Over the last two decades, advances in fabrication have led to significant progress in creating patterned heterostructures that support either carriers, such as electrons or holes, with specific band structure or electromagnetic waves with a given mode structure and dispersion. In this article, we review the properties of light in coupled optical waveguides that support specific energy spectra, with or without the effects of disorder, that are well-described by a Hermitian tight-binding model. We show that with a judicious choice of the initial wave packet, this system displays the characteristics of a quantum particle, including transverse photonic transport and localization, and that of a classical particle. We extend the analysis to non-Hermitian, parity and time-reversal (PT$ \mathcal{PT}$) symmetric Hamiltonians which physically represent waveguide arrays with spatially separated, balanced absorption or amplification. We show that coupled waveguides are an ideal candidate to simulate PT$ \mathcal{PT}$-symmetric Hamiltonians and the transition from a purely real energy spectrum to a spectrum with complex conjugate eigenvalues that occurs in them.

Potential sterilization/disinfection of medical devices (MDs) is investigated using a specific plasma process developed at the Université de Montréal over the last decade. The inactivating medium of the microorganisms is the flowing afterglow of a reduced-pressure N2-O2 discharge, which provides, as the main biocidal agent, photons over a broad ultraviolet (UV) wavelength range. The flowing afterglow is considered less damaging to MDs than the discharge itself. Working at gas pressures in the 400—700 Pa range (a few torr) ensures, through species diffusion, the uniform filling of large volume chambers with the species outflowing from the discharge, possibly allowing batch processing within them. As a rule, bacterial endospores are used as bio-indicators (BI) to validate sterilization processes. Under the present operating conditions, Bacillus atrophaeus is found to be the most resistant one and is therefore utilized as BI. The current paper reviews the main experimental results concerning the operation and characterization of this sterilizer/disinfector, updating and completing some of our previously published papers. It uses modeling results as guidelines, which are particularly useful when the corresponding experimental data are not (yet) available, hopefully leading to more insight into this plasma afterglow system. The species flowing out of the N2-O2 discharge can be divided into two groups, depending on the time elapsed after they left the discharge zone as they move toward the chamber, namely the early afterglow and the late afterglow. The early flowing afterglow from a pure N2 discharge (also called pink afterglow) is known to be comprised of N2+ and N4+ ions. In the present N2-O2 mixture discharge, NO+ ions are additionally generated, with a lifetime that extends over a longer period than that of the nitrogen molecular ions. We shall suppose that the disappearance of the NO+ ions marks the end of the early afterglow regime, thereby stressing our intent to work in an ion-free process chamber to minimize damage to MDs. Therefore, operating conditions should be set such that the sterilizer/disinfector chamber is predominantly filled by N and O atoms, possibly together with long-lived metastable-state O2(1 Δg) (singlet-delta) molecules. Various aspects related to the observed survival curves are examined: the actual existence of two “phases” in the inactivation rate, the notion of UV irradiation dose (fluence) and its implications, the UV photon best wavelength range in terms of inactivation efficiency, the influence of substrate temperature and the reduction of UV intensity through surface recombination of N and O atoms on the object/packaging being processed. To preserve their on-shelf sterility, MDs are sealed/wrapped in packaging material. Porous packaging materials utilized in conventional sterilization systems (where MDs are packaged before being subjected to sterilization) were tested and found inadequate for the N2-O2 afterglow system in contrast to a (non-porous) polyolefin polymer. Because the latter is non-porous, its corresponding pouch must be kept unsealed until the end of the process. Even though it is unsealed, but because the opening is very small the O2(1Δg) metastable-state molecules are expected to be strongly quenched by the pouch material as they try to enter it and, as a result, only N and O atoms, together with UV photons, are significantly present within it. Therefore, by examining a given process under pouch and no-pouch conditions, it is possible to determine what are the inactivating agents operating: (i) when packaged, these are predominantly UV photons, (ii) when unpackaged, O2(1Δg) molecules together with UV photons can be acting, (iii) comparing the inactivation efficiency under both packaged and unpackaged conditions allows the determination of the relative contribution of UV photons (if any) and O2(1Δg) metastable-state molecules. Such a method is applied to pyrogenic molecules and to the enzymatic activity of lysozyme proteins once exposed to the N2-O2 flowing afterglow. Finally, the activity of the infectious prion protein is shown to be reduced when exposed to the present flowing afterglow, as demonstrated by both in vitro and in vivo experiments.

Single crystals of MoSe2−xTex (x = 0.25, 0.5, 1, 1.5, 1.75) were grown by chemical vapor transport technique. The stoichiometric composition of grown crystals was confirmed by energy dispersive X-ray spectroscopy. Transport properties like electrical resistivity, Seebeck co-efficient measurements at high temperature and Hall effect at room temperature were studied on these samples. The obtained results are discussed in details in this paper.

We compared the performances of polymer-based photovoltaic devices prepared from different formulations of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS). The PEDOT:PSS buffer layer is incorporated between the indium tin oxide (ITO) electrode and the active layer, which is composed of a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). A highest efficiency of 3.86% (under AM1.5 solar illumination) was achieved for device prepared from a PEDOT:PSS trade-named high conductivity grade. However, annealing devices at a temperature over 120 °C results in decreased photovoltaic performance. This study shows that attention has to be paid to chemicals used to formulate high conductive PEDOT:PSS to become compatible with the production of solar cells involving thermal processing.

In this paper we propose a new silicon nanowire photodetector model based on a single-electron transistor for single charge detection (photo-NWSET). In the first part of this work we present the two blocks of the device structure (reading and detection blocks). The presented model is consisting of two blocks capacitively coupled. The first SET (SET1) is supposed to read the charge whereas the detection block is represented by the nanowire (NW) system associated to an optical source. We modeled the NW by a series of seven islands separated by eight tunnel junctions (8TJs). In the second part of this work, we investigate the effects of photoexcitation on Id-Vg curves and we present results obtained on the output (photo-NWSET) characteristics after variation of power illumination and response time.

In this work, electric properties of two matrices based on nematic epoxy monomers with azoxy groups are compared. The process of curing the monomers with DDM amine was monitored by means of dielectric spectroscopy at temperatures of 110 °C and 120 °C. In the next step, measurements of direct current conductivity were performed for the epoxy matrices cured at the temperature of 120 °C. The conductivity in the studied matrices was of the order of 10−9–10−7 S/m at temperatures between 150 °C and 170 °C. The conductivity of both the samples was of activation nature and their resistance grew rapidly below the temperature of 140 °C. Dielectric studies were also carried out for both the materials in a broad range of frequency and temperature. A relaxation process with similar activation energy was observed in both the cases. This process can be connected with the motion of polar azoxy groups present in the mesogen. An additional relaxation process appeared at higher temperatures in one of the cases, it was probably related to some structural change in the material.

The characteristic properties, the critical surface transverse field Ωsc and the Curie temperature Tc, for an N-layer ferroelectric thin film with epitaxy surface layers Ns described by the transverse field Ising model have been studied by the differential operator technique within the framework of effective-field theory with correlations. The analytical equation for the phase diagrams of ferroelectric thin films is derived. The surface transverse field Ωs dependence of the Curie temperature Tc in the ferroelectric thin film with different epitaxy surface layers is calculated. Meanwhile the epitaxy surface layer number Ns dependence of the critical surface transverse field Ωsc and the Curie temperature Tc is also examined. The results show that the critical properties depend heavily on modifications of interchange interactions and transverse fields in the epitaxy surface layer.

Bilayer hybrid solar cells were prepared by solution deposition of CdS thin films on conductive glass substrates (ITO), followed by spin-coating or drop-casting poly (3-hexylthiophene) (P3HT) solution on a CdS surface. After a slow drying process, the P3HT films of different thicknesses (from 100 to 725 nm) were annealed at temperatures (T1) from 110 to 190 °C, called pre-metal contact annealing. Then carbon paint was collocated on top of P3HT and gold was evaporated. The whole structure was annealed for the second time, called post-metal contact annealing, at temperature (T2) between 110 and 190 °C. The continuous increase of the (1 0 0) crystalline plane and the optical absorption coefficient of P3HT films with annealing temperatures indicates the improvement of molecular order inside the polymer films induced by the thermal annealing process. The better ordered P3HT films lead to lower series resistance and higher fill factor in the corresponding solar cells, suggesting the enlargement of charge carrier mobility in annealed P3HT films. On the other hand, the photovoltaic performance is also affected by T2 temperature; a low T2 improves the ohmic contact between P3HT and the metal contact to benefit the charge carrier extraction, whereas a high T2 may deteriorate that union. The same observation was obtained in CdS/P3HT solar cells with P3HT films of different thicknesses. The best energy conversion efficiency of 0.44% was obtained in CdS/P3HT cells with 305 nm thick P3HT annealed at T1 = 190 °C and T2 = 110 °C for 10 min each.

We have studied the structural, morphological and optical properties of In2S3 layers deposited on glass substrate by the spray pyrolysis method with the molar ratio S/In varies from 1 to 4. The substrate temperature was maintained at 613 K. The characteristics of these films have been determined by X-ray diffraction (XRD), optical absorption-transmission and atomic force microscopy (AFM). Their structure is strongly dependent on the molar ratio. The deposit is mainly constituted by the β phase towards (4 0 0) direction. No characteristic peaks were observed for other impurities such as In2O3, S or In2(OH)3. The best crystallinity and surface morphology are obtained at molar ratio equal to 2.5. At this ratio, the crystallites coalesce and the local roughness is of the order of 1 nm. Optical transmission of 80% has been achieved in the visible spectrum. In2S3 band gap energy reached 2.63 eV from layers with x = 2 and deposited at Ts = 613 K.

The crystallization of amorphous silicon thin films by electron beam exposure was studied. Amorphous silicon and silicon dioxide layers were deposited on glass substrate by PECVD at 360 °C. The optimization to crystallize 300 nm thick amorphous silicon film was carried out at a RF power of 300 W, DC voltage of 1500 V, Argon gas flow rate of 3 sccm and a distance between electron beam mesh and sample of 40 mm. High quality nano-crystalline silicon films with an activation energy of 0.47 eV from conductivity, a grain size of 15–45 nm from SEM and Raman crystalline volume fraction of 93.1% were fabricated. We expect that e-beam exposure will be applied to crystallization of amorphous silicon films.

In the present work the optical properties of Ge15Se60X25 (X = As or Sn) films have been studied. Optical reflectance and transmittance of films were obtained at normal incident in the wavelength range (500–2500 nm). The transmittance measurements were used to calculate the refractive index n and the absorption index k depending on Swanepole’s method. The analysis of the optical absorption data revealed that the optical band gap Egopt was allowed indirect transitions. The optical constants such as complex dielectric constant, dispersion parameters (E0 and Ed), ε∞, VELF, SELF and dissipation factor tan δ were determined. It was found that Egopt and the oscillator energy E0 decreased with As addition than Sn addition. Whereas, the Urbach tail energy Ee, the dispersion energy Ed, the real and imaginary dielectric constants ε1 and ε1, the high frequency dielectric constant ε∞ and the dissipation factor tan δ increased with As addition than Sn addition.

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.

This paper exploits an energetic initiator realized by integrating Al/Ni multilayer nanofilms with semiconductor bridge (SCB). The as-deposited nanofilms have been characterized with varied analytical techniques. Results show that distinct nanofilms are sputter deposited in a layered geometry and give a heat of reaction equal to 1134 J/g. The firing tests of the initiators were accomplished using capacitor discharge unit. Results show that the initiators possess several excellent characteristics such as fast ignition time, low power consumption, high output energy and so on. Therefore, Al/Ni multilayer nanofilms are suitable heat source for improving the reliability of SCB initiators.

Series of CoxCr1−x thin films have been evaporated under vacuum onto monocrystalline silicon substrate, x being atomic percent of cobalt. The thickness ranges from 17 to 220 nm, values measured by Rutherford backscattering spectrometry. The samples have been annealed under vacuum for one hour at 700 °C. The as deposited films show a hexagonal close packed (hcp) structure while the annealed films show both hexagonal close packed and face centered cubic (fcc) structures. While the as deposited films are under a compressive stress, the annealed films, on the contrary, are under a tensile stress. The hysteresis loops present the same features for the as deposited and annealed films concerning the in-plane and out-of-plane anisotropies. Nevertheless, the coercive field is strongly improved for the annealed films. Moreover, these latter films present very high values of the squareness. A squareness value up to 0.96 has been measured. All these results and others are analyzed and discussed.

Combining with the self-consistent condition and extended 5 × 5 matrix, we theoretically analyzed the polarization properties of the eigenmodes throughout the nonplanar ring resonators with different structures. According to the satisfactory cross section size of the eigenmodes, a comparative study of the stability properties of these nonplanar ring resonators is also provided, and the three dimensions stability space of these resonators are presented for the first time as far as our knowledge goes. The results show that the major and minor axes of the cross section change with the propagation distance and have a symmetrical point for resonators with two different structures, and the area of the stable region for these resonators can be extended by changing the incident angles of the laser beam or the radii of mirror surfaces in the resonator. These interesting results are important for designing and arranging the diaphragm in ring resonators with a nonplanar structure, as well as optimizing the structure of the resonators themselves.

It is well known that the interactions between a coherent light and a scattering medium produce a speckle pattern. But, even if intensity and phase statistics have been already well described for a long time, the statistics of the increments of the phase spectrum have never been explored. In this paper, we firstly introduce these concepts before demonstrate that phase spectrum increments contain informations on the medium observed. Moreover, we show that phase spectrum increments allow reaching informations on the media which are not present in the classical approaches based on the intensity. Monte Carlo simulations are used to this aim.

For imaging and manipulation of biological specimens application of atomic force microscopy (AFM) in liquid is necessary. In this paper, tapping-mode AFM cantilever dynamics in liquid close to sample surface is modeled and simulated by well defining the contact forces. The effect of cantilever tilting angle has been accounted carefully. Contact forces have some differences in liquid in comparison to air or vacuum in magnitude or formulation. Hydrodynamic forces are also applied on the cantilever due to the motion in liquid. A continuous beam model is used with its first mode and forward-time simulation method for simulation of its hybrid dynamics and the frequency response and amplitude versus separation diagrams are extracted. The simulation results show a good agreement with experimental results. The resonance frequency in liquid is so small in comparison to air due to additional mass and also additional damping due to the viscosity of the liquid around. The results show that the effect of separation on free vibration amplitude is great. Its effect on resonance frequency is considerable too.

Nanosilver solution, prepared by anodic dissolution with high DC voltage in doubly distilled water, is free of undesirable chemicals and forms a highly pure product which is suitable for different applications, especially in the medical and pharmaceutical fields. In this study high DC voltage electrolysis was implemented to form nanosilver solutions with varying electrode diameters, anode-cathode distances, and electrolysis duration. The process was monitored while the cell was in operation, and the characteristics of the resulting solution were analysed afterwards. Cell reactions included: colour changes in the solution bulk due to the reduction of silver ions forming nanoparticles, anodic dissolution of silver, intense gas evolution at both electrodes, and chemical reactions in the solution causing nanosilver formation. UV-Vis characteristics, particle size distribution, transmission electron microscopy (TEM) images, solution concentrations, conductivities, and ζ-potentials were all found to depend on the electrode’s distances, temperature, electrolysis duration, and current density. Nanosilver preparation can thus be considered a combination of electrochemical reactions (such as silver dissolution at anode and water decomposition to generate hydrogen and oxygen), and chemical reactions between the electrolytic products from the solution bulk.

This paper deals with the development of a new generation of electric motors (7.5–15 kW) for automotive powertrains. The target is a full electric direct drive vehicle, for the particular application to heavy quadricycles. An original axial flux PM structure is proposed due to the simplicity of its manufacturing. However it leads to a 3D structure, difficult to study. The paper deals with analytical models that can be used to achieve the analysis and the sizing of the motor. The electromagnetic behavior is modeled using a simple magnetic equivalent network and the thermal behavior is analyzed with a thermal network. Finally, the analytical results are compared to those experimentally obtained and it proves the interest of the proposed structure: the construction is simple and the performances are satisfying.