National Institute Of Materials Physics - Romania

The paper presents the effect of additives on nickel nanowires preparation by employing a template approach. The nanostructures were obtained by electrochemical deposition in ion track nanoporous membranes. The main goal was to find a wetting agent which increases the pores filling efficiency. Due to the fact that the polycarbonate nanoporous membranes used as templates are strongly hydrophobic problems appear when filling the nanopores with the aqueous electrochemical baths. We found that polyvinylpyrrolidone (PVP) added in the bath improves membrane wetting, thus increasing the deposition efficiency up to 80%. Electrochemical polarization and chronoamperometry were employed for identifying and studying the processes which take place in the case of cathodic deposition of nickel nanowires. Scanning electron microscopy was employed for nanostructure morphology characterization.

We investigate the measurement induced dephasing of the Fano effect in the electronic transport through a double quantum dot mesoscopic interferometer coupled to a charge detector. The current and the differential conductance are computed within the Keldysh formalism, taking into account of the inelastic processes due to the dot-detector interaction. We show that the visibility of the Fano lineshape is reduced by applying a finite bias on the charge detector. (C) 2007 Elsevier B.V. All rights reserved.

In this paper we present the preparation and biological tests of iron oxide nanoparticles coated with dextrin. Iron oxide was also prepared by co-precipitation. The samples were characterized by transmission electron microscopy (TEM) and 14 scanning electron microscopy (SEM). Biocompatibility test of the iron oxide nanoparticles coated with dextrin substrate has been done using primary osteoblast cell line. After osteoblast culture achievement, the cells were treated with trypsin 0.05% and splitted in 35/35 mm Petri dish. The influence in vitro was assessed using primary osteoblast cell line and various techniques to observe cell-particles interactions. The results of these analyses are presented in this work.

Nickel nano- and micro- tubes were prepared by electroless deposition in ion track template membranes. By choosing the appropriate etching conditions membranes with cylindrical or conical pores were obtained allowing the preparation of cylindrical or conical tubules. The activation of the membranes was a two step process. The bath used for deposition was an acidic one. Typically for acidic bath deposition, by energy dispersive X ray analysis, a phosphorous content of up to 10 % was found in the deposit.

Compactness of microstrip antennas has made them very attractive for applications in communication systems. As the need for antenna miniaturization continues, a possible solution is offered by the utilization of high dielectric constant materials as substrate. The purpose of this paper is the study of patch antennas on high permittivity dielectric substrates (Zr-0.8 Sn-0.2)TiO4 - ZST. A comparative investigation of different types of patch and arrays was performed Two substrate thickness h(1)=1 mm and h(2)=2 mm at a frequency of f=1090 MHz was considered. The main advantage of ZST material as a dielectric substrate for patch antennas is the miniaturization of the antennas as well as a high stability with the temperature. For each case we presented the radiation pattern, the efficiency and the input impedance of the patch antennas. The patch antennas were designed using an improved cavity model (a further improved Richards cavity model). The radiation pattern for rectangular array with n = 4, 16, 32 are also presented. The numbers are imposed by the feeding system of the array, which must ensure the same phase for all the patches. A discussion on the suitability of patch antennas with high permittivity substrate is done.

Creatinine thin films were synthesised by matrix assisted pulsed laser deposition (PLD) techniques for enzyme-based biosensor applications. An UV KrF* (lambda = 248 nm, tau similar to 10 ns) excimer laser source was used for the irradiation of the targets at incident fluence values in the 0.3-0.5 J/cm(2) range. For the matrix assisted PLD the targets consisted on a frozen composite obtained by dissolving the biomaterials in distilled water. The surface morphology, chemical composition and structure of the obtained biomaterial thin films were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, and electron dispersive X-ray spectroscopy as a function of the target preparation procedure and incident laser fluence.

Photoluminescence properties of Er3+-doped calcium niobium gallium garnet (CNGG) disordered crystals have been studied in the range of 200-2000 nm at 10-290 K. In addition to emission bands due to Er3+, a broad emission band is observed at 470 nm. From the emission spectra that were obtained by various excitations, level assignment has been established for the emission bands. Different temperature dependences are observed between the emission bands at 522 and 543 nm. This is explained using non-radiative phonon relaxation between the H-2(11/2) and S-4(3/2) states. Besides the 1535 nm Er3+ emission band, near infrared emission bands are observed at 860 and 1240 nm, which are attributed to the transitions from the S-4(3/2) state to the (4)vertical bar(13/2) and vertical bar 4(11/2) states, respectively.

The paper reports the first observation of cooperative optical absorption and emission processes in Yb3+:Sc2O3 transparent laser ceramics. The intensity of cooperative processes in highly transparent ceramics Yb3+:Sc2O3 with up to 30 at.% Yb scales well with the data existing on single crystals and indicates that the distribution of the Yb3+ ions is random, without regions of agglomeration. (c) 2007 Published by Elsevier B.V.

The nano-crystalline PbS/n-Si heterostructure was studied using photocurrent spectra, I-V and C-V characteristics and admittance spectroscopy. The frequency dependent junction capacitance and conductance measurements show the presence of two contributions: first, a defect related mechanism which we attribute to a deep trap level with a large cross-section in nano-crystals with smaller sizes around 5 nm at the interface with Si and a second mechanism with an activation energy of about 250 meV, attributed to carrier transport in relatively large PbS grains of about 15 nm in size. (c) 2007 Elsevier B.V. All fights reserved.

We study the effect of annealing on structure, morphology and optical properties of nanocrystalline films of GaN, GaN:O and GaN:Mn prepared by ion assisted deposition on silicon, quartz and glassy carbon substrates. Blisters and holes having diameters proportional with the thickness of the film were observed in GaN:O deposited on silicon and glassy carbon. The Mn excess in GaN:Mn turns through annealing into MnxNy islands. The degree of short- and intermediate-range order in the films was investigated by micro-Raman spectroscopy, extending to about 3 nm for gallium oxynitride films annealed to 973 K and to more than 10 nm in GaN samples. A diminished oxygen content following the annealing procedures on GaN:O samples is noticed from the reduced intensity of the oxygen mode at 1000 cm(-1) in the Raman spectra. This observation is supported with X-ray photoemission spectroscopy measurements. The presence of oxygen at concentrations above 15at.% in the films leads to an abrupt nanocrystalline-amorphous transition. (C) 2007 Elsevier B.V. All rights reserved.