In this paper, based on diffusion and thermionic-field emission conduction mechanisms in crystalline-insulator-crystalline system, a comprehensive model of current conduction for polycrystalline silicon is developed, considering the doping effect and the temperature effect on carrier mobility. The simulation results show a good agreement with the experimental data without unphysical fitting parameter. It is demonstrated that the effective diffusion velocity limits the carrier movement at light doping level, while the thermal velocity and the tunneling effect dominate the carrier conduction at heavy doping concentration. The developed model can interpret the conduction characteristics of polysilicon thin films over a wide range of doping levels with temperature.

The organic thin-film transistors (OTFTs) incorporating pentacene/SU-8 interface were fabricated and characterized. SU-8, a reliable epoxy-based photoresist, is tested as a potential highly-stable polymeric gate dielectric for OTFTs. The fabricated devices showed promising electrical performance with on-off ratio up to 107 and field-effect mobility up to 0.56 cm2/V s. Several device characteristics are further analyzed. There existed a leakage current path due to the uncontrolled pentacene coverage and we revealed that precise alignment of the evaporation mask of pentacene is critical for eliminating this problem. Pentacene grain formation largely depended on the growth condition on the SU-8 surface and small-grain films offered outstanding performance possibly owing to enhanced inter-domain connections. Natural degradation of the OTFTs is also discussed in terms of environmental stability and the pentacene/SU-8 transistor operated with noticeable air stability under ambient conditions.

K1−xNaxHC4H4O6 · H2O (x = 0.3 and 0.7) single crystals have been grown by the gel encapsulation technique. The composition-related structural, optical and electrical properties are investigated. All the crystals have an orthorhombic structure. With the increase of Na content, the transparency of the crystals increases and the band gap values decrease. Good optical transmission of these crystals predicts them to be potential candidates for nonlinear optical applications. From the study on electrical conductivity, a semiconducting behavior is observed for these crystals. Resistivity, activation energy and hoping range are found to decrease with Na doping. DC conductivity behavior observed in these crystals is found to follow a variable-range hopping model. A clear indication of disorder induced in these crystals after Na doping is observed.

Nanocomposite TiO2-ZnO thin films, with different ZnO content, were deposited by electron-beam evaporation on glass and Si(1 0 0) substrates. The resulting films were annealed in air for 1 h at 450 °C. X-ray diffraction revealed the presence of monoclinic β-TiO2 and hexagonal ZnO for the films prepared with ZnO content of 0 at.% and 100 at.%, respectively. Mixed monoclinic β-TiO2 and hexagonal ZnO phases were observed at higher ZnO content between 50 at.% and 85 at.%. Spectroscopic ellipsometry (SE) was employed to determine the film thickness and optical constants. A two-layer model was used to describe the experimental ellipsometric data. At any wavelength longer than 390 nm, the refractive index decreases gradually with increasing ZnO content in the composite films. The optical band gap increased with increasing ZnO content. The photocatalytic behavior of TiO2-ZnO thin films was mainly evaluated by measuring the decomposition of methylene blue. The nanocomposite film with ZnO content of 8 at.% has the best photocatalytic activities.

The dielectric dispersion of copolymer ferroelectric Langmuir-Blodgett thin film has been subjected to investigation using multiple-arc methodology with the associated relaxation time distribution. The analysis made use of reported data over the frequency range 10 Hz–2 MHz and over the temperature range of 308–398 K. The analysis indicated the presence of two distinct polarization modes corresponding to high- and low-frequency arcs. The modes have different characterizations in terms of the relaxation spread and mean time trends with temperature. The trends of the low-frequency arc with temperature support ferroelectric property for the thin L-B film. Satisfactory agreements have been realized between the experimental data and those derived by multiple-arc approach.

TiO2 nanorods, TiO2 nanorod/TiO2 nanoparticle and TiO2 nanorod/ZnO nanoparticle composite structures were integrated as photoanodes in backside illuminated dye-sensitized solar cells (DSSCs). Incorporation of TiO2 nanoparticles into the bare nanorods increased the dye loading and improved the short-circuit current density (Jsc) from 2.22 mA/cm2 to 3.57 mA/cm2. ZnO nanoparticles electrochemically grown into the TiO2 nanorod layer could increase the surface area. Nevertheless, this considerably reduced the Jsc to 0.57 mA/cm2 and consequently cell efficiency. Electrochemical impedance spectroscopy (EIS) results showed that ZnO incorporated samples have better effective diffusion coefficient of electrons in comparison with bare TiO2 nanorods while the recombination rate of injected electrons to photoanode with electrolyte is near eight times faster than bare TiO2 nanorods. ZnO incorporated samples showed lower electron density at steady state in the conduction band also. The worse performance of ZnO incorporated samples was attributed to lower electron injection efficiency from excited dye molecules. Monitoring electron transport properties of the cells measured by EIS pointed out the crucial role of electronic structure of composite film components on the performance of cells. Our results showed that EIS technique could be used as an efficient characterization method for precise monitoring of charge transport in nanocomposite photoanodes for DSSCs.

The porosity type in spark plasma sintered alumina was studied by variable energy positron beam technique. The gamma ray energy spectra of interest in the region of the annihilation peak were analyzed by means of Compton-to-peak ratio and deconvolution into Gaussians of the Doppler broadened annihilation peak. The contributions of the two narrow Gaussians (centered and red-shifted) revealed difference in the porosity type according to the heating rate. The samples sintered at low heating rate showed open porosity. Closed porosity appeared at 1050 °C as a result of formation of isolated pores. For the samples sintered at high heating rate, closed porosity was found to be significant even at comparatively low sintering temperatures which was explained by a blocking effect at the sample free surface.

Acoustic external cloak is an important device, which can cloak an object without encircling it but allows the object to exchange information with the outer region. By choosing appropriate spatial transformation, we design a cylindrical acoustic external cloak with only spatially varying bulk modulus in this paper. The general expressions of material parameters are derived, and then the performance of the external cloak is simulated based on full-wave simulations. The advantage of the cloak is that mass density elements are constants, and only bulk modulus is a function of radius, which make it easier to realize in practice. Besides, the effects of perturbations of parameters on the performance of the cloak are also investigated. This work provides a feasible way for the fabrication of the metamaterial-assisted acoustic external cloak.

The transmission properties of a resonator based on one air layer sandwiched by two-layered anisotropic metamaterials with different negative-permittivity tensors are studied through analytical analysis and numerical calculations. The resonator has orthogonally polarized dual wavelength output. The difference of the two wavelengths can be adjusted through changing the permittivity tensors, and the ratio of the intensities of the two orthogonally polarized waves can also be adjusted through changing the polarization direction of incident wave. The study results may find applications in the design of laser resonator.

The efficiency of acousto-optic interaction in single-mode strip silica waveguide is analyzed theoretically by determining the overlap integral between the optical and acoustic field distributions. The results show that there is a good overlap of the optical and SAW fields in the low SAW frequency range. At high acoustic frequencies, the overlap integral decreases with increasing acoustic frequency. At 216 MHz, the maximum of 0.8544 for the overlap integral is obtained, provided the H/Λ equals 0.02. At last, the diffraction efficiencies for acoustic frequency of 216 MHz are calculated as a function of the square root of acoustic power for different acoustic apertures.

We investigate the vibration properties of adsorbed nanostructure on the infinite square crystalline surface. The surface is considered as an infinite slab of one atomic layer, and the nanostructure as an isolated diatomic molecule chain on the surface of a cubic lattice which is parallel to y-axis, and takes three different positions: top, hollow and bridge. The vibrational dynamics of the structure is considered within the harmonic approximation framework. The evanescent and propagating vibrational field of the perfect lattice is determined and discussed. The presence of the molecule chain breaks down the translation symmetry in one direction and gives rise to localized states on its neighborhood. The mathematical framework of the matching method is used to analyze the localization phenomena at the nanostructure boundaries. Typical dispersion curves for modes of energies along the inhomogeneity are given with their polarizations. The fine structure of the spectrum and its origins are clearly identifiable, which gives a new insight into the localization problem. Furthermore, the existence and nature of the localized phonons like modes associated with an isolated defect are derived, and the importance of the contribution of these modes to the spectral and states densities is exhibited clearly.

The present paper concerns itself with the insulation characteristics of c-C4F8/N2 gas mixtures and studies the possibility of applying in the gas insulation of power equipments. We aim to use the theoretical framework of the Boltzmann equation to calculate the density-normalized effective ionization coefficients (α–ƞ)/N and transport parameters of c-C4F8/N2 gas mixtures for E/N values from 180 to 550 Td (1 Td = 10−17 V cm2) in the condition of steady-state Townsend (SST) experiment. From the variation curve of (α–ƞ)/N with the c-C4F8 mixture ratio k, the limiting field strength (E/N)lim of the gas mixtures at different gas content is determined. In order to confirm the validity of the results obtained, comparisons with Monte Carlo simulation and experimental data have been performed. It is found that the insulation properties of c-C4F8 and N2 gas mixtures are much better than those of SF6 and N2 mixtures for applying in the high voltage apparatus as an insulation medium, especially if we take the global warming potential into account.

We have developed a setup that offers a vacuum compatible, vibration-free experimental space with active thermal stabilization around room temperature, suitable for high sensitivity measurements. In this paper we describe the experimental setup from the thermal viewpoint and the design and implementation of the thermal control. Then we characterize the long-term performances of the control loop by using experimental data collected over 1 month: we show that our control is effective in reducing room temperature variations by a factor 100 over a few weeks, even in the presence of an internal dc heat source of 2 W.

In this work, we present various examples of assistance to the restoration of works of art by stimulated infrared thermography. We show initially that the method allows the detection of delamination located in mural paintings, such as in the “Saint Christophe” of the Campana collection of the Louvre French museum. We show then that it also makes it possible to detect delaminations or galleries of worms in marquetries. We show in a third stage that it provides for the detection of detachment of grayness in stained glasses. We show in a fourth stage that it allows the visualization of shards or metal inserts located in a Greek “panathénaque” amphora of the French National museum of the Ceramics of Sevres. We show finally, that the method permits the detection of a crack located in an ovoid vase of the same French National museum of the Ceramics of Sevres.

GaAs crystal presents some interesting perspectives for resonant biosensors due to its piezoelectric and good mechanical properties and the opportunity to bio-functionalize the surface. Moreover, GaAs can be micromachined by wet etching in several solutions, which constitutes a batch and low-cost process of fabrication. The lateral field excitation (LFE) is used to generate bulk acoustic waves. The main advantage of LFE is the possibility to measure in liquid media, moreover reduced aging and increased frequency stability are also ensured. In this study, an analytical modelization is used to determine the orientations of the vibrating membrane and the electric field that give satisfactory metrological performances. Electrical performances are discussed as a function of geometrical parameters. A simulation based on a Finite Element Modelization is performed in order to optimize the design of the resonant structure. The microfabrication process of the structure is presented. The choice of etchants is discussed in terms of etching rates and surface textures. Several steps of the fabrication of the sensing area structure are shown and characterized. Finally, the active area is fabricated according to the theoretical and experimental results of this study.

Three-dimensional atomic magnetometry scheme is proposed and experimented. The scheme uses only one laser beam and can measure three components of the magnetic field independently. Spin-exchange-relaxation-free regime is verified by magnetic resonance measurement. The open loop scale factors of −2.722 mV/nT, −1.452 mV/nT and 0.076 mV/nT for the three axes are characterized. The model considering the frequency response and linewidth variation can fit the measurement data well. As only one laser beam is required, the magnetometry is easy to be realized on chip scale and is particularly attractive for applications requiring low power, low cost and high precision at the same time.

This article describes the influence of the magnetic field on a small amount of residual Fe3+ ion impurities contained in a sapphire resonator excited on a whispering gallery mode and cooled down to 4 K. The energy levels and transition probabilities between pairs of levels of the system are calculated in order to determine the effect of the magnetic field on the maser output power and also on the pump power threshold.

In this paper, we study the optical, optoelectronic and photoluminescence properties of stain-etched porous silicon nanostructures obtained with different etching times. Special attention is given to the use of the stain-etched PS as an antireflection coating as well as for surface passivating capabilities. The surface morphology has been analyzed by scanning electron microscopy. The evolution of the Si-O and Si-H absorption bands was analyzed by Fourier transform infrared spectrometry before and after PS treatment. Results show that stain etching of the silicon surface drops the total reflectivity to about 7% in the 400–1100 nm wavelength range and the minority carrier lifetime enhances to about 48 μs.

In this work a new passivation method is proposed for multicrystalline silicon wafers. This method combines the use of porous silicon (PS) and silicon nitride (SiN) coating. SiN thin film is deposited on porous silicon by the plasma-enhanced chemical vapor deposition (PECVD) technique at low temperature and investigated as a passivating and an antireflection coating. We demonstrate that silicon nitride-covered porous silicon is capable of giving an outstanding surface passivation quality on mc-Si. PS-SiN passivation on mc-Si leads to an effective minority carrier lifetime of 100 μs, which is among the highest lifetimes attained on this kind of material. This high effective lifetime results not only from the excellent degree of surface passivation but also from the grain boundaries and bulk passivation. The surface reflectivity was dramatically reduced from 27% for untreated Si wafer to about 5% after PS-SiN coating in the 400–1100 nm wavelength range.

Investigations of surface alloys are important in various applications such as that of heterogeneous catalysis, where the electronic structure and geometric arrangement of the surface atoms strongly influence the reactions taking place on the surface. So, a deeper understanding of the physical and chemical phenomena associated with the creation of surface alloys appears to be essential in order to further progress in catalysis. In this paper, we present the calculation of vibrational properties of the Cu(1 1 0)-2×1-Pd surface alloy formed by depositing Pd atoms onto the Cu(1 1 0) surface substrate. The surface phonon frequencies and local vibration density of state (LDOS) are calculated with the use of the matching theory. New surface modes have been found on the Cu(1 1 0)-2×1-Pd surface alloy along the directions of high-symmetry ΓX¯$ \overline{{\Gamma X}}$, XS¯$ \overline{{XS}}$, SY¯$ \overline{{SY}}$ and YΓ¯$ \overline{Y\mathrm{\Gamma }}$ of the two-dimensional Brillouin zone, in comparison with the clean surface Cu(1 1 0). From the calculated local phonon densities of states (LDOS) we find that the layer DOS start to settle at the fourth layer, where there are only small differences with the bulk DOS spectrum.