This paper shows that accurately optimised asymmetric three phase-shift (3PS)-distributed feedback (DFB) laser structures can strongly improve the stability of the single-longitudinal mode (SLM) operation, described by the mode selectivity and the flatness of the photon density profile, through an extended range of current injection, when compared to optimised symmetric 3PS-DFB structures reported elsewhere. This study reveals its importance in modern high bit-rate optical communication systems, by enhancing the possibility of attaining high performance DFB lasers, in easily fabricated structures. The procedure, based on matrix techniques, aims at the description of the optimal design of the laser structure and it is described step-by-step. Above-threshold calculations have been accomplished to evaluate the performance of the optimised asymmetric 3PS-DFB structure, namely: the mode selectivity ($G$), the flatness, the lasing wavelength, the optical power, and the side-mode suppression ratio (SMSR) evolutions with the current injection. For a current injection five times bigger than the threshold current, substantially improvements in $G$ (five times bigger) and in the SMSR (about 9 dB higher) are achieved when compared to similar, but symmetric, DFB structures.

This article is a comprehensive review of the subject of near-field nano imaging and spectroscopy by surface plasmon polaritons induced on a metallized probe. The emphasis of the review is on fundamental aspects of plasmon enhancement and near-field spectroscopy, which are categorized as optical antenna structures, polarization properties in near-field, resonance frequency of surface plasmons, etc. Most recent studies that contribute to the understanding and interpretation of these phenomena are highlighted. Applications of near-field optics as newly established analytical tools for biology, materials sciences and plasmonic superlenses are included in the article.

In this paper, we present a model proposition of photo-SET (single electron photo-detector) aiming at detecting one by one electrons. In the first part of this work, we present the two blocs of the proposed photo-SET (reading and detection blocs). The device structure presented is consisting of two SETs capacitively coupled. In this model, the first SET (SET1) is supposed to read the charge whereas the detection bloc is represented by the second SET (SET2). In the second part, we investigate the effects of photoexcitation on Id-Vg curves and we present results obtained on the output photo-SET characteristics after variation of power illumination and response time.

Earlier we reported that the pits generated in CR-39 detectors during Pd/D co-deposition experiments are consistent with those observed for pits that are of a nuclear origin. Spacer experiments and track modeling have been done to characterize the properties of the particles that generated the tracks in the CR-39 detectors. The effect of water on the energetics of the particles and their resultant tracks is discussed.

It is well known that the implementation of flexible organic electronic devices (FEDs) in our everyday life improve and revolutionize several aspects of our behavior. Although there has been considerable progress in the area of flexible inorganic devices (based on Si), there are numerous advances in the organic (semiconducting, conducting and insulating), inorganic and hybrid (organic-inorganic) materials that exhibit customized properties and stability, and in the synthesis and preparation methods, which are characterized by a significant amount of multidisciplinary efforts. The understanding of the organic material properties can lead to the fast progress of the functionality and performance of flexible organic electronic devices. An crucial ingredient for this is the strong interdisciplinary nature of the area of organic electronics, which brings together experts in chemistry, physics, and engineering, removing the traditional boundaries between the individual disciplines. Therefore, the understanding of the properties of organic insulators, semiconductors, and conductors as well as the effect of their synthesis process, microstructure and morphology is the goal of the current research efforts. In this work, we summarize on the latest advances in the fields of organic (semi-) conducting materials and hybrid barrier layers to be used as active layers and for the encapsulation of the materials components for the production of FEDs (such as flexible organic light-emitting diodes, and organic solar cells).

In this study, new possibilities for higher efficiency poly-Si thin film solar cells are investigated using MEDICITM device simulator. The poly-Si p+-n-n+ thin film solar cell with a thin a-Si p+ layer is found to have higher efficiency than the homojunction p+-n-n+ cell. Further improvement in efficiency of the heterojunction p+-n-n+ cell is achieved by introducing a thin μc-Si layer at the interface of a-Si emitter and poly-Si absorber layers. The μc-Si layer at the interface is found to reduce the recombination losses at the interface and improved the fill factor and efficiency of the cell. The photovoltaic parameters of the cell and the absorber layer thickness for optimum efficiency are highly influenced by grain size and passivation at the grain boundary.

Saccharomyces Cerevisiae (S. Cerevisiae) and Mrakia Frigida (M. Frigida) were deactivated using alternative current dielectric barrier discharge (DBD). The deactivation was done in argon and oxygen plasma under different discharge currents. It has been found that ozone and atomic oxygen play a significant role in the deactivation of S. Cerevisiae and M. Frigida when using DBD discharge, while argon ions are less important in the deactivation of the same microorganisms in argon DBD.

A hybrid process compatible with reel-to-reel manufacturing is developed for ultra low-cost large-scale manufacture of disposable microfluidic chips. It combines ultra-short laser microstructuring and lamination technology. Microchannels in polyester foils were formed using focused, high-intensity femtosecond laser pulses. Lamination using a commercial SU8-epoxy resist layer was used to seal the microchannel layer and cover foil. This hybrid process also enables heterogeneous material structuration and integration.

The microstructure of thin deposits of poly(3-hexylthiophene) on silicon surfaces is investigated as a function of the solution concentration, the maturation time and the solvent nature, with the aim of generating one monolayer of P3HT nanofibers on the surface. These films are then exposed to a NOPF6 solution, in order to oxidize the conjugated system and to produce conducting nanostructures. The effect of the chemical doping on the microscopic morphology and the electrical properties is analyzed on the basis of AFM and I-V measurements.

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.

Current voltage and capacitance-voltage characteristics for SnPc thin film with ~105 nm thickness; deposited on p-GaAs single crystals have been investigated. The dark current voltage-characteristics of the prepared junction have been investigated in a temperature range from ~303 to 393 K. The obtained results showed rectification behaviour. At low forward and reverse bias, the current was found to be limited by the thermoionic emission, while at high forward voltage, space charge limited current dominated by a single trap level of 0.22 eV. The analysis of the dark capacitance voltage characteristics indicated that the carrier concentration is 1.4×1014 cm-3 with a built in voltage ~0.55 eV.

This paper discusses homogenization formulas and mixing rules that connect effective dielectric properties of mixtures with their microstucture. The special point of view in this paper is that all parameters appearing in mixing formulas are treated with equal status. The parameters that can be varied are the permittivities (which are allowed to be negative as well as positive) of the inclusion, environment, and composite, the volume fraction, spatial dimension, and an abstract parameter which chooses the given mixing formula type. The analysis helps in the interpretation of predictions from classical mixing rules when they are extended into the domain of negative-permittivity metamaterials.

Non-destructive method of spectroscopic ellipsometry (SE) from IR to FUV was applied to study PEDOT/PSS thin films deposited by spin coating from aqueous dispersions of the material with different N,N-Dimethylformamide (DMF) volume percent. In our work we used the Tauc-Lorentz model to describe the dielectric function of PEDOT/PSS:DMF films in the Vis-FUV energy region. First, the spectrum analysis showed that the thickness and the fundamental band gap Eg of the film is being decreased with the increase of DMF content in the dispersion. Taking into account that the heating temperature is below the boiling point of DMF we assume that DMF molecules are incorporated in the film volume and act as dopants. Further more, this means that carrier concentration is being increased and thus we have higher electrical conductivity. The existence of DMF molecules in the film proved from FTIR SE, which can probe the bonding structure of the materials. The results showed lowering of peak intensity assigned to PEDOT/PSS and appearing of peaks assigned to DMF in the imaginary part of spectrum. In conclusion, SE is a potential tool for the evaluation of electronic properties for conductive polymers.

The precise control of organic thin film processing by organic vapor phase deposition (OVPD®) is presented and analyzed on device level. OVPD® offers accurate and individual control of deposition layer properties like mixing of several materials (co-deposition) and the control of various morphologies by a wide process parameter space given by, e.g. substrate temperature, deposition rate and pressure. The benefit of precise co-deposition is demonstrated by an OLED with a sensitive twofold-doped emissive layer and revealed a doping level of 0.26% for the red dopant with a std. dev. of 0.38%. The effect of the various morphologies is investigated by optimizing the efficiency of molecular organic solar cells consisting of copper phthalocyanine (CuPc) and C60. With defined process parameters efficiencies of up to 3.0% were demonstrated.

We propose a theoretical study of optimization of metal-dielectric multilayer in order to approach -1 effective refractive index for transverse magnetic waves and a wavelength in the visible. The absorption losses of metal appear to be a crucial factor that affects the effective properties of the multilayer. Taking advantage of the dispersion relation of Bloch modes, we show that the losses not only decrease the transmission of the stack, but also change the negatively refracted angle. Then, we propose that using a gain-providing semiconductor (GaN) may allow compensating for the losses in metal layers. In theory, the performances of the structure can be improved greatly when gain is involved. When considering finite thickness structures, and with appropriate thickness for the terminating layers, it is possible to obtain a high transmission of the structure. A near -1 effective index metal-dielectric stack with high transmission may pave the way to the realization of negative quasi-isotropic refraction in the visible or ultraviolet wavelength range.

The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of metal-organic compound conductive polymer-semiconductor Al/P2ClAn(C2H5COOH)/p-Si structures were measured in the temperature range 80–340 K. P2ClAn: the poly(2-chloroaniline). The P2ClAn emeraldine salt was synthesized chemically by using propionic (C2H5COOH) acid. The analysis of I-V characteristics based on the thermoionic emission (TE) mechanism has revealed a decrease of zero-bias barrier height and a increase of the ideality factor at lower temperatures. Temperature dependence of the barrier height (BH) has shown a disagreement with those calculated from C-V characteristics. This behaviour is attributed to Schottky barrier inhomogeneities at interface. The temperature coefficient of BH has been found to be -2.9×10-4 eV/K for Al/P2ClAn(C2H5COOH)/p-Si. ln(I0/$T^{2})$ versus 1/T plot gives activation energy and Richardson constant $A^{\ast}$ as 0.12 eV and 3.82×10-9 A/K2 cm2, respectively.

In this work we present a fabrication method for developing thermal sensors on flexible organic substrates. The constructed devices consist of Pt resistors which are directly integrated to the copper tracks of a flexible copper-clad laminate. They reside on top of a 12 $\mu $m thick SU-8 planarization layer, while a sacrificial layer utilized by the negative photoresist ma-N was used in order to define the resistor pattern. The resistors can act as both heating and temperature sensing elements, while due to small thickness and the low thermal conductivity of the Kapton substrate, a very effective thermal isolation is achieved. The minimum radius of curvature of the fabricated devices was found to be 5 mm. As the device is in direct communication to the macrowolrd, the need for wire bonding is eliminated, while the final surface of the produced sensor is relatively planar. The overall process is simple and cost-effective with minimal requirements in fabrication time. The potential application field of the presented devices is considered quite extensive as they can be directly expanded into flexible sensors able to measure quantities such as fluid flow rate, displacement or vacuum.

The structural investigations of model organic systems like pentacene on silicon oxide in the monolayer regime is very important for the basic understanding of initial nucleation process together with the electronic performance of transistor devices. A method for the evaluation of the island formation and layer closing of the first monolayer is introduced. The method is based on specular X-ray reflectivity and diffuse scattering and reveal integral information on the coverage together with the size and separation of pentacene islands. The results are in good agreement with AFM investigation that encourages the use of this type of investigation in in-situ experiments.