Aggregated systems of silver (Ag) and gold (Au) nanoparticles coated with cationic polythiophene were prepared, which showed optical properties typical for strongly coupled plasmonic excitations. The procedure allowed tune up the three-dimensional arrangement of nanoparticles assembly for achieving strong SERS effect at the excitation wavelength depending on the polymer concentration. By combination with an anionic derivative of polythiophene thin multilayer films composed of alternating anionic and cationic polythiophene with mutually interacting plasmonic Au nanoparticles were successfully prepared using layer-by-layer deposition.

An electron diode having a ferroelectric plasma cathode (FPS) controlled by optic fibers was operated at a repetition rate of 0.5 Hz during 1 hour, when an accelerating pulse of ~250 kV in amplitude and ~250 ns in duration is applied. The application of the fiber optic decoupling allows easy control and synchronization of the FPS operation with the firing of the HV generator. It was shown that the use of the FPS with fast fall time of the driving pulse allows reproducible generation of an electron beam having a current amplitude of ~1 kA and uniform cross-sectional current density distribution. It was shown also that in the case of the driving pulse ringing, the application of the accelerating pulse during the fall in the negative ringing leads to a plasma pre-filled mode of diode operation due to intense ion emission from the FPS. When the accelerating pulse is applied during the rise in the positive driving pulse ringing, one obtains diode operation with limited plasma emission ability. Only when the accelerating pulse is applied during the fall in the positive ringing of the driving pulse does one obtain diode operation in space-charge limited mode. This dependence of the diode operation on the timing of the accelerating pulse application with respect to the driving pulse is explained by processes related to the screening of ferroelectric bounded surface charges by the plasma charged particles.

Electrical measurements of Se $_{98-X}$ Zn2InX (X = 0, 2, 4, 6 and 10) chalcogenide glasses have been carried out at room temperature. I-V characteristic of the present glasses were recorded upto 200 V. A drastic changes in I-V characteristic have been observed between 180 to 200 V for 4, 6, 10 at% of indium. The composition dependence of electrical conductivity is also discussed.

Heteroepitaxial GaN layers grown on sapphire by metal organic vapour phase epitaxy (MOVPE) have been characterised by conventional transmission electron microscopy (TEM) on planar and cross-sectional samples, Large Angle ConvergentBeam Electron Diffraction (LACBED) and by high-resolution transmission electron microscopy (HRTEM). Hollow tubes termed nanopipes were resolved on planar view and cross-sections of heteroepitaxial GaN. For advanced studies of the nature of nanopipes the LACBED method was employed. The recognition between perfect structure and screw distortion around nanopipes was performed with high accuracy using Zone Axis LACBED images.

The effects of turbulence on momentum, heat and solutal transport in a typical high power laser surface alloying process are numerically investigated. The turbulent transport is accounted for by employing a standard high Reynolds number k − ε model, suitably modified to take into account a dynamic evolution of the phase changing interfaces. Phase transitions are handled by using a modified enthalpy porosity technique. Diffusive effects associated with turbulence are found to significantly affect the momentum and solutal transport in the molten pool. On the other hand, enhancements in thermal diffusion on account of turbulence turn out to be rather marginal, with the molecular and eddy thermal diffusivities approximately of the same order. The generation and dissipation rates of turbulent kinetic energy are shown to be in local equilibrium. Based on this inference, a scaling analysis is also performed, which provides order of magnitude estimates of melt pool penetration, mean surface velocity, and temperature/concentration scales. The above estimations are found to be in good agreement with numerical simulation results, in an order of magnitude sense.

SrTiO3 had been often tentatively used as an insulating barrier for HT superconductor/insulator heterostructures. Unfortunately, the deposition of SrTiO3 on the YBa2Cu3O7 inverse interface results in a poor epitaxial regrowth producing a high roughness dislocated titanate layer. Taking into account the good matching with YBa2Cu3O7 and LaAlO3,CeO2 and Ce1−x Mx O2 (M = La, Zr), epitaxial layers were grown by pulsed laser deposition on LaAlO3 substrates and introduced into YBa2Cu3O7 based heterostructures as insulating barrier. After adjusting the growth parameters from RHEED oscillations, epitaxial growth is achieved, the oxide crystal axes being rotated by 45° from those of the substrate. The surface roughness of 250 nm thick films is very low with a rms value lower than 0.5 nm over 1 μm2. The YBa2Cu3O7 layers of a YBa2Cu3O7/CeO2/YBa2Cu3O7 heterostructures grown using these optimized parameters show an independent resistive transition, when the thickness is larger than 25 nm, respectively at T c1 = 89.6K and T c2 = 91.4K.

The effect of aluminum gettering on different silicon materials used for solar cells has been investigated by means of microwave photoconductivity decay (μ-PCD) and electron beam induced current (EBIC). μ-PCD measurement revealed that the lifetime of multicrystalline silicon (mc-Si) with a lower initial lifetime could be increased by high temperature gettering (1000 °C), while that of mc-Si with a higher initial lifetime could not be increased, but was even degraded. EBIC results revealed that no significant improvement of diffusion length was observed in both contaminated and uncontaminated wafers, while 850 °C Al gettering was employed. It is concluded that both the initial material quality and the thermal treatment have influences on the effect of Al gettering. In addition, dislocations with bright EBIC contrast were discovered in annealed mc-Si wafers, the origin of which is discussed.

Highly crystalline core-shell FeCo-CoFe2O4 nanowires were obtained from a three step process. Initially, CoFe2O4 nanowires were grown using electrospinning and annealing at higher temperatures. Through a thermal reduction under controlled conditions, CoFe2O4 nanostructures were converted to FeCo alloy nanowires. Then by natural oxidation, a highly crystalline shell of CoFe2O4 formed over the FeCo core structure. Structural and magnetic characterizations revealed the presence of highly crystalline FeCo-Co2FeO4 core-shell structure. Magnetically, the soft FeCo phase switches at a lower magnetic field compared to the hard CoFe2O4 phase, yielding an irregular hysteresis loop with a squeezed loop in the middle. The FeCo/CoFe2O4 core-shell is stable and it retains its structure for a prolonged duration.

A binary Sn-5wt.%Sb solder alloy was chosen as a potential alternative to Sn-Pb solder alloy to be subjected to many studies. It was casted from the liquid state, cold drawn into wires of 1 mm diameters. The study includes the structure, electrical resistivity, tensile strength, hardness and indentation creep behavior using XRD, four probes electrical circuit, conventional tensile testing machine, Vickers microhardness tester, respectively. These properties were carried out for the cold worked alloy and after annealing at 393 and 473 K for 60 min. It was found that annealed samples exhibit more precipitations of the intermetallic compounds SnSb, higher lattice parameters and higher crystallite size, while have lower lattice-strain induced due to the cold working process. These structural changes greatly affect the electrical resistivity and mechanical properties of this alloy.

Anisotropic etching of silicon is achieved in the presence of ultra-violet exposure in a solution containing hydrofluoric/nitric/acetic acids (HNA). The HNA solution is typically used for polishing silicon and etching polysilicon due to its isotropic etching property. In the technique proposed in this paper which is called UV-HNA, the etching of silicon is enhanced in the direction determined by UV exposure. A mixture of HF/HNO3/CH3COOH with a relative composition of 1:15:5 seems suitable for revealing 〈111〉 planes with an etch rate of 10 μm/h at 35 °C. The bottom of the etched craters is hillock-free and etch rates as high as 60 μm/h can be achieved using higher concentration of HF acid in HNA solution. In the latter case the etching is more isotropic and mask undercut is observed. Also membranes with a depth of 400 μm are fabricated on n-type Si 〈100〉 with a thickness of 500 μm by means of standard 34 wt% solution of KOH at temperature of 60 °C. Problems encountered during the experiment, and their solutions are discussed and results of these experiments are reported.

This article presents a time domain discontinuous Galerkin method applied for solving the con-servative form of Maxwells’ equations and computing the radiated fields in electromagnetic compatibility problems. The results obtained in homogeneous media for the transverse magnetic waves are validated in two cases. We compare our solution to an analytical solution of Maxwells’ equations based on characteristic method. Our results on shielding effectiveness of a conducting wall are same as those obtained from analytical expression in frequency domain. The propagation in heterogeneous medium is explored. The shielding effectiveness of a composite wall partially filled by circular conductives inclusions is computed. The proposed results are in conformity with the classical predictive homogenization rules.

Structural antiferrodistortive phase transitions have been studied in mixed disordered perovskites Rb1−x Kx CaF3 crystals over a wide concentration range (0 < x < 1) by Raman spectroscopy and a full group theory analysis has been carried out. Raman spectra have been indexed in all phases and a “one mode” behavior is evidenced. The influence of the cationic substitution on the mechanism driving the transitions is characterized by: i) the disappearance of the strong first-ordercharacter of the low temperature transition in RbCaF3; ii) the continuous evolution of the Raman spectra as a function of temperature, with no sharp indication of a transition except for the classical soft mode behavior; iii) the persistence of hard Raman modes even in the ideal cubic phase; iiii) the appearance of a broad central component associated with relaxation processes. Finally, the results of lattice dynamics calculations, when compared to inelastic neutron scattering measurements, show that the classical virtual crystal model fails. These results are examined in terms of a simple displacive transition for these fluoro-perovskites in which the interactions between F6 octahedra are anisotropic and the importance of the substitutional disorder is highlighted.

The heating rate effects in simulated liquid Al2O3 have been investigated by Molecular Dynamics (MD) method. Simulations were done in the basic cube under periodic boundary conditions containing 3000 ions with Born-Mayer type pair potentials. The temperature of the system was increasing linearly in time from the zero temperature as $T(t)=T_0 +\gamma t$ , where $\gamma $ is the heating rate. The heating rate dependence of density and enthalpy of the system was found. Calculations show that static properties of the system such as the coordination number distributions and bond-angle distributions slightly depend on $\gamma $ . Structure of simulated amorphous Al2O3 model with the real density at the ambient pressure is in good agreement with Lamparter's experimental data. The heating rate dependence of dynamics of the system has been studied through the diffusion constant, mean-squared atomic displacement and comparison of partial radial distribution functions (PRDFs) for 10% most mobile and immobile particles with the corresponding mean ones. Finally, the evolution of diffusion constant of Al and O particles and structure of the system upon heating for the smallest heating rate was studied and presented. And we find that the temperature dependence of self-diffusion constant in the high temperature region shows a crossover to one which can be described well by a power law, $D\propto (T-T_c )^\gamma $ . The critical temperature T c is about 3500 K and the exponent $\gamma $ is close to 0.941 for Al and to 0.925 for O particles. The glass phase transition temperature T g for the Al2O3 system is at anywhere around 2000 K.

The variable angle spectroscopic ellipsometer in conjunction with computer simulation were employed to determine the optical constants of ZnO in the ZnO/Ag/ZnO (ZAZ) multilayer system. A five-phase, glass/ZnO/Ag/ZnO/air, model was used to fit the calculated data to the experimental spectra. The ellipsometrically determined ZnO and Ag layers thicknesses were found to be agreed well with those previously determined by X-ray reflectivity. The effects of Ag layer thickness (Agd ) and ZnO top layer thickness (ZnOd ) on the optical constants of ZnO in the ZAZ multilayer system were discussed. The refractive index values determined at 550 nm, remains almost constant as Agd increases while the refractive index values decrease with decreasing ZnOd . Over the whole visible spectral range the extinction coefficient values of the Agd group are very close to zero and does not depend on Agd while the extinction coefficient values of the ZnOd group increase with decreasing ZnOd . The optical band gap values are found to be affected strongly by both Agd and ZnOd .

This contribution presents an application of scanningnear-field optical microscopy to the characterization of semi-conductors.It is based on the photocurrent mapping of a patterned Au/GaAs structure(Schottky barrier) under local illumination by the nanosource. The resultsobtained with different wavelengths, metallized or dielectric probes anddifferent bias voltages exhibit photocurrent variations independent of the topography and induced by interface defects. Finally, from this study ofa patterned planar structure, we propose a method to determine the meanfree path of the charge carriers in the volume.

We have observed ultraviolet photosensitive properties ofSrTiO3 single crystals. The photoresponse signal reaches 7.6 mVunder a bias voltage of 110 V and an on-sample energy of 250 nJ fora 15-ps-duration 355 nm laser pulse. A linear relationship isobtained to the peak signal as a function of bias without anysaturation trend from 1 to 110 V. Ultrafast characteristic as afunction of time was also presented with the rise time as short as750 ps. Furthermore, a weak photoresponse was detected with a largebias of 2.5 kV under a 420-nm-wavelength laser pulse due to bandedge tilting, and drop three orders of magnitude than that under the355 nm laser pulse, indicating the setup consisting of SrTiO3single crystal is suitable for detecting ultraviolet radiation.

In this work the surface of (4 0 0) p-type Si wafers is bombarded with 29 keV nitrogen ions at various ion beam fluency varied from 1016 to 1018 ions/cm2 and the results are investigated. Si3N4 film with orthorhombic structure is formed on silicon surface with cubic structure while the lattice parameter of the generated layer is not affected by change of nitrogen ion beam dose. RMS roughness of implanted samples increases by increasing the nitrogen dose, specially when the dose is more than 3×1017 ions/cm2. Surface resistivity of samples is increased by increasing the dose of ion beam. Although changes in the transmission of implanted samples does not differ very much in comparison with row sample but reflection of implanted samples decrease about 60% for the electromagnetic wave in the range of 200 to 1500 nm. Absorption coefficient of samples is obtained and the band gap energy of samples is calculated. It is observed that formation of defect levels changes the magnitude of band gap energy.

Trap parameters in poly(1-(3,4-difluorophenyl)-2-(4-pentylcyclohexylphenyl)acetylene) (PDPA-2F) based devices have been investigated by using the thermally stimulated current (TSC) technique. The device structure is ITO-PEDOT-(PDPA-2F)-M, where M stands for the cathode metal (Al, Ca/Al, and Au). The results reveal at least three TSC peaks in devices denoted as peaks A, B and C. Comparing trap parameters in ITO-PEDOT-(PDPA-2F)-Au hole-only device and ITO-PEDOT-(PDPA-2F)-Ca Al (Al) bipolar devices, we assigned A and B trap types to hole-like traps and C type traps to electron-like traps. The trap densities are in the range of 1015−1017 cm−3 and the trap levels are 0.12 eV (A type traps), 0.36 eV (B type traps), and 0.25 eV (C type traps).

This paper discusses some aspects of n-hexane soot reactivity in a multi-pin to plate pulsed corona discharge working in the nanosecond regime at atmospheric pressure. The soot-discharge interaction was quantified by measuring the densities of CO, CO2, O3 and NO2 out-coming from the discharge cell. Results showed that CO2 is the major product of soot oxidation. They also showed a strong enhancement of soot oxidation for O2 percentage greater than 10% and cathode temperatures above 425 K. The soot reactivity is significantly enhanced when the discharge frequency is increased. The results obtained were interpreted in term of the competition between the kinetics of plasma active species adsorption and oxidation product desorption.

In the first part of this work the regime of the DC electrical discharge in nitrogen, in absence and in presence of polystyrene thin films in the cold plasma reactor, for a constant gap length d = 1 cm and for variable pressures ( $1~{\rm~mbar} < p < 10~{\rm~mbar}$ ) is characterized, while the gas flow rate is maintained at Q = 1 sccm. V-I curves underline that in any case a “normal glow-like” discharge is established. Experimental results bring out that the presence of the films in the volume of the produced plasma seems to modify the structure and some of the discharge characteristics, like the cathode secondary emission effects. V-I curves ( $I <200~\mu$ A), discharge repetitive current impulses, discharge repetitiveemitted light impulses along the discharge symmetry axis and photos of the discharge, inpresence and in absence of the films, are presented. In the second part of this paperresults of polystyrene thin films treatment under the above DC “normal glow-like”discharge regime in nitrogen for improving the wettability of the films are presented. Theeffect of discharge main parameters (pressure p and mean current I through thedischarge) on the treatment is studied under certain experimental conditions. The wettabilityis characterized by contact angle measurements using deionized water drops and the evolutionversus the treatment time t tr of the $\Delta \theta/\theta_{\rmi}=(\theta_{\rm i}-\theta_{\rm f})/\theta_{\rm i}$ ratio ( $\theta_{\rm i}$ : the contact anglebefore the treatment and $\theta_{\rm f}$ : the contact angle after the treatment) isestimated. It is deduced that optimizing main parameters of the DC electrical discharge innitrogen it is possible to obtain films with very good wettability (suggestively $\Delta\theta/\theta_{\rm i}=0.951$ corresponding to $\theta_{\rm f}=4^{\circ}$ , at p = 4 mbar, $I=200~\mu$ A, $t_{\rm tr}\cong 600$  s). A rapid change of the films surfacenature ( $0~{\rm s} < t_{\rm tr} < 60$  s, suggestively) seems to be followed by a slower oneand finally by a saturation. The gas pressure and the discharge mean current seem to play avery important role for the treatment. The experimental results allow us to start adiscussion about the possible role of some active particles produced in the plasma to thetreatment of the films and especially the role of the neutrals and the metastables.