Single photon counting, based on single photon sources anddetectors, is a key ingredient for certain applications aiming atnew quantum information technologies. Quantum cryptography, quantumradiometry, distributed quantum computing, as well as adjacenttechnologies such as biomedical and astronomical imaging, and lowpower classical communication also rely on single-photon technology.This paper reviews the present status of single photon sources andrelated counting measurement techniques, based on correlated (orheralded) photons in parametric down-conversion, and their possibleimpact on the above mentioned technologies, as well as an assessmentfor photon standards in the future.

For a uniform distribution we have theoretically studied the subband structure of p-type δ-doped GaAs inserted into a quantum well at T = 0 K. We will investigate the influence of the δ-doping concentration and the layer thickness. The electronic properties such as the depth of confining potential, the density profile, the Fermi level, the subband energies and the subband populations have been calculated by solving the Schrödinger and Poisson equations self consistently. In this study, we have seen that the heavy-hole subbands contain many more energy states than the light-hole ones, the population of the heavy-hole levels represent approximately 91% of all the carriers.

A theoretical study (by using the Nonequilibrium StatisticalOperator Method) is performed on the ultrafast transient transportproperties of photoexcited carriers in ZnSe subjected to electricfields up to 35 kV/cm. The electron and hole drift velocityevolution towards the steady state present maxima in subpicosecondscale.

In this paper we discuss and model the effects of the density of defects in hydrogenated amorphous silicon from an electronics point of view. To this end, we have created a SPICE model that accounts for the two main field effects, Poole-Frenkel and tunnel, responsible for the leakage current. The comparison between our model and the experimental data shows that our approach allows a quick evaluation of the quality of the device with no need to run a complete steady state measurement. Also, we have validated our SPICE photodiode model by implementing it into a three CMOS simple pixel structure.

The complex permittivity of carbon black/epoxy composites containing different amounts of conductive carbon black particles was reported in the frequency range 100 Hz–15 MHz and over the temperature range 23–80 °C. The shape of experimental spectra of these heterogeneous media gives evidence of a typical dielectric relaxation process below the threshold percolation. The temperature dependence of the dielectric response has been analysed below and at near the epoxy glass transition temperature (T g ≅ 80 °C), for various carbon concentrations. Jonscher's phenomenological model has been used for modelling this relaxation process. The activation energy, deduced from Arrhenius equation, is found to be insensitive to the carbon black concentration. This behavior is discussed in term of the interfacial interaction between the carbon particles and the polymer. Besides, the increase of both parts of the complex permittivity with increasing the carbon black concentration and the temperature is compared to the recently proposed Shin's mixture law.

Zinc telluride thin films have been deposited on glass and silicon wafers substrates at room temperature by thermal evaporation technique in a vacuum of 10−5 Torr. The thickness dependence of both the dc electrical resistivity and thermoelectric power of ZnTe were carried out at room temperature and after being annealed over a thickness range from 22 nm to 170 nm. The type of conduction, the carriers concentration and the conduction mechanisms were revealed. The average thermal activation energy ΔE equals to 0.324 eV for the as deposited films and 0.306 eV for annealed films, it is found to correspond with the ionization energy reported for intrinsic defect levels in ZnTe. Seebeck coefficient measurements showed that ZnTe thin films behave as p-type semiconductor and the average value of the free charge carrier concentration is found to be 1.6 × 1019 cm−3.The built-in voltage, the widt of the depletion region, the diode quality factor and the operating conduction mechanisms have been determined from dark current-voltage (I − V) and capacitance-voltage (C − V) characteristics of p-ZnTe/ n-Si heterojunctions.

Orthorhombic tungsten bronze Pb $_{1-x}$ K $_{2x-3y}$ Smy Nb2O6 (where x = 0.29 and y = 0.145) ceramic has been synthesized by the conventional sintering technique. Preliminary X-ray diffractogram analysis of crystal structure showed that a single phase compound has been formed with orthorhombic system. Frequency and temperature dependences of impedance, modulus, conductivity and dielectric permittivity have been performed in the frequency and temperature range 45 Hz–5 MHz and 35–595 °C respectively. Impedance spectroscopy study showed the presence of both bulk and grain boundary effects in the materials. The complex impedance spectra above 440 °C have been fitted by the superposition of two Cole-Cole types of relaxations. The ac conductivity spectrum obeyed the Jonscher's power law. Modulus analysis indicated the possibility of hopping mechanism for electrical process in the system.

Multiwalled carbon nanotubes (MWCNTs) were synthesised by chemical vapour deposition (CVD) in a C2H6+H2 atmosphere over 20%Fe/SiO2 catalysts. The influence of synthesis temperature, flow-rate and flow ratio of the reactant gases, the amount of catalyst employed and the catalyst reduction temperature on the abundance and crystalline perfection of product was analysed by scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The changes in yield and crystalline perfection, as monitored by Raman G' band relative intensity, were correlated with the variations of synthesis temperature, the diverse catalyst surface area and H2/C supply ratio attained by varying growth conditions. In the range examined, the lowering of catalyst reduction-temperature turns out to be beneficial for both yield and crystalline perfection of the MWCNTs. All the other growth parameters produce opposite effects so the best compromise has to be sought.

Based on numerical simulation technology, the influence of arc currents and axial magnetic fields (AMFs) strength on high current vacuum arc (HCVA) characteristics is studied and analyzed. Simulation results show that electron temperature, ion number density, axial current density, plasma potential, plasma pressure and heat flux density to anode in HCVA are all increased with the increase of arc currents. For very high current vacuum arc, current constriction near cathode side can be more significant than that of anode side. The increase of AMF strength can decrease the above parameters, and will control HCVA more efficiently. The simulation results of HCVA under different arc currents are also verified by experiments.

This paper concerns the study of contact opening under DC voltage in the case of high intensity currents (a few hundred amperes). The application fields are mainly automotive and aeronautical systems. An experimental device has been designed in order to study the opening of contacts under various conditions. The influence of several parameters on contact opening is studied. These are the following: the opening velocity, the current intensity through the closed contact, the nature of the contact materials (Ag, AgSnO $_{2...})$ , the value of the inductance in the electrical circuit... The measured parameters characterizing the opening phase are: the arc duration, the value of the electrode gap when the arc extinguishes, the arc energy.