The electrical and photovoltaic characteristics of thermally evaporated thin films of 4-tricyano-vinyl-N,N-diethylaniline sandwiched between indium tin oxide and aluminium has been investigated. Dark current density-voltage characteristics under forward bias are found to be due to thermionic emission conduction at lower voltage region. While, at higher voltage region there is space-charge-limited conduction controlled by exponential trap distribution above the valance edge. Reverse bias curve is interpreted in terms of Poole-Frenkel effect. The device exhibits photovoltaic characteristics when it illuminated through Al electrode. The typical photovoltaic parameters were estimated at room temperature and under light illumination with an input power density of 80 mW/cm−2.

Glow discharges of oxygen and nitrogen were applied to low density polyethylene thin films in order to study accelerated oxidation and nitridation in the polymer. The studies were focused on the morphologic, crystalline and hydrophilic evolution promoted by plasma exposure. The particular chemical characteristics of the gases and the constant impact of high-energy particles on the surfaces produced different types of erosion. Oxygen plasmas produced the release of fragments from the polymeric surface which created fibered textures and nitrogen plasmas resulted in folded morphologies of nano and micro dimensions on polyethylene. The plasmas of both gases increased and decreased the crystallinity in the polymers, between 33% and 57%, with similar tendencies, differing only in the percentage of crystallinity. The plasma exposure produced a decrease in the contact angles of water on polyethylene in the first 30 min of plasma, from 70% in the untreated polymers, to 45% and 35% as a consequence of the polar groups added to the surface.

Following the concept of remote circular electromagnetic cloaks [Phys. Rev. Lett. 102, 093901 (2009)], here we exploit theoretically a class of rectangular cloaks that can acoustically cloak an object outside the cloaking shell. The cloaked object is no longer deafened by the cloaking shell, which is distinctly different from the existing acoustic cloaks. The function of such cloaks is justified by full wave simulations based on the finite element method. This work makes it possible to propose some applications like the stealth of submarines, which receive any incoming acoustic waves while keeping themselves undetectable to enemy's sonar devices.

Phase diagram of a ferroelectric thin film with two surface layers is studied in frame of the effective field theory (EFT) of transverse Ising model (TIM). The surface of the system is formed from two layers characterized by the exchange interaction anisotropy $R_s =\frac{J_s }{J}$ and the transverse field $\Omega _{s}$ . The crossover from the ferroelectric phase (FP) to the paraelectric phase (PP) is discussed. The phase diagram of the system is studied in $\big( {\frac{K_B T_c }{J},\frac{\Omega _s }{J}} \big)$ coordinates as function of the thickness parameter L. The special attention is given to the effect of the transverse field $\Omega _{s}$ on the phase transitions.

Nanocrystalline silicon films were deposited by a picosecond laser ablation on different substrates in vacuum at room temperature. A nanocrystalline structure of the films was evidenced by atomic force microscopy (AFM), optical and Raman spectroscopies. A blue shift of the absorption edge was observed in optical absorption spectra, and a decrease of the optical phonon energy at the Brillouin zone centre was detected by Raman scattering. Early stages of nanocrystalline film formation on mica and HOPG substrates were studied by AFM. Mechanism of nanocrystal growth on substrate is discussed.

Thin films of titanium, copper and silver with various roughnesses were prepared by physical vapour deposition technique: dc magnetron sputtering. By varying the deposition time from few minutes to one hour it was possible to obtain metallic films with surface roughness average ranging from 1 to 20 nm. The wettability of these films was studied by measuring the contact angle using the sessile drop method and surface forces were investigated using the atomic force microscopy (AFM) by measuring the pull-off force between the AFM tip and the surfaces. Experimental results have been mainly discussed in terms of metal surface reactivity, Young modulus of the materials and real surface of contact between the AFM tip and the film surfaces.

Regular patch arrays of random gold nanostructures were fabricated by electrochemical deposition of nanowires in ion track-etched templates. During ion irradiation with GeV ions of fluence 106, 107, or 108 cm−2, a shadow mask was used resulting in templates structured with square arrays of 50 μm holes and 100 or 150 μm pitch. The Au nanowires grown in the track-etched pores had a length of 7–28 μm and a diameter of ~300 nm, and were either solitary or clustered after template dissolution. The structured wire ensembles were systematically investigated with scanning electron and field emission scanning microscopy. Field emission with about 90% efficiency was achieved for wide-spaced patch arrays with medium and high number of Au nanowires at 1500 V for 20 μm anode distance. The current carrying capability of the patches strongly varied between 40 nA and 90 μA. The corresponding processing effects are correlated to adsorbates and nanostructural changes of the wires which give suitable hints for the optimization of structured Au nanowire cathodes.

Titanium-doped LiCoO2 thin films were grown by pulsed laser deposition technique on silicon substrates. Structure, AFM, FTIR, Raman and Optical properties were studied with respect to their deposition parameters i.e. substrate temperature $(T_{s})$ and oxygen partial pressure $(p_{{\rm O}_{2}})$ in the deposition chamber. The films deposited in $p_{{\rm O}_{2}}= 100$  m Torr showed good crystallinity on silicon substrates maintained at $T_{s}= 700$  °C. It was found that such a film crystallizes in the layered α-NaFeO2 structure. The influence of titanium doping on particle size and morphologies has been clearly studied. FTIR spectra displayed the characteristic IR dominant bands at 246 and 550 cm−1 for titanium doped LiCoO2 thin films. The Raman peaks observed for the films at 594 cm−1 and 485 cm−1 are ascribed to Raman active modes A1g and Eg respectively. The influence of titanium doping on the physical properties has been systematically studied.

Thin films of head-tail (H-T) regio-regular poly[3-(4-octyloxyphenyl) thiophene] (POOPT) were grown using the MAPLE (Matrix Assisted Pulsed Laser Evaporation) technique in which the target is a frozen solution of the polymer in chloroform. Target evaporation was obtained by laser irradiation at 1064 nm and substrates were kept at different temperatures. Information concerning the preservation of the polymer local chemical structure following laser irradiation was obtained by FTIR (Fourier Transform InfraRed) spectroscopy. Based on FTIR data, the chemical structure of the deposited polymer seemed to undergo little or no damage. From UV-Visible spectroscopic analysis, it turned out that the degree of order of the film is strongly affected by the substrate temperature: the polymer was deposited in a disordered form on the substrate at room temperature whereas on the hot surface we locally obtained the π-stacked structure characteristic of polythiophenes. Atomic force microscopy (AFM) images showed that the polymer formed aggregates of different dimensions (<1 μm to 5 μm) with a columnar shape and showed micrometric domains with sharp and apparently regular edges for the film grown on a hot substrate.Electrical measurements performed by a standard two-probe technique confirm that the structural order degree strongly affects the film charge transport properties.

Electrical and magnetic properties were studied for evaporated Fe thin films on glass and Si substrates. These properties were investigated by means of the four point probe and the magneto-optical Kerr effect techniques. Rutherford backscattering (RBS) and scanning electron microscopy (SEM) experiments show no interdiffusion at the interface Fe/Si for these samples. The electrical resistivity $\rho $ is found to be larger in Fe/glass than in Fe/Si for the same thickness. Diffusion at the grain boundaries seems to be the dominant factor in the $\rho $ values in this 6 to 110 nm thickness range; the reflection coefficient is smaller in Fe/glass (R ≈ 0.40) than in Fe/Si(100) (R ≈ 0.65). Saturation field and strain values confirm that Fe films have a stress induced magnetic anisotropy. Coercive field H C values range from 2.45 Oe for Fe/Si(100) to 17.65 Oe for Fe/Si(111) for the same Fe thickness (45 nm).

Fe-Cu alloys were grown on polycrystalline titanium substrates after determining the suitable deposition potentials. Based on the results obtained from cyclic voltammetry curves, a potential region between –1.8 V and –2.3 V vs. saturated calomel electrode (SCE) was selected. During growth, the electrochemical characterizations of the films were made by recording the current-time transients. The structure of films becomes more brittle with the increase of the deposition potential over –2.3 V vs. SCE due to extreme hydrogen liberation from cathode surface. The structural analysis by the X-ray diffraction demonstrated that the films have a typical body centered cubic of $\alpha $ -Fe preferentially grown in the (211) direction. The grain sizes, lattice parameters and interplanar spacings were also calculated. Energy dispersive X-ray spectroscopy measurements demonstrated that the ratio of Fe:Cu was almost the same. The magnetic analysis by vibrating sample magnetometer indicated that the coercivity of the films was slightly affected by the deposition potential.

Zinc nitride (ZnN) films were prepared by electron beam evaporation technique. The effect of heat treatments on the structural and optical properties of these films were studied. The as-deposited films show amorphous structure and some peaks which are related to Zn3N2 and ZnO can be observed for annealed films. The study of the optical gap shows that these films have direct optical band gap about 3.2 eV at temperature 350 °C. At high temperature, the ZnN films become more opaque and resistive. Other optical parameters such as refractive index, extinction coefficient and dispersion parameters were investigated as a function of annealing temperature.

We have fabricated and characterised colloidal silver nanoparticles by the electrical arc discharge method in DI water. Size and optical properties of the silver nanoparticles were studied versus different arc currents. Optical absorption indicates a plasmonic peak at 392 nm for 10 A which increases to 398 nm for 20 A arc current. This reveals that by raising the arc current the size of the nanoparticles increases. Optical absorption of silver nanoparticles after 3 weeks shows precipitation of them in a water medium. The effect of different surfactant and stabilizer concentrations such as cethyl trimethylammonium bromide (CTAB), polyvinyl pyrrolidone (PVP), sodium citrate, sodium dodecyl sulfate (SDS), sodium di-2-ethylsulfosuccinate (AOT) and carboxymethyl cellulose (CMC) on the stability of silver nanoparticles was investigated. The colloidal silver nanoparticles with 100 μM concentration were stable for more than 3 months at 50 μM CTAB and 6 months at 10 μM sodium citrate concentration, respectively. SEM images of the sample prepared at 50 μM CTAB concentration reveal uniform and fine nanoparticles. The mean size from TEM images is about 14 nm. TEM images of the sample prepared at 10 μM sodium citrate concentration show a shell of citrate that covers the silver nanoparticles.

Using low molecular weight polyethylenimine (PEI), transparent thin films of TiO2 nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 10 min. The effect of dip time on the growth mode and surface morphology was investigated by scanning electron microscopy (SEM) and non-contact atomic force microscopy (AFM). It was found that growth proceeds in the form of laterally broad islands in case of short dip times, and taller but laterally smaller islands in case of longer dip times. A model was proposed which describes the role of dip time on the lateral growth of TiO2 islands. Low molecular weight PEI resulted in around 25% less adsorption of PEI and TiO2 in comparison with high molecular weight PEI, but because of lower remaining ash, could be promising for dye-sensitized solar cell photoelectrode applications, in which removal of polyelectrolyte after the formation of thin film enhances the electrical properties and therefore the efficiency of solar cell.

The configurations, electronic structures and magneticproperties for M n N clusters (M = Fe, Co, Ni;n = 2−12, 14, 18) are obtained using all-electron density functionaltheory calculations at the general gradient approximation level. Ondoping an N atom into the pure M n clusters, theground-state structures, binding energies of the resulting mixedclusters have changed but the average M–M bond lengthdoes not obviously change except for Fe2N, Co7N and Ni7N.The doping N atom prefers surface sites except for n = 14 and 18.The results also show the enhanced stability for M n Nclusters compared with that of the corresponding pure M n clusters. The large energy gaps between the highest occupiedmolecular orbital and the lowest unoccupied molecular orbital forFen N (n = 6,12), Con N (n = 3,5,7,9,11) and Nin N(n = 3,6,11,14) clusters indicate their high chemical inertness.Moreover, it has also been found that the total spin magneticmoments of all the M atoms increase slightly for: M =Fe, n = 9,12,14; M = Co, n = 8,9,11,18; and M = Ni,n = 3,11,12.

We consider an elongated printed circuit board (PCB) whose long edges are support-free and the short edges are either simply supported or rigidly clamped. The board experiences a significant impact loading applied to the short edges. In such a situation the reactive in-plane (“membrane”) forces (stresses) are large and result in a geometrically nonlinear dynamic response of the board. The analysis is limited to the fundamental mode of vibrations, and the method of principal coordinates is used to evaluate the dynamic response of the board. The objective of the analysis is to find out if it is sufficient to consider the nonlinear behavior of the principal coordinate (because of the in-plane stresses) only, or it is necessary to account also for the effect of these stresses on the coordinate function. Based on the developed simple and physically meaningful analytical (“mathematical”) stress model, we conclude that the effect of the in-plane tension on the coordinate function does not have to be considered for a simply supported board, but has to be accounted for in the case of a clamped board. This could be done, if necessary, using the results of the analysis.

This paper shows that a suitable design of a corrugation-pitch-modulated (CPM) distributed-coupling-coefficient (DCC) distributed feedback (DFB) laser structure can strongly improve the mode selectivity $(\mathfrak{G})$ and the flatness $(\mathfrak{F})$ of DFB laser structures in order to ensure the required criteria for single longitudinal mode operation ( $\mathfrak{G}$ ≥ 0.25 and $\mathfrak{F}$ ≤ 0.05), through an extended range of current injection. It is shown that a symmetric structure should be used in order to accomplish the requirements imposed by the modern optical communication systems.Photon and carrier rate equations have been used in order to evaluate the performance of the proposed laser structure in the above-threshold regime. The variations of $\mathfrak{G}$ , $\mathfrak{F}$ , the lasing wavelength, the emitted power (P) and the side-mode-suppression-ratio (SMSR) with the current injection (I) have been evaluated.For I = 5 I th , where I th is the laser threshold current, substantial improvements in $\mathfrak{G}$ (3.8 times better), in $\mathfrak{F}$ (2 times better), in P (15% higher) and in the SMSR (about 3.4 dB higher) are achieved in the proposed CPM-DCC-DFB laser when compared to an optimised CPM-DCC-DFB laser referred elsewhere. The improvements are even better when compared to the standard QWS-DFB laser.

Semiconductor nanoparticles of ZnS:Co are synthesized by wet chemical method at room temperature. The effects of increasing cobalt ions dopant in PL ZnS particles are studied, and the distribution, absorption, excitation, emission, and structural properties of particles have been determined. XRD investigation shows the cubic structure of ZnS nanoparticles and doping has no effect on the structure and the average crystalline particle size of the doped and undoped ZnS nanometerscale samples is about 2.5 nm. TEM shows the 1–3 nm size for ZnS:Co nanoparticles. UV-visible is used to study the optical absorption of ZnS pure as well as doped nanoparticles. Furthermore, as the chemical parameters change, the size of quantum dots changes systematically. Of course, doping percentage is a significant parameter in photoluminescence properties of quantum dots, but it has no effect on the size. The maximum intensity of photoluminescence spectra obtains the at 0.1% molar of the Co dopant in ZnS:Co (Ex = 283, Em = 485.423 nm) that shows the quenching point. The intensity of the emission bands decreases with the increasing of the doping percentage continuously, which indicates that cobalt ions are the eliminators of the photoluminescence.

One-dimensional (1D) SnO2 nanowires were synthesized from SnO powder by heat treatment of SnO powder under Ar gas flow at atmospheric pressure, with the next annealing on the air at 1000 °C. The morphology and microstructure of the single crystalline SnO2 nanowires are characterized by means of the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The band gaps of the products are ~(3.42–3.78 eV) determined from UV/visible absorption spectral results. The SnO2 nanowires show stable photoluminescence (PL) with one emission peak centred at around ~2 eV.

A comparative study of the low temperature conductivity of an ensemble of multiwall carbon nanotubes and semiconductor nanowires is presented. The quasi one-dimensional samples are made in nanoporous templates by electrodeposition and CVD growth. Three different structures are studied in parallel: multiwall carbon nanotubes,tellurium nanowires, and silicon nanowires. It is shown that the Coulomb blockade regime dominates the electronic transport below 50 K, together with weak and strong localization effects. In the Coulomb blockade regime, a scaling law of the conductance measured as a function of the temperature and the voltage is systematically observed. This allows a single scaling parameter α to be defined. This parameter accounts for the specific realization of the “disorder”, and plays the role of a fingerprint for each sample. Correlations between α and the conductance measured as a function of temperature and voltage, as a function of the perpendicular magnetic field, and as a function of the temperature and voltage in the localized regime below 1 K have been performed. Three universal laws are reported. They relate the coefficient α (1) to the normalized Coulomb blockade conductance $G_{T}(\alpha)$ , (2) to the phase coherence length $l_{\phi}(\alpha)$ , and (3) to the activation energy $E_{a}(\alpha)$ . These observations suggest a description of the wires and tubes in terms of a chain of quantum dots; the wires and tubes break into a series of islands. The quantum dots are defined by conducting islands with a typical length on the order of the phase coherence length separated by poorly conducting regions (low density of carriers or potential barriers due to defects). A corresponding model is developed in order to put the three universal laws in a common frame.