The current-voltage (I-V) characteristic of the Au/n-GaAs/Au-Ge Schottky diode with native oxide interfacial layer has been studied as a function of hydrostatic pressure. The ideality factor and barrier height of the diode have shown hydrostatic pressure dependence. The pressure coefficient of the flat-band barrier height was found to be 10.3 meV/kbar and the flat-band barrier height at zero pressure was calculated as 0.854 eV. Additionally, the energy distribution of interface state density was determined from I-V characteristics for each hydrostatic pressure value.

We study the use of a BGaN back-barrier layer in the GaN buffer of AlyGa1−yN/GaN highelectron mobility transistors to improve confinement of carriers in the 2D electron gas region. Unlike InGaN back-barrier designs, whose polarization-induced sheet charges form an electrostatic barrier at the backbarrier/ buffer interface, BGaN back-barrier designs create an electrostatic barrier at the channel/backbarrier interface. This can result in carrier confinement to sub-15 nm thickness, even when the channel is 30 nm wide. Although polarization sheet charges due to the BGaN back-barrier form a secondary well at the back-barrier/buffer interface, increasing the thickness of the back-barrier may move the secondary well so that it no longer interacts with the primary channel.

Silver (Ag) films were prepared by DC magnetron sputtering deposition at different substrate temperatures (25–450 °C) and film thicknesses (100–800 nm) and their morphological, optical, electrical and structural properties were investigated. Atomic force microscopy (AFM) was employed to study the surface topography of the thin films. The grain size as well as surface roughness of the films is strongly dependent on the temperature and the film thickness. X-ray diffraction experiments showed the intensity enhancement by increasing substrate temperature, also by increasing film thickness. The optical properties were determined by means of spectrophotometric analysis. It is found that the optical reflection is not affected significantly with substrate temperature and film thickness. The electrical resistivities of films were determined by four-point probe measurements. The experimental results indicate that the films with higher thickness and deposition temperature have the lowest resistivity.

In situ powder X-ray diffraction (XRD) studies on 3D micro-crystalline tin (II) sulfide (SnS) were carried out at different temperatures. While increasing temperature, the crystal structure of SnS remains stable as orthorhombic, whereas its lattice parameters and unit-cell volume are considerably varied. Further, these 3D micro-crystalline structures have showed a negative thermal expansion along the a-axis and positive expansion along the b- and c-axes. However, the overall drop along the a-axis of SnS crystals is nearly equal to their expansion along the c-axis. The observed changes in the structural properties of SnS micro-crystallites with temperature are discussed and reported.

By means of the new techniques of magnetically driven quasi-isentropic compression based on compact capacitor bank facility CQ-1.5 developed by us, the dynamic compression of two mixed HMX-based plastic bonded explosives (PBX) explosives is researched under ramp wave loading. A pressure of 5–8 GPa over 600–800 ns is realized on explosive samples by optimizing loading electrodes and controlling charging voltages of CQ-1.5. And loading strain rates vary from 105 1/s to 106 1/s along the thickness of explosive samples. For experiments, the particle velocities of interface between explosive samples with different thicknesses and LiF windows are measured to determine material response by a displacement interferometry technique of Doppler pins system (DPS), and the experimental compression isentropes of researched explosives are obtained using the data processing method of backward integration and Lagrangian analysis for quasi-isentropic compression experiments, which are in agreement with the theoretical isentropes based on Mie-Grüneisen equation of state (EOS) and the results by Baer. For simulations, one-dimensional hydrodynamics code SSS is used to analyze the dynamic process, and the calculated results of particle velocity of interfaces are consistent with the experimental ones. Finally, one of the explosive constituents, the binder fluoride rubber F2311, is also investigated using this technique, and some properties under ramp wave loading are gained.

n-Si/p-PEDOT-PSS heterojunction diode was fabricated by deposition of poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) onto n-type Si wafer using spin coating. Its electrical properties of the diode were investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The field emission scanning electron microscopy (FE-SEM) was used to determine the surface quality. SEM result indicates that the surface morphology of the PEDOT-PSS film spin coated on n-Si substrate is almost homogeneous. Diode parameters such as the ideality factor, barrier height and series resistance were calculated using Cheung’s method and C-V measurements. I-V characteristics under dark and illumination conditions were performed to characterize the photovoltaic behavior of the diode.

We have designed and built a hemispherical retarding field energy analyzer in order to facilitate characterization of large area electron emitters (typically field emitter arrays with active areas up to 1 cm2) with large angular aperture. A complete numerical model of the analyzer has been built, including perturbations due to secondary particles, in order to determine the analyzer performances. The analyzer energy resolution is better than 100 meV for an energy range up to 120 eV. The analyzer has a global field of view of 112° and allows measurements of the energy distribution of the beam as a function of the emission angle, as well as measurements of the beam intensity profile along any section of the beam. We have successfully used the analyzer to characterize the electron beam emitted by 1 cm2 Mo microtips-based field emitter arrays.

A one-dimensional (1D) position sensitive detector (PSD) with the active layer imbedded in resonant cavity is proposed. The lateral photovoltaic effect (LPE) on the surface of active layer is related to the lifetime of photo-generated carriers-electrons and holes pairs. Theoretically, by improving the transmittance of multiple layered systems, the lifetime of carriers can be lengthened. For a photodetector in near infrared, we design the multiple layered system stacked by alternating layers with MgF2 and InP. The calculated result of electric field distribution in the proposed PSD is maximized in active layer with appropriate thickness. By this means, our aim is theoretically accomplished to enhance LPE in PSD based on resonant cavity structure.

In device technology, the multilayer contacts provide improved performance. The comparative study of different high work function bilayer Schottky metal (Pt/Pd, Pt/Ni and Pt/Ti) contact has been taken to study the DC and RF performance of n-GaN Schottky diode. The fabricated Schottky metal contact Pt/Pd, Pt/Ni and Pt/Ti annealed from room temperature to 800 °C studied shows that Pt/Pd Schottky metal contact on n-GaN shows high thermal stability and maximum barrier height 1.10 eV, ideality factor 1.001, lower series resistance and lower insertion loss (S21 dB) at high frequency compared to Pt/Ni and Pt/Ti bilayer Schottky metal contact.

The dielectric response of the liquid crystal (LC) and LC doped with graphene was studied by using dielectric spectroscopy technique in the frequency range of 100 kHz to 10 MHz at room temperature. The LC material used in this experiment was E7 and the concentration of doping material graphene was acquired as 0.05 wt.% in E7. Dielectric constant (ε'), dielectric loss (ε"), dielectric loss tangent (tan δ) and AC conductivity of pure LC and graphene-doped LC mixture were also calculated. Results showed that all dielectric parameters are strong functions of frequency and applied bias voltage. Also, it was found that doping LC with graphene strongly influenced threshold voltage.

The reverse I-V characteristics of In-pWSe2 and Al-pWSe2 Schottky barrier diodes were investigated at room temperature with two different metal thicknesses. A model is presented on the basis of thermionic emission and tunneling to explain the unusually high leakage current observed in these diodes. It has been identified that the major contribution to leakage current is by tunneling mechanism, which significantly affects the reverse I-V characteristics of the Schottky contacts, along with a very small amount of thermionic emission current. We have also extracted various Schottky diode parameters of the two types of diodes fabricated and compared the data. It is found that the diode with 1000 Å metal thickness possesses more tunneling current compared to 500 Å diode.

The purpose of this paper is to approach stimulated infrared thermography possibilities in terms of measuring longitudinal thermal diffusivity of mural paintings in situ. The measuring method principle is first submitted. It is based on temporal analysis of changes in the characteristic radius beams of spatial profiles of the photothermal signal, measured on the spot of the laser excitation. The feasibility of the method is demonstrated, thanks to a series of simulations. Lastly, the method enables to correctly estimate longitudinal thermal diffusivity in a test sample, and further in a fragment copy of “Saint Christophe” belonging to the Campana collection in the Louvre.

This work presents additional arguments about the enhancement of optical and electrical properties of SiNWs obtained by chemical etching and the beneficial effect of the formation of ultrathin film of SiO2 by a heat treatment at 900 and 1000 °C reported recently by Karyaoui et al. in [Eur. Phys. J. Appl. Phys. 58, 20103 (2012)]. In the actual study, we report the effect of this thermal oxidation treatment on the morphological and optoelectronic properties of silicon nanowires (SiNWs). The SEM and AFM observations exhibit indeed a remarkable change of the surface shape after this oxidation. On the other hand, the LBIC measurements of the SiNWs reveal that the thermal treatment improves the optoelectronic response at 900 °C and the effective diffusion length increases from 150 μm for untreated SiNWS to 235 μm after thermal treatment.

The multilayered films-based charge trap flash memory cells were fabricated by incorporating high-k ZrO2/Al2O3 nanolaminates as charge trapping layer and amorphous Al2O3 as tunneling and blocking layers. The thickness of high-k ZrO2 or Al2O3 film in charge trapping layer after annealing treatment was about 1.5 nm for each layer. The charge storage characteristics of such memory cells were measured, and the results demonstrated that they had a large hysteresis memory window of 3.85 V at a sweeping gate voltage of ±8 V, an excellent endurance up to 105 write/erase cycles and a small charge loss of 9.6% after 10 years.

The electrical behavior of organic memory devices based on pentacene thin film transistor using polymethylmethacrylate (PMMA) as the gate dielectric is reported. Memory behaviors based on incorporating a layer of thermally evaporated metallic floating gate are demonstrated. The gate electrode was made from 50 nm evaporated aluminum on glass substrate, and the drain and source electrodes were fabricated by evaporating 50 nm gold. The effects of the insulator thickness on the stability of pentacene layer are also investigated. The memory transistors containing the floating gate exhibited clear hysteresis in their electrical characteristics (output and transfer characteristics). Under an appropriate gate bias (2 s pulses), the floating gate is charged and discharged, resulting in significant threshold voltage shifts. Pulses of 1 V resulted in clear write and erase states. The shifts in the threshold voltage of the transfer characteristics were attributed to the charging and discharging of the floating gate. The detailed programming and erasing procedures are reported.

A sintered Ti13Cu87 bi-component target was sputtered by reactive DC magnetron sputtering in nitrogen ambient under various sputtering powers. Ti included Cu3N (Ti:Cu3N) thin films were deposited on Si (1 1 1), KBr (potassium bromide), quartz and glass slide substrates. Crystalline phases of the films were identified by X-ray diffraction (XRD) technique. Crystalline quality and phase stability are strongly dependent on sputtering power. Formation of copper vacancies in Cu3N cell substituted by Ti atoms and subsequent excess of interstitial nitrogen (N-rich) result in lattice constant expansion. Bonding environment in these films was obtained from fourier transform infrared (FTIR) spectroscopy. Surface morphology of the films that were studied by a scanning electron microscope (SEM) indicates a granular structure. Atomic Ti:Cu ratio of Ti:Cu3N films, determined by energy dispersive X-ray (EDX) spectroscopy, is less than that of original target. Optical study was performed by Vis-near IR transmittance spectroscopy. Film thickness, refractive index and extinction coefficient were extracted from the measured transmittance using pointwise unconstrained minimization approach. The TiCu3N films are direct semiconductor with bandgap energy with the range of 2.79–3.34 eV. Ti incorporation and subsequent N-rich have a significant role in bandgap widening and lattice constant expansion. The films electrically show quasi-metallic behavior.

Morphological and topological quantification of complex pore networks is of great relevance for environmental engineering, earth science and industry. Recent developments of 3D imaging techniques such as X-ray microtomography or X-ray microscopy provide an opportunity to perform a comprehensive analysis of the pore network topology. Such an analysis is crucial to understand how transport or mechanical properties evolve during the growth and/or the aging of a pore network, especially near a percolation threshold. In the first part of this work, we present some properties related to the graph of retraction of a 3D pore network, a powerful way to characterize the topological evolution. In the second part, we analyze the topology of an evolving 3D pore network in the vicinity of a percolation transition. Two distinct scenarii of evolution are presented. The last part is dedicated to an experimental example of evolving pore network: the setting of an ordinary cement paste probed in its early age by synchrotron X-ray microcomputerized tomography.

To study the gas sensing properties for CO2 and NH3 gas, powdered gold nanocomposite polyaniline was chemically synthesized and ultrathin films were fabricated. XRD spectra of these samples indicate the polycrystalline nature of the film. UV-vis spectra showed peak at 3.8 eV corresponding to π-π* transition. The relative sensitivities of the gas to air were around 70 and 530 for CO2 and NH3 gas respectively. Temperature variation of gas conductivity showed the increase of conductivity of the films up to about 42 °C and then decreased for small change of temperature. Recovery time for the sample was 54 s.

Au/SiO2/Si interdigital electrodes with thickness of 1 μm were created on silicon substrate. Graphene oxide (GO) sheets hanging from these electrodes were obtained by spin coating of chemically synthesized GO dispersed in water. We used UV-light-induced photo-catalytic activity of titanium oxide nanoparticles to reduce the GO layer. Effects of the photo-induced chemical reduction on the conductivity of the GO were investigated. Also, low power DC plasma was used for oxidation of the sheets. Oxygen bombardment leads to sheets with low electrical conductivity. Measurements show that graphene and GO sheets with the controlled electrical conductivity were obtained by these processes. Scanning electron and atomic force microscopy were used to study the morphology of the TiO2/GO and graphene structures. X-ray diffraction and Raman scattering analysis were used to verify the structural characteristics of the prepared sheets. Analysis showed a gradual increase in the number of C-O bonds on the surface of the graphene layer as a result of increasing the time of plasma bombardment. Based on the Raman spectroscopy, the photo-catalytic activity of TiO2 nanoparticles resulted in a decrease in the number of C-O bonds.