materials in Electronics 04/2012; 18:207-211. · 1.49 Impact Factor
[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. · 1.55 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. · 1.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: Thin AlN films were synthesized by pulsed laser deposition at 800 °C
by a KrF* excimer laser source (λ = 248 nm, τ = 25 ns, 3 Hz)
at fluences of 4.8, 8.6 and 10 J/cm2 in nitrogen ambient at a
dynamic pressure varying from 0.1 to 10 Pa. The film microstructurewas
studied by X-ray diffractometry, while the film surface morphology of
AlN films was examined by AFM imaging. At the low laser fluence (4.8
J/cm2), a stable hexagonal AlN phase was formed, while at the
intermediate laser fluence (8.6 J/cm2), both hexagonal and
metastable cubic crystallites were observed. At the high laser fluence
(10 J/cm2), the films were "XRD amorphous". The surface
roughness shows a tendency to increase with the increase in the nitrogen
pressure. The root-mean-square roughness values are 0. 2 - 5 nm,
depending on N2 pressure.
Journal of Physics Conference Series 03/2012; 356(1):2003-.
[show abstract][hide abstract] ABSTRACT: AlN films doped with Si (AlN:Si) were synthesized on p-Si(100) substrates by pulsed laser deposition. Al-AlN:Si-Si metal-insulator-silicon (MIS) structures were formed and their current-voltage characteristics measured at 77 K and 290 K were analyzed. The results revealed that the charge transport is carried through the AlN:Si-Si MIS structures by the mechanism of trap space charge limited current.
Journal of Physics Conference Series 01/2012; 356(1).
[show abstract][hide abstract] ABSTRACT: We report on the deposition of triacetate-pullulan polysaccharide thin
films on drug pellets (diclofenac sodium) by matrix assisted pulsed
laser evaporation method. The radiation generated by a pulsed excimer
KrF* laser source (λ = 248 nm, τ = 20 ns) operated at 2 Hz
repetition rate was used for ice targets evaporation. The timed -
controlled drug delivery was proved by spectroscopic in vitro studies
and in vivo anti-inflammatory investigations on rabbits. We showed that
the coating of drug pellets with triacetate-pullulan thin films resulted
in the delayed delivery of the drug for up to 30 min.
[show abstract][hide abstract] ABSTRACT: This paper studies optical, chemical and photoinduced changes in amorphous As–S films, obtained by nanosecond pulsed-laser ablation of a As40S60 target. The arsenic content of the films is slightly higher than the target composition and depends on the ablation fluence. The photobleaching phenomenon appears after 1–2 min of bandgap laser irradiation. The refractive index diminishes by 0.07 and the transmission approximately doubles. It was established for the first time that films obtained by pulsed laser deposition exhibit a positive resist behavior in amine-containing etchant. The etching rate of the irradiated film was 0.12 mm/min, while as-deposited films have lower etching rate. The measured selectivity rate was of 14:1. A 2D high-quality hole array was produced by direct laser writing and further etching. The unusual behavior can be a result of different glass network formation during the condensation of AsS n molecules sputtered from the bulk target. This is different from the case of thermally evaporated films where AsS 1 molecules only were identified in gas-phase by mass spectrometry. ß 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction Chalcogenide vitreous compounds comprise a large group of materials with promising application in photonics and optoelectronics due to high VIS–IR optical transparency, photoinduced phase change, optical absorption modification by laser beam, photo resist properties, high third-order nonlinearity, etc. [1, 2]. As compared to organic resists, which have low (1.4–1.5) refractive index, chalcogenide compounds have a high value, around 2.5, of the refractive index that allows the design of 2D/3D photonic crystals with full open bandgap [3, 4]. Different studies reported investigations of 2D photonic structures  or channel waveguides [6, 7] based on chalcogenide glasses. Far less they were done on silicon wafers  that have especial interest, the possibility of integration of microelectronic and optoelectronic devices. Zakery and coworkers [9, 10] realized chalcogenide As–S films by ultrafast PLD. The depositions were performed using the second harmonic of a mode-locked Nd:YAG laser (l ¼ 532 nm, t p ¼ 50 ps) at a 76 MHz repetition rate. The pulse energy of %80 nJ was very small and allowed high-quality and low-loss waveguide
physica status solidi (a) 01/2012; 209(11):2173-2178. · 1.21 Impact Factor