In this paper the remote surface roughness effects on channel electron density of nano MOSFET is discussed by solving the coupled Schrödinger equation and Poisson equation. The results demonstrate that the remote surface roughness could largely affect the density of inversion channel electron, and the change of electron density by this effect has been found to have approximately linear relationship to the remote surface roughness. This implies that the mobility degradation effect by remote surface roughness scattering can be partially erased for the on-state current.

We report on microstructures of HfAl2O5 gate dielectric film grown on Si substrate with a Ti capping layer treated with rapid thermal annealing process. X-ray reflectivity, atomic force microscopy and X-ray photoelectron spectroscopy are used to investigate the sample. Results show that a Six(SiO$_{2})_{(1-x)}$ layer naturally forms at the interface between the HfAlO layer and the Si substrate in the as-grown sample. With the help of the Ti capping layer on the HfAlO/Si, the annealing treatment can effectively remove the Six(SiO$_{2})_{(1-x)}$ interface layer, which enhances the capacitance of the dielectric film. On the other side, the annealing process roughens the interfaces of the sample, which brings into the increase of the leakage current. Higher temperature of the annealing treatment results in rougher interfaces. Thus, the annealing temperature should be chosen properly to improve the capacitance of the film, before the interface roughening works to increase the leakage current. In this way, the dielectric and structural properties of the samples can be optimized.

In this paper, we first fabricate and demonstrate the InGaP/GaAs camel-like gate field-effect transistor with InGaAs pseudomorphic heavy-doped channel. Due to the large gate potential barrier for the use of the n+-GaAs/p+-InGaP/n-GaAs camel-like gate and the thin as well as heavy doping n+-InGaAs channel layer, the effective conduction band discontinuity $(\Delta E_c)$ is substantially extended and a high gate turn-on voltage up to 2.0 V is obtained. The device exhibits a relatively broad gate voltage swing resulting from the high gate turn-on voltage. In addition, a maximum drain current of 393 mA/mm and a maximum transconductance of 96 mS/mm are measured. These results indicate that the studied device is suitable for signal amplifier and linear circuit applications.

Thin Films of Azo Dye (1-Phenylazo-2-Naphthol) have been prepared by thermal evaporation technique onto quartz substrates held at about 300 K during the deposition process with different thicknesses range 625–880 nm. X-ray diffraction and the differential thermal analysis showed that the Azo Dye sample is crystalline nature and thermal stable in temperature range from room temperature to 100 $^{\circ}$C. The optical constants (the refractive index n, the absorption index k and the absorption coefficient α) were calculated for Azo Dye (1-Phenylazo-2-Naphthol) thin films by using spectrophotometer measurements of the transmittance and reflectance at normal incidence in the spectral range 400–2200 nm. The obtained values of both n and k were found to be independent of the film thicknesses. The refractive index has anomalous behavior in the wavelength range 400–1000 nm besides a high energy transition at 2.385 eV. The optical parameters (the dispersion energy Ed, the oscillation energy Eo, the room temperature optical dielectric constant $\varepsilon_{l}$, the lattice dielectric constant $\varepsilon_{L}$, the high frequency dielectric constant $\varepsilon_{\infty}$ and the ratio of carrier concentration to the effective mass $N/m^{\ast}$) were calculated. The allowed optical transition responsible for optical absorption was found to be direct transition with optical energy gap of 1.5 eV for Azo Dye sample. The band tail obeys Urbach's empirical relation.  

Optical properties of 4-tricyanovinyl-N, N-diethylaniline thin films were investigated using spectrophotometric measurement of transmittance and reflectance at normal incidence of light in the wavelength range of 200–2500 nm. The optical constants (refractive index, n, and absorption index, k) were calculated using a computer program based on Murmann's exact equations. The calculated optical constants are independent of the film thickness and their values are decreased by annealing temperature. The optical dispersion parameters have been analysed by single oscillator model. The type of transition in as-deposited films is indirect allowed with a value of energy gap equals to 1.45 eV, which increased to 1.51 eV upon annealing.

3-aminophenol, an organic nonlinear optical material for frequency conversion was prepared by crystallization from aqueous solution XRD pattern reveals that the grown crystal belongs to orthorhombic system having non-centrosymmetric space group of P21ab. Functional groups are identified by analyzing the vibrational spectrum. Decomposition mechanism and melting point of the title compound were found using thermal measurements. The range and percentage of transmittance is determined by recording UV-VIS spectrum. The photoluminescence spectrum explains the transition mechanism of ions. Charge transfer π-electron chromophores are characterized by molecular first hyperpolarizability (second order optical non-linearity) values approaching 1.5509 × 10−30 esu for the title compound, which is nearly 5.3 times greater than that of urea. The hybrid Hartree-Fock exchange-correlation functional is used in conjugation with 3–21 G (d) basis set for hyperpolarizibility calculations. Nonlinear optical (NLO) study using Kurtz and Perry technique have been carried out to confirm the preliminary SHG property. Dielectric measurement was also performed to study the distribution of charges within the crystal. The mechanical strength of crystal is calculated.

Transient and steady state currents in polyethylene, under low and high dc voltages, are studied. In fact, a bipolar transport physical model is developed in order to characterize the space charge dynamics within an additive-free polyethylene film, under trapping and recombination mechanisms. The numerical computational models, used for the bipolar transport of carriers, are applied to the Poisson's, the continuity and the transport equations with the appropriate physical conditions. The principal and the new numerical results are calculated especially when high dc voltages are applied. Indeed, the net charge density numerical profiles show the appearance of the space charge packets that are revealed for the first time in numerical modelling although they have long been reported in experimental works. These space charge packets induce some new aspects on the external transient current evolutions, produce the oscillations of the conduction and the displacement current before the steady state, and generate a conduction regime that is dominated by the interface electrode-insulator. These numerical results are consistent with those reported in some experimental works. However, under low dc voltage the space charge packets disappear and the space charge limited current aspect appears on the external current profile.

Following the concept of remote circular electromagnetic cloaks [Phys. Rev. Lett. 102, 093901 (2009)], here we exploit theoretically a class of rectangular cloaks that can acoustically cloak an object outside the cloaking shell. The cloaked object is no longer deafened by the cloaking shell, which is distinctly different from the existing acoustic cloaks. The function of such cloaks is justified by full wave simulations based on the finite element method. This work makes it possible to propose some applications like the stealth of submarines, which receive any incoming acoustic waves while keeping themselves undetectable to enemy's sonar devices.

Nanocrystalline silicon films were deposited by a picosecond laser ablation on different substrates in vacuum at room temperature. A nanocrystalline structure of the films was evidenced by atomic force microscopy (AFM), optical and Raman spectroscopies. A blue shift of the absorption edge was observed in optical absorption spectra, and a decrease of the optical phonon energy at the Brillouin zone centre was detected by Raman scattering. Early stages of nanocrystalline film formation on mica and HOPG substrates were studied by AFM. Mechanism of nanocrystal growth on substrate is discussed.

Titanium-doped LiCoO2 thin films were grown by pulsed laser deposition technique on silicon substrates. Structure, AFM, FTIR, Raman and Optical properties were studied with respect to their deposition parameters i.e. substrate temperature $(T_{s})$ and oxygen partial pressure $(p_{{\rm O}_{2}})$ in the deposition chamber. The films deposited in $p_{{\rm O}_{2}}= 100$ m Torr showed good crystallinity on silicon substrates maintained at $T_{s}= 700$ °C. It was found that such a film crystallizes in the layered α-NaFeO2 structure. The influence of titanium doping on particle size and morphologies has been clearly studied. FTIR spectra displayed the characteristic IR dominant bands at 246 and 550 cm−1 for titanium doped LiCoO2 thin films. The Raman peaks observed for the films at 594 cm−1 and 485 cm−1 are ascribed to Raman active modes A1g and Eg respectively. The influence of titanium doping on the physical properties has been systematically studied.

Zinc nitride (ZnN) films were prepared by electron beam evaporation technique. The effect of heat treatments on the structural and optical properties of these films were studied. The as-deposited films show amorphous structure and some peaks which are related to Zn3N2 and ZnO can be observed for annealed films. The study of the optical gap shows that these films have direct optical band gap about 3.2 eV at temperature 350 °C. At high temperature, the ZnN films become more opaque and resistive. Other optical parameters such as refractive index, extinction coefficient and dispersion parameters were investigated as a function of annealing temperature.

We consider an elongated printed circuit board (PCB) whose long edges are support-free and the short edges are either simply supported or rigidly clamped. The board experiences a significant impact loading applied to the short edges. In such a situation the reactive in-plane (“membrane”) forces (stresses) are large and result in a geometrically nonlinear dynamic response of the board. The analysis is limited to the fundamental mode of vibrations, and the method of principal coordinates is used to evaluate the dynamic response of the board. The objective of the analysis is to find out if it is sufficient to consider the nonlinear behavior of the principal coordinate (because of the in-plane stresses) only, or it is necessary to account also for the effect of these stresses on the coordinate function. Based on the developed simple and physically meaningful analytical (“mathematical”) stress model, we conclude that the effect of the in-plane tension on the coordinate function does not have to be considered for a simply supported board, but has to be accounted for in the case of a clamped board. This could be done, if necessary, using the results of the analysis.

Semiconductor nanoparticles of ZnS:Co are synthesized by wet chemical method at room temperature. The effects of increasing cobalt ions dopant in PL ZnS particles are studied, and the distribution, absorption, excitation, emission, and structural properties of particles have been determined. XRD investigation shows the cubic structure of ZnS nanoparticles and doping has no effect on the structure and the average crystalline particle size of the doped and undoped ZnS nanometerscale samples is about 2.5 nm. TEM shows the 1–3 nm size for ZnS:Co nanoparticles. UV-visible is used to study the optical absorption of ZnS pure as well as doped nanoparticles. Furthermore, as the chemical parameters change, the size of quantum dots changes systematically. Of course, doping percentage is a significant parameter in photoluminescence properties of quantum dots, but it has no effect on the size. The maximum intensity of photoluminescence spectra obtains the at 0.1% molar of the Co dopant in ZnS:Co (Ex = 283, Em = 485.423 nm) that shows the quenching point. The intensity of the emission bands decreases with the increasing of the doping percentage continuously, which indicates that cobalt ions are the eliminators of the photoluminescence.

A novel red phosphor Ba2ZnSi2O7:Eu3+ has been synthesized by sol-gel method. The crystallinity, particle size, morphology, chemical composition and luminescent properties were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), energy-dispersion spectrum (EDS) and spectrofluorometer, respectively. The results of thermogravimetric (TG) and XRD indicated that the Ba2ZnSi2O7:Eu3+ phosphors crystallized completely at 900 °C. The luminescent properties of phosphor showed red emission is obtained by exciting at 394 and 465 nm which are owing to the sharp 7F0$\to$5L6 and 7F0$\to$5D2 lines of Eu3+. Two strongest lines at 394 and 465 nm in excitation spectra of the phosphor match well with the two popular emissions from near-ultraviolet (UV) and blue GaN-based light emitting diodes (LEDs), so it could be used as red components for white LEDs.

Multiwalled carbon nanotubes are grown on nickel-seeded silicon substrates using plasma-enhanced chemical vapor deposition method at a temperature of 650 °C utilizing a mixture of acetylene and hydrogen. Magnetic and electric fields were used to obtain well-oriented carbon nanotubes. The direction of growth was found to strongly depend on the directions and magnitudes of the applied fields. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) have been used to investigate the grown nanotubes. The SEM and TEM images of as grown nanotubes show that applying magnetic field during the growth process affects the growth direction of the nanotubes and, furthermore, bent nanotubes can be achieved by changing the direction of the applied electric field alone. Raman spectroscopy has been used to analyze the structure of the samples.  

We propose a new technique for measuring the frequency stability of cw laser radiation. The technique relies on using the laser to be tested as a coupling laser in a scheme of electromagnetically-induced transparency (EIT), either on a $\Lambda $ or a ladder system. A second, frequency tunable laser (stabilization of this laser is not needed) is used both to act as the EIT probe laser, and to form an atomic frequency reference spectrum. The frequency stability is monitored via the frequency deviation of the EIT resonance with respect to an atomic reference frequency. We also present an improved dichroic atomic vapor laser lock (DAVLL) method for frequency stabilization based on a nanocell with a $\lambda /2$ thickness.

The defect structure and the EPR parameters (the g factors, the hyperfine structure constants and the superhyperfine parameters) for the tetragonal Ir2+ center in AgBr are theoretically investigated using the perturbation formulas of these parameters for a 5d7 ion in tetragonally elongated octahedra. In the calculations, the contributions from the ligand orbital and spin-orbit coupling interactions and the local lattice (elongation) distortion due to the Jahn-Teller effect are taken into account. Related molecular orbital coefficients and the ligand unpaired spin densities are determined quantitatively using a cluster approach. The impurity center is attributed to the substitutional [ IrBr6] 4− cluster on host Ag+ site, which suffers the relative elongation of about 0.08 Å along C4 axis due to the Jahn-Teller effect. The calculated EPR parameters based on the above Jahn-Teller elongation show good agreement with the observed values.

The influence of cooling rate on the structure, melting, hardness and indentation creep behavior of the Sn-0.7Cu-0.5Zn lead-free solder alloy has been studied by XRD, DSC and Vickers microhardness tester, respectively. The study was carried out for the alloy prepared at two different cooling rates of 3.5 °C/s and 11.7 × 10−3 °C/s. The results showed that the cooling rate significantly affects the structure, melting and mechanical properties of this alloy. Cu atoms are restricted in the formation of the intermetallic compound (IMC) Cu6Sn5 embedded in Sn-matrix in the slow cooled sample. Cu3Sn compound was detected in the fast cooled sample. The Zn-phase has not been detected by the X-ray diffraction analysis, which means a complete solubility of Zn in Sn-matrix has been obtained. The crystallite size of the Sn-matrix phase in the slow cooled sample was found to be 54.4 nm, while the value of the fast cooled sample was found to be 48.5 nm. This means the fast cooling condition caused grain refinement. This refinement leads to decrease the melting point from 222.7 to 221.2 °C and increase microhardness from 16.4 to 18.2 kg/mm2. Furthermore, fast cooling condition improved the creep resistance of Sn-0.7Cu-0.5Zn alloy than that of the slow cooling condition.

An analytical iterative algorithm for fast computation of scattering from multiple conductive cylinders is developed. It takes account of the independent 1st-order, coupling 2nd-order and higher-order scattering of multiple objects. The 1st-order scattering, as independent scattering of a single object self, is derived by using the expansion of cylindrical waves in local coordinate of the object, which are solved by the boundary conditions. Exciting by the 1st-order scattering from one object, the 2nd-order scattering of multi-objects are obtained iteratively using the addition theorem of Hankel function and the boundary conditions. The same approach is applicable to calculations of the 3rd-order and higher order scattering. It is found that the phase differences caused by the cylinder centers indicate the scattering wave interferences of multi-objects. Comparison with numerical MoM results well validates the analytical iterative algorithm, which significantly accelerates the scattering computation for wide-band frequencies f and overall azimuth angles θ over 360°. In order to depress the ringing effect caused by the abrupt change of scattering field in computed region to zero field in uncomputed region, the Hamming window is used to make gradual change of the scattering field to zero. Using FFT and 2D spline interpolation, discrete scattering data over the $f-\theta$ plane yield uniform discrete data over the X − Y plane. The image reconstruction is finally performed for multiple conductive cylinders. The image can well identify the positions and sizes of multi-objects.

Depleted uranium (U$^{238})$ is used for pre-ionization in the neon gas to study the soft X-ray emission in a Mather type plasma focus of 3.3 kJ. The X-rays are detected using an assembly of Quantrad Si pin diodes, masked with differential Ross fitters, and with a multi pinhole camera. The X-ray yield and pinhole images are found strongly influenced by the preionization and the pressure of the working gas. The soft X-ray yield of 82.5 ± 4.0 J in 1.3–1.56 keV energy window is obtained in the case of preionization of neon gas at the optimum pressure of 5 mbar, leading to the conversion efficiency of 2.5% of the stored energy. The total yield with preionization is 195 ± 9.0 J in 4π geometry measured at the optimum pressure of 5 mbar giving conversion efficiency of 5.9%. The time integrated images indicate the broadening of X-ray emission zone with preionization.