In this work, we present experimental evidence and analytical studies of the XRD patterns and optical characterizations of ZnS films with different optical thicknesses. Thin films of ZnS were deposited on glass substrates by thermal evaporation. The crystallite size increased as the optical thicknesses. The overall absorbance has been increased with the film thickness and the direct band gap was obtained. It decreases with the increasing in the thickness of the films.

The characteristics of heterojunction diode pSe-nMoSe2 fabricated from thermally evaporated p-Se films on n-type Molybdenum diselenide (MoSe2) grown by direct vapour transport (DVT) technique have been examined by using current-voltage measurements. To investigate the dark current transport mechanism in pSe-nMoSe2 heterojunctions the current-voltage characteristics were measured in the temperature range 100–300 K. The prepared diode shows a rectification ratio of the order of 103 within the range –2 to 2 V. A multi-step tunnelling model was used to analyze the I-V-T characteristics of the prepared device. The activation energy determined from the saturation current was about 1.16 eV.

Black coatings are widely used in numerous applications e.g., decorative coatings, solar panels, optical instruments. The films are mostly prepared by liquid phase deposition or vapor phase deposition. In this paper we review the techniques of deposition and the properties of the most important black coatings. Optical properties are particularly presented and discussed.

The electronic structure of γ-Al2O3 and α-Al2O3 has been investigated by means of the density functional theory. A comparison of the calculation results with experimental data for amorphous alumina films is also presented. The electronic structure is described in terms of band structure and density of states. It has been found that γ-Al2O3 have similar electronic structure withα-Al2O3 and amorphous Al2O3. Effective electron masses in γ-Al2O3 as well as in α-Al2O3 equal to $m_e^\ast$ ≈ 0.4 m 0 that is in a good agreement with the experimentally found tunnel electron mass in amorphous Al2O3. The heavy holes in both alumina crystals are explained by the valence band top forming by O 2p π nonbonding orbitals.

Strontium-substituted barium vanadates, Ba5-x Srx DyTi3V7O30 (x = 0–5), were prepared by a high-temperature sold-state reaction method. The formation of the materials was checked by X-ray diffraction technique. Preliminary structural analyses of the materials exhibit the formation of new compounds in orthorhombic structure. Surface morphology of the compounds was studied by scanning electron microscopy. The effect of Sr on microstructure of the materials has resulted in a modification of the electrical properties. Study of electrical properties using impedance analysis technique exhibit (i) the presence of negative temperature coefficient of resistance behavior, (ii) presence of temperature dependent electrical relaxation phenomena, (iii) evidences of single electrical relaxation attributed to the presence of bulk contribution to the electrical properties, (iv) an enhancement in the barrier to the mobility of charge carriers on Sr-substitution. The effects of Sr in the electrical conductivity as a function of temperature at different frequency are explained in impedance spectrum analyses.

Branched treelike carbon nanotubes were grown by plasma enhanced chemical vapor deposition method on a silicon wafer. Patterned structures of as grown nanostructures were used for the fabrication of a gas sensor, which operates based on the field ionization of various gases. The variations in the electrical resistivity and the emission current of the fabricated device are related to the chemisorption and field ionization mechanisms, respectively. The sensor is capable of gas detection at room temperature and at low pressures with working at low voltages. Different gases such as H2, O2, C2H2 and Ar have been used to examine the gas sensitivity characteristics of the fabricated sensors.

High density rewritable media for near-field recording are fabricated and their writing and readout characteristics are examined. High density substrates for rewritable media are prepared using a phase transition mastering technique to overcome the limitation of the deep UV laser recorder. A cover-layer with a UV curable material is coated on the rewritable media and its surface properties are discussed to apply for cover-layer incident near-field recording configuration. The effective numerical aperture of a pick up with a solid immersion lens is 1.46, which could cope with the recording density of about 70 GB per disc. The performance of readout signals were investigated, and compared the properties between 320 nm and 200 nm of the track pitch in the substrate.

We show here that at a certain externally applied static magnetic field of moderate value, photonic band gap (PBG) is induced at optical frequencies in a stable colloidal dispersion containing a mixture of micron and nano sized magnetite spheres. The PBG is found to depend on the size of microspheres and is observed for only TM mode of the incident waves. Effect of nonmagnetic doping on the PBG is also discussed. The observed effects are attributed to the magnetically induced morphological dependent resonance (MDR) in the micron sized magnetic spheres. The technique to induce PBG may be easily amenable for lab-on-chip devices.

A multi-channeled filter that bases on the effect of photon tunneling through the coupled-cavity resonators is designed. Applying the tight-binding model and the transfer matrix method we analyze its transmission mechanism and study its transmission properties. Through the coupling of cavities, the single resonant mode is split into some discrete resonant peaks forming many transmission channels. Through adjusting the thickness of air layer we make the intervals of channelsapproximately equivalent. The whole position of channels can be moved through changing the incident angle.

Photoacoustic imaging takes the merits of simultaneous high optical contrast and low acoustical scattering, and has been proven to be a potential tool for noninvasive diagnosis of cancer tumors in an early stage. An integrated prototype multi-element synthetic aperture focusing photoacoustic imaging system using real-time digital beamformer (96 scan lines of each frame image) is designed, fabricated and tested. The combined system with multi-channel signal acquisition and real-time digital beam-formation module implements real-time dynamic receiving focus and apodization technique to process the photoacoustic signal, which is captured by a 128-element linear ultrasonic transducer array. The data acquisition and synthesis time can be accelerated in less than 4 s of each view without data average. The in vivo experiments were performed with a clear view of the blood vessels network of mouse tumor. The results demonstrate that the multi-element synthetic aperture focusing photoacoustic imaging system with real-time digital beamformer technique has the potential in the practical fast photoacoustic imaging for clinical diagnosis.

The bombardment of ions and electrons at the substrate has been studied by varying the magnetic field distribution and the grid-target distance in a triode magnetron sputtering system. The substrate temperature was correlated with the substrate current density and with the type of species bombarding the substrate. The results indicate a possibility to modify and control the bombardment at the substrate surface from predominantly electronic to predominantly ionic, which increases the substrate temperature from 383 K to 473 K, respectively.

The recent experimental observations of triple tracks in solid-state nuclear track detectors, CR-39, during Pd/D co-deposition experiments indicate that the triple tracks are due to ~14 MeV neutrons, which appear to originate from “hot” fusion reaction D(t,n)4He. Nuclear theory interpretation of the origin of ~14 MeV neutrons is presented in terms of a sub-threshold resonance reaction involving (T + p) resonance state of 4He* (J π = 0+) at 20.21 MeV, which produces 1.01 MeV T. An upper limit of the branching ratio, R(n)/R(T), between neutron production rate and tritium production rate is calculated to be R(n)/R(T) < 10-4. Experimental tests of the proposed theoretical interpretation are proposed.

Consuming chemical energy, fuel cells produce simultaneously heat, water and useful electrical power [J.M. Andújar, F. Segura, Renew. Sust. Energy Rev. 13, 2309 (2009)], [J. Larminie, A. Dicks, Fuel Cell Systems Explained, 2nd edn. (John Wiley & Sons, 2003)]. As a matter of fact, the voltage generated by a fuel cell strongly depends on both the load power demand and the operating conditions. Besides, as a result of many design aspects, fuel cells are low voltage and high current electric generators. On the contrary, electric loads are commonly designed for small voltage swing and a high V/I ratio in order to minimize Joule losses. Therefore, electric loads supplied by fuel cells are typically fed by means of an intermediate power voltage regulator. The specifications of such a power converter are to be able to step up the input voltage with a high ratio (a ratio of 10 is a classic situation) and also to work with an excellent efficiency (in order to minimize its size, its weight and its losses) [A. Shahin, B. Huang, J.P. Martin, S. Pierfederici, B. Davat, Energy Conv. Manag. 51, 56 (2010)].This paper deals with the design of this essential ancillary device. It intends to bring out the best structure for fulfilling this function. Several dc-dc converters with large voltage step-up ratios are introduced. A topology based on a coupled inductor or tapped inductor is closely studied. A detailed modelling is performed with the purpose of providing designing rules. This model is validated with both simulation and implementation. The experimental prototype is based on the following specifications: the fuel cell output voltage ranges from a 50 V open-voltage to a 25 V rated voltage while the load requires a constant 250 V voltage. The studied coupled inductor converter is compared with a classic boost converter commonly used in this voltage elevating application. Even though the voltage regulator faces severe FC specifications, the measured efficiency reaches 96% at the rated power whereas conventional boost efficiency barely achieves 91.5% in the same operating conditions.

The propagation of radially polarized partially coherent beams in uniaxial crystals orthogonal to the optical axis is investigated. The analytical formulae for the elements of the cross-spectral density matrix of radially polarized partially coherent beams propagating through uniaxial crystals orthogonal to the optical axis are derived. The effect of initial coherence and ratio of extraordinary and ordinary refractive indices on the intensity and effective beam widths is illustrated analytically and numerically. The results show that the propagation properties of radially polarized partially coherent beams in uniaxial crystals orthogonal to the optical axis are closely related to the initial coherence and the ratio of extraordinary and ordinary refractive indices.

The effect of (0.5–3.5) wt.% Ag additions on microstructure, melting, corrosion and mechanical properties of Sn-9Zn eutectic lead-free solder alloy has been studied and analyzed. The study included X-ray diffraction and scanning electron microscopy (SEM) to identify the microstructure of these alloys. The results showed that, continuous additions of Ag caused formation of Ag-Zn and Ag-Sn compounds which led to decrease the precipitations of Zn in Sn-matrix. These compounds led to increase the melting point of the alloys, which confirmed by the formation of small endothermic peaks in the higher temperature range followed the main peak of the DTA curves. Also, the DTA measurements confirmed that the alloy of composition Sn-9Zn-3.5Ag is the ternary eutectic alloy. Vicker's micro-hardness number of Sn-9Zn alloy increases with small additions of 0.5 and 1 wt.% Ag. Furthermore, it decreases to lower values with further increase of Ag content. Also, micro-creep behaviour, creep rate and corrosion behaviour of the Sn-9Zn-Ag alloys have been measured at room temperature.

Laser propulsion in a water environment is influenced by oscillating features of a laser-induced bubble. In our study an optical beam deflection method is used to investigate dynamics of laser-induced semispherical cavitation bubbles near three different interfaces: the rigid boundary (water-solid interface), the free surface (water-air interface) and the liquid-liquid interface (water-soybean oil interface), and in the bulk. The maximum radius of the first bubble oscillation R max1 was widened and the collapse time T 1 is prolonged in the case of the rigid boundary. R max1 is diminished and T 1 is shortened in the case of the free surface and the water-oil interface, among which the latter makes R max1 even smaller. In order to get the maximum propelling force in different distances near different medium interfaces, different pulse energy of the laser is used. The bubble moves toward the rigid boundary and moves away from the free surface during its oscillations. This will change the application point of the propelling force on the object, and cause a change in the propelling direction of the object.

The discrete kinetic model is used to study the propagation ofsound waves in system of hard-disk-like rotating gases. Theanomalous (negative) attenuation or amplification which ispossibly due to the binary collision of a dilute-enough rotatingdisk system (each with opposite-sign rotating direction or angularmomenta but the total (net) angular momenta is zero) ormicroreversibility might arise from the implicit balance of theangular momentum during encounter. Our results might give usefulidea to the instrumentation set-up of possible acceleration ofcosmic rays passing through this kind of channel and direct orinverse cascades in two-dimensional rotating gases ofastrophysical problems.

The band structure of Li2B4O7(100) and Li2B4O7(110) was experimentally determined using a combination of angle-resolved photoemission and angle-resolved inverse photoemission spectroscopies. The experimental band gap depends on crystallographic direction but exceeds 8.8 eV, while the bulk band gap is believed to be in the vicinity of 9.8 eV, in qualitative agreement with expectations. The occupied bulk band structure indicates relatively large values for the hole mass; with the hole mass as significantly larger than that of the electron mass derived from the unoccupied band structure. The Li2B4O7(110) surface is characterized by a very light mass image potential state and a surface state that falls within the band gap of the projected bulk band structure.