Nano-imprint lithography (NIL) is one of the most promising patterning technologies, in which nano- and micro-patterns are fabricated on various substrates. NIL provides high throughput and low cost in fabricating nano-structures due to its simple process and allows resolution below 10 nm without issues of light diffraction with conventional lithographic techniques. Its patterning mechanism is based on mechanical deformation of a polymer resist, which is simply done by pressing with a mold. This patterning mechanism also enables inorganic and organic-inorganic hybrid materials to be directly patterned by NIL. This article covers the recent progress of NIL-based direct patterning techniques and their applications to devices. Recently, functional nano- and micro-patterns have been applied to various electronic devices for the enhancement of overall performance. Fabrication methods of these devices are difficult using convention lithographic techniques due to complex processes, high cost and low throughput. Direct NIL technique using functional resist can simply fabricate functional nano- and micro-structures and thus can be usefully applied to various industries.

The present work reports the temperature and frequency dependence of dielectric constant (ε′) and dielectric loss (ε′′) in binary Se98M2 (Ag, Cd and Sn) alloys. The measurements have been made in the frequency range (1–500 kHz) and in the temperature range 297–345 K. The values of dielectric constant (ε′) and dielectric loss (ε′′) were found to decrease with frequency and increase with temperature. The maximum barrier height Wm is calculated from dielectric measurements according to the Guintini equation. The results indicate that the dielectric dispersion exists in the present glassy systems in the above frequency and temperature range.

A numerical method for describing the electrical response of a Back-Gated Metal-Semiconductor- Metal Photodetector (BGMSM-PD) to an impinging optical pulse on the active region of the device is presented. In the absence of external voltage, the main mechanism for the transport of photo-generated carriers is diffusion mechanism. Two nonlinear differential equations describe the behavior of photocarriers’ densities in the device medium with respect to time and position. Having linearized the parabolic partial differential equations, the time evolution of carrier densities is calculated using the Alternating Direction Implicit (ADI) method. The numerical results show good agreement with the experimental data. Both experimental and numerical findings confirm that the electrical response of the device to optical pulses with spatial FWHM comparable with the width of the active region is dependent on pulse position on the active region. This feature of the device makes it to be a good candidate as position sensors in places where micro-positioning is required.

The fabrication of Al-pSnSe Schottky diodes and the temperature dependence of I-V characteristics in the temperature range 60 < T < 330 K have been studied. A decrease in the experimental barrier height Φap and an increase in the ideality factor n with a decrease in temperature have been explained based on barrier height inhomogeneities at the metal-semiconductor interface. It is proven that the presence of a distribution of barrier heights is responsible for the apparent decrease of the zero-bias barrier height. The voltage dependence of the standard deviation causes the increase of ideality factor at low temperatures. The mean barrier height Φbmean = 0.851 eV and the Richardson constant A* = 10.26 A cm−2 K−2 have been calculated by means of the modified Richardson plot. The value of the Richardson constant found is much closer than that obtained without considering the inhomogeneous barrier heights with that of the theoretical value.

Physical properties of pure bitumen 35/50 and polymer-modified bitumen 13/40 are studied using needle penetration test and differential scanning calorimetry (DSC). In particular, the mechanical response under indentation conditions is achieved as a function of different loads and temperatures. Our results show that lower temperature susceptibility is associated to larger loads but its change is rather small for the tested bitumens. A pure bitumen 35/50 exhibits a single glass transition temperature for different heating rate whereas modified bitumen 13/40 presents two Tg for different heating rate.

Amorphous thin films of Se100 − XSbX (X = 1, 5, 10, 15 and 20) were synthesized by flash evaporation of the premelt quenched bulk samples. The optical properties were investigated from spectrophotometric measurements in the UV-VIS-NIR spectral region using Swanepoel’s standard envelope method and related techniques. The optical band gap energy (Egopt) was evaluated from the Wemple-Didomenico (WDD) single oscillator model and Tauc’s extrapolation method in the region where the absorption coefficient, α ≥ 104 cm–1. The observed values of Egopt and oscillator energy Eo were found to decrease monotonously with increasing Sb additive. The complex dielectric constant (ε), Urbach energy (Eu), optical conductivity (σ), plasma frequency (ωp) and lattice dielectric constant (εL) were deduced for each alloy composition. The complex refractive index (n) fitted well to Sellmeier function which can allow extrapolation of n outside the measured spectral range. The observed changes in optical parameters with Sb content were explained on the basis of increased defect states and changes in cohesive energy indicators (average heat of atomization (Hs), mean coordination number 〈Z〉 and average single bond energy (Hs/〈Z〉).

Thermally evaporated thin films of Sn10Sb20 − xBixSe70 (0 ≤ x ≤ 4) chalcogenide system were subjected to X-ray diffraction studies to check the amorphous nature of all the films. The dark conductivity increases with the increase in Bi content and the calculated values of dc activation energy initially increase for smaller Bi concentration and then decrease sharply with further addition of Bi. The photocurrent in the beginning increases with time and then saturates to a constant value for all the samples. The decay portion of photocurrent has two components, fast one followed by slow decay. Photocurrent versus light intensity follows the power law Iph ∝ Fγ and the values of exponent are also discussed. Except for x = 4 composition the photosensitivity drops for all the samples as the percentage of Bi increases. The values of differential lifetime determined from the decay curves are also reported.

A model of heterogeneous, composite material is introduced, consisting of randomly distributed identical structural micro-domains endowed with electric charges or dipoles. Two cases are presented, one corresponding to a tightly packed (dense) material, another corresponding to highly-dispersed, small domains. The polarizability is computed in both cases, under the action of an external uniform electric field oscillating in time (a quasi-stationary field), and it is related to the displacement of the micro-domains from their positions of local equilibrium (translations or rotations). It is shown that the polarizability (or electric susceptibility) can exhibit characteristic (resonance) frequencies in the radio-frequency range and, even for moderate external fields, the material can undergo a displacive transition (similar to a ferroelectric transition), governed by non-linearities in the interaction energy of the micro-domains. The shift in the characteristic frequencies of the polarizability is estimated, as caused by the displacive modification.

We report on the structural, spectroscopic and radiative emission characteristics of Eu-doped BaTiO3 (BT) nanosystem as compared to the pure BT system. The structural analysis was performed by X-ray diffraction (XRD) studies where the nanoscale BT sample exhibits a perovskite structure with most intense peak along (1 1 0) plane that depicts the preferred crystallographic orientation. Also, the diffraction peak intensity was found to be suppressed for Eu-doped BT nanosystem. The nature of radiative emission was evaluated via steady-state photoluminescence spectroscopy (PL) and positron annihilation spectroscopy (PAS). The improved radiative emission response, with Eu2+ doping, was believed to be accompanied by 4f65d→4f7 transitions in case of Eu-doped BT system. Whereas, PAS lifetime study of doped sample has revealed longer lifetimes indicating thereby partial substitution of Ti4+ by Eu2+ in BaTiO3 system.

The present paper proposes a new equation utilizing the nonlocal Euler-Bernoulli beam model to investigate the linear transverse vibration of an embedded single-walled carbon nanotube (SWCNT) which incorporates an extra-added nanoparticle. The elastic behavior of the surrounding medium is simulated by the Pasternak-type foundation model. Hamilton’s principle is applied to derive the governing equation, and the natural frequencies are obtained by the Galerkin method. The numerical results are compared with the molecular dynamics (MD) simulation as well as with the local continuum approach in the previous literature, to validate the nonlocal continuum elastic model. Unlike the classical continuum model, the present new approach shows acceptable accuracy and good agreement to the MD approximation. The results indicate that the fundamental frequencies are significantly dependent on the attached mass and boundary conditions. To study the effects of supported end conditions, three typical boundary conditions, namely clamped-clamped, clamped-pinned and pinned-pinned, are simulated. It is found that an attached mass causes a noticeable reduction in natural frequencies, in particular, for the clamped-clamped boundary condition, a stiff medium, stocky SWCNT and a small nonlocal parameter. In addition, when the position of the added nanoparticle is closer to the middle point of SWCNT length, the mass sensitivity is increased. Detailed results demonstrate that the present equation-based nonlocal continuum theory can be utilized for SWCNT-based mass sensor, efficiently.

3 d transition-metallic ions doped ZnS quantum dots (Q-dots) were synthesized by the facile wet-chemical process. During synthesis, various ions, i.e. manganese (Mn2+), cobalt (Co2+) and silver (Ag+), were used and their photoluminescence (PL) response investigated. UV-vis absorption studies show that the various dopant ions can effectively tune energy band structure. The PL emission band is red shifted on Mn2+ doping (~575 nm) as compared to pure ZnS Q-dots (~420 nm) which is due to 4T1(G) → 6A1(S) radiative transitions. Blue/green-emission peaks at ~487 nm/~508 nm observed, respectively, on Co2+/Ag+ doping are probably arising from the recombination between the sulfur vacancy level and the new dopant level. Luminescence emission efficiency (LEE) is found to be maximum at 5 mol% Mn2+ doping and then decreases. On doping by Ag+ the LEE is found to be maximum at 2 mol% doping and almost completely quenched at 5 mol% doping. Contrary to the above, Co2+ quenched the overall PL.

The propagation of a cylindrically polarized vectorial (CPV) beam through uniaxial crystals orthogonal to the optical axis is studied. Analytical formulae are derived for the field components of the beam upon the propagation. Intensity distributions and degrees of polarization of the beam after the propagation are revealed by numerical simulations, respectively. It is demonstrated that the beam profile no longer remains cylindrically symmetric all along the propagation due to the effect of anisotropy of the crystal. Furthermore, it is also shown that both the beam properties and anisotropy of the crystal can affect the evolution of CPV beam. These conclusions may provide specific knowledge of the propagation properties of CPV beam by the use of the crystal as a fundamental optical element.

New complex magnetic frustrated materials La2 − xErxTi2O7 (0 ≤ x ≤ 0.075) have been synthesized by solid-solid method. The crystallographic and magnetic properties were studied as a function of substitution of the La3+ ion by the Er3+ one. All samples are found to be single phase and crystallize in the monoclinic structure with P21 space group. Magnetic measurements have revealed the presence of dominant antiferromagnetic interactions and the absence of magnetic ordering until a temperature of 2 K. The magnetic study suggests that the Curie-Weiss temperature (θCW) is negative, as expected in the frustrated lanthanide sublattice in the Ln2 – xLn’xM2O7 structure. From the frustration index f = - θCW/TN, we have deduced the presence of a strong frustration phenomenon. The critical properties of the antiferromagnetic behavior, for x = 0.025, 0.05 and 0.075 samples, have been investigated. It was found that the 2D-self-avoiding walk (SAW) model is the best one to describe the critical phenomena.

A new approach for the nondestructive discrimination between genuine wild ginsengs and the counterfeit ones by near infrared spectroscopy (NIRS) was developed. Both discriminant analysis and back propagation artificial neural network (BP-ANN) were applied to the model establishment for discrimination. Optimal modeling wavelengths were determined based on the anomalous spectral information of counterfeit samples. Through principal component analysis (PCA) of various wild ginseng samples, genuine and counterfeit, the cumulative percentages of variance of the principal components were obtained, serving as a reference for principal component (PC) factor determination. Discriminant analysis achieved an identification ratio of 88.46%. With sample’ truth values as its outputs, a three-layer BP-ANN model was built, which yielded a higher discrimination accuracy of 100%. The overall results sufficiently demonstrate that NIRS combined with BP-ANN classification algorithm performs better on ginseng discrimination than discriminant analysis, and can be used as a rapid and nondestructive method for the detection of counterfeit wild ginsengs in food and pharmaceutical industry.

Electrical breakdown for low pressure argon gas and air, using copper thin films as the electrodes, was investigated. A specially designed cathode was built from copper thin film deposited on glass by a magnetron sputtering system creating the breakdown between those electrodes. The left side of Paschen’s curve and ionization coefficient η as well as the effective electron emission coefficient γ was obtained with respect to the variation of reduced electric fields for argon gas and air for different thin films thicknesses. It is concluded that reducing the thin film thickness as an electrode leads to a decrease of breakdown voltage and amplifying secondary electron emission. In addition, the influence of the gas type on dependence of breakdown characteristics on the electrode thickness was investigated.

The author presents the results of inelastic granular flow in an annular vibro-fluidized granular bed using hydrodynamic model suitable for dense inelastic granular gas. Using the steady-state balances of mass, momentum and energy for dissipative dense gas, the physics of the vibrated bed is initially validated in comparison with molecular dynamics (MD) simulations using the observable system parameters such as packing fraction and granular temperature. The instability of the vibrated bed is also explored due to the influence of additional dissipative inner wall. The phase map of inner and outer wall dissipations shows a characteristic line of division between the single roll systems with opposite rotations. In addition to single roll, a two roll system is observed as the density of the flow increases. The results show a qualitatively similar trend as seen in MD simulations for higher cell loadings. The findings are important as the results indicate that the increase in the packing fraction, in addition to side wall dissipation, leads to complex flow instabilities in the granular flow.

A new method has been applied for determining the mean square deviation of surface roughness and the imaginary part of permittivity of the material near-surface region. The method is based on the scattering and absorption of light in waveguide systems of integrated optics. It has high sensitivity and ease of implementation. The advantages of the proposed method are confirmed experimentally.

Regular arrays of vertically aligned microstructures consisting of entangled carbon nanotubes (CNTs) of different height and contact interface were grown on Si substrates with a bimetallic catalyst by water-assisted chemical vapor deposition. The arrays of high and wide CNT blocks (150–300 μm, 50–140 μm square) showed the ability to reach high stable field emission (FE) currents per block up to 300 μA due to the presence of multiple CNT emitters. However, significant outgrowth of the CNTs and limited mechanical stiffness of such blocks led to a limited FE homogeneity and alignment of the emitters. For the arrays of small rounded CNT bundles (∼5 μm, 20 μm diameter), well-aligned and highly efficient FE with maximum currents up to 40 μA per CNT bundle have been achieved. Unusual I-V curves with current saturation, strong activation effects and glowing spots just before destruction have been observed and are discussed by means of band structure considerations.

The electron transfer between diamond (0 0 1) surface without and with various vacancy defects and adlayer with various adsorbed atmospheric species is examined based on first-principles calculations, which plays an important role for the conductivity of diamond (0 0 1) surface. The results show that the electron transfer from the perfect diamond surface (without defect in diamond surface or subsurface layer) to the adlayer varies with the adlayer adsorbed on the surface. The largest electron transfer is about 1.08e from the perfect surface to the adlayer (10) (O2, H3O+) among the possible adlayers, such as (1) (H2O, H2O), (2) (H2O, H3O+), (3) (H2O, CO2) … (20) (N2, O2), (21) (N2, N2) layers. It is found that the vacancy defect in surface or subsurface layer also affects the diamond (0 0 1) surface conductivity by increasing or reducing the electron transfer from the surface to the adlayer. It is also noted that the electron transfer increases largely in the case that the (10) (O2, H3O+) system is adsorbed on the diamond (0 0 1) surface with vacancy defect in the surface or subsurface layer, in which the electron transfer is largest with 1.27e when the monovacancy defect forms in the subsurface layer. Our study is useful to understand the conductivity of diamond surface.