A compact subthreshold characteristics model for short channel fully-depleted double-gate (DG) junctionless field effect transistors (JL FETs) which is based on an approximated solution of 2 dimensional Poisson’s equation has been proposed. The derivation details are introduced and the model’s accuracy has been verified by comparison with both previous models and the TCAD simulations’ results which proves that the subthreshold characteristics such as channel potential distribution, subthrethold drain-to-source current, subthreshold slope, drain-induced-barrier-lowering and threshold voltage can be accurately predicted by our proposed compact model.

Microcrystalline titanium oxide (TiO2) particles of anatase crystal phase were prepared by the sol-gel route, varying thermal treatment conditions (400 °C and 600 °C), for a comparison purpose with commercial TiO2 (P25). Structural, optical and electrical properties were investigated for dye-sensitized solar cells (DSSCs) application. Both microcrystalline TiO2 particles, synthesized by the sol-gel method and obtained from the P25 powder were used to prepare a light scattering layer of the working electrode. The obtained electrodes were then immersed in a solution of N-719 (ruthenium) dye, at the ambient temperature, during 24 h. Finally, the DSSCs were assembled, the short circuit photocurrent, the open circuit photovoltage, and the power conversion efficiency were measured using an I-V measurement system. The overall conversion efficiencies for all elaborated DSSCs were proximate. A maximum efficiency of 2.3% was achieved for the sol-gel TiO2 thin film annealed at 400 °C, under one sun irradiation, with an open circuit voltage of 0.61 V and a current density of 6.54 mA/cm2. The higher efficiency value of the sol-gel TiO2 sample, annealed at 400 °C, was attributed to the uniformity of the prepared titanium oxide substrate, which provides a better surface for the dye absorption.

Using the method of extracting a series resistance from a p-n diode current-voltage characteristics developed earlier, parameters of low-temperature non-ohmic conduction in bases of two types of silicon diodes have been studied. In the diode of the first type, with finite value of impurity ionization energy, low-temperature impurity breakdown in the diode base is accompanied by hysteresis of its conduction; in the diode of the second type, the impurity breakdown occurs in soft form. In the pre-breakdown region, the results obtained for the diodes of both types, agree completely with existing picture of non-ohmic hopping conduction in spite of significant space inhomogeneity of the diode structures and non-equilibrium character of the transport in them. In the post-breakdown region, the certain peculiarities are available. For the first time the activationless hopping conduction has been revealed in crystalline silicon.

The aim of this work is to evaluate thermal stress of Er:YAG laser radiation on enamel and dentin of the dental. The transient state heat conduction equation for pulse wave laser regime with energy of 100 mJ, 300 mJ and steady state heat conduction equation for CW regime with powers of 1 W, 5 W was solved analytically. Then, the thermally induced stress was investigated following the calculation of the temperature distribution. Using the thermo-mechanical characteristics of the dentin and the enamel, all components of stress were obtained. The thermal stress of Er:YAG laser radiation on the enamel and the dentin calculated in this work may be useful for clinical applications.

An analytical method is proposed to address, the effects of geometry variations in piezoelectric bimorph actuators and the theory is applied to an actuator with an exponential tapered shape. Through five different examples, it is demonstrated, through theoretically calculated electric admittance spectra, that for a fixed length, the resonant frequency can be tailored by changing the tapering rate of the actuator. The theoretical predictions were also experimentally verified and excellent agreement was found. Our theoretical model provides a conventional tool for design optimization of such tapered bimorph actuators.

The spin Hamiltonian parameters (g factor and hyperfine structure constants) of Cr+ in ZnX (X = S, Se, Te) and CdTe are theoretically investigated, using the perturbation formulas of these parameters for a tetrahedral 3d5 cluster. Both the contributions from the crystal-field (CF) and charge transfer (CT) mechanisms are considered from the cluster approach. The calculated results show good agreement with the experimental data. The CT contribution to g-shift Δg (=g − gs, where gs =2.0023 is the spin only value) is opposite (positive) in sign related to the CF one, and its importance (characterized by the relative ratio (|ΔgCT/ΔgCF|) is 11%, 66% and 104% (71%) for ZnS, ZnSe and ZnTe (CdTe), respectively. ACT from the CT contribution to hyperfine structure constant is the same (positive) in sign and about 50–53% in magnitude as compared with ACF from the CF one.

Effects of X-ray irradiation on the color changes of PM-355 and Makrofol DE 7-2 nuclear track detectors have been investigated. Samples from PM-355 and Makrofol DE 7-2 polycarbonates were irradiated with X-ray doses at levels between 10 and 250 kGy. The transmission of these samples in the wavelength range 370–780 nm, as well as any color changes, was studied. The Commission International de E’Claire (CIE units x, y and z) methodology was used in this work for the description of colored samples. The color differences between the non-irradiated sample and those irradiated with different X-ray doses were calculated. The results indicate that both PM-355 and Makrofol DE 7-2 detectors acquire color changes under X-ray irradiation, but the PM-355 detector has more response to color change than that of Makrofol DE 7-2.

We report on a modified bulk heterojunction (BHJ) solar cell in which a nanohybridized composition of lead sulfide (PbS) colloidal quantum dots (QDs) and multiwall carbon nanotubes (MWCNTs) were incorporated into a standard regioregular poly(3-hexylthiophene) (rr-P3HT):phenyl-C61-butyric acid methyl ester (PCBM) blend. This hybrid ((P3HT:PCBM):PbS-QD/MWCNT) solar cell exhibits an increased power conversion efficiency (PCE) of 3.40% as compared to that of 2.57% from a controlled P3HT:PCBM standard BHJ solar cell fabricated under similar experimental conditions. The 32% increase in efficiency is effectively attributed to the extended quantum-dot-sensitization in the near-infrared (NIR) due to the absorbance of QDs/CNTs in the spectral range from 700 nm to 1450 nm. The strong conjugation, controlled coupling and nanohybridization of QDs/CNTs played an important role towards the improvement of PCE since it is proposed that excitons generated in the QDs can be efficiently dissociated at the QD/CNT interface by transferring the electrons to the CNTs followed by holes transfer to the P3HT. In this ternary blend, the staggered energy band alignment between P3HT and the QDs allows both electrons and holes transfer from the QDs to the PCBM and the P3HT, respectively. Subsequently, the dissociated carriers have been efficiently transported by the CNTs and P3HT to favorable respective electrodes.

In this contribution, the micro- and macro-structure of plasma grown hydrogenated nanocrystalline silicon (nc-Si:H) thin films were followed with respect to substrate temperature (Ts) ranging from 80 °C to 200 °C. nc-Si:H films were deposited by plasma enhanced chemical vapor deposition technique using silane gas highly diluted by hydrogen and high RF power density. Micro-structure analysis was performed with grazing angle X-ray diffraction (GAXRD) and dispersive Raman spectroscopies. Parallelly, morphological properties of the films were investigated via field emission scanning electron microscopy (FE-SEM) by taking both surface and cross-sectional micrographs. GAXRD results suggest the presence of 4–5 nm nanocrystallites with the size almost independent of Ts. The detailed analysis of the Raman spectra reveals one- and two-phonon modes due to amorphous and crystalline silicon (c-Si), where all c-Si related peaks shifted to lower frequencies. Raman nanocrystalline volume fraction is found to be greater than 50% for all Ts; it increases together with the short-range order at elevated Ts. This micro-structural improvement with Ts is considered to be slight when compared to the FE-SEM-observed drastic changes of morphology, particularly the size of large conglomerates (35–250 nm). The behavior of micro- and macro-structure with Ts is correlated well with the previously determined bonding and lateral conductivity measurements. It seems to be the macro-structure that accounts for bonding and electrical properties of nc-Si:H thin films.

Undoped zinc oxide (ZnO) thin films have been grown on glass substrates by sol-gel process associated with dip coating. Two different solvents are used such as: 2-methoxyethanol and ethanol. The influence of these solvents on structural and optical properties of ZnO thin films has been investigated. Crystallinity and surface morphology of ZnO films are analyzed using X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The optical properties are characterized by ultraviolet-visible (UV-vis) and photoluminescence spectroscopy (PL). Humidity sensors have been prepared with deposited ZnO films. Results reveal that ZnO thin film synthesized with 2-methoxyethanol showed a better crystalline quality and ultraviolet emission performance. In addition, a smaller transmittance in visible range and a higher surface roughness are observed. Sensing humidity test exhibits better sensitivity for sensor prepared with film deposited using 2-methoxyethanol as solvent.

In the present work, we study the dielectric behavior of various ternary mixtures composed of epoxy resin (RE), of one of three different titanates (barium titanate, BaTiO3; calcium titanate, CaTiO3; magnesium titanate, MgTiO3) respectively with one of three oxides (calcium oxide, CaO; manganese dioxide, MnO2; zinc oxide, ZnO) using time domain reflectometry (TDR). The different composites are mixed at room temperature in different volume fractions keeping the epoxy resin at a constant volume fraction. Several mixture combinations are studied to see the oxides influence on the titanates dielectric behavior in the range from DC to 10 GHz. This is done through the experimental determination of the dielectric constant εs. A noticeable effect has been recorded at the low frequency and which consists of an increase of this dielectric permittivity when growing the volume fraction of manganese dioxide. One meaningful point of this study is the lowest static conductivity value (8.017 × 10−3/(Ωm)) being reached with an incursion of 7.5% of MnO2 in a ternary mixture composed of RE, MgTiO3 and MnO2. In addition, the behavior obtained experimentally has been validated by the Lichtenecker modified model. This study interest lies on an application of these materials in microelectronics and particularly in telecommunication components manufacturing.

We demonstrate how the sub-threshold characteristics are affected by the density of crystalline domain boundaries directly governed by an organic semiconductor (OSC) – a gate insulator interface in a solution-processed 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) thin-film transistor (TFT). For generation of an engineered interface, a self assembled monolayer of octadecyltricholorosilane (OTS) was produced between a solution processed TIPS-pentacene film and a silicon dioxide layer. The interfacial charge trap density (Ntrap) deduced from the sub-threshold characteristics was significantly minimized after OTS treatment due to reduced crystal domain boundaries in the TIPS-pentacene film. In addition, the carrier mobility exhibits a value twice as large by OTS treatment. It is found that less crystal domain boundaries in the solution-processed OSC obtained from the engineered interface play an important role in inducing improved sub-threshold characteristics together with increased carrier mobility in organic TFTs.

A facile generic strategy of solid-state reaction under air atmosphere is employed to prepare LiNi0.8Co0.15Al0.05O2 layer structure micro-sphere as cathodes for Li-ion batteries. The impurity phase has been eliminated wholly without changing the R-3m space group of LiNi0.8Co0.15Al0.05O2. The electrochemical performance of LiNi0.8Co0.15Al0.05O2 cathodes depend on the sintering step, temperature, particle size and uniformity. The sample pre-sintered at 540 °C for 12 h and then sintered at 720 °C for 28 h exhibits the best electrochemical performance, which delivers a reversible capacity of 180.4, 165.8, 154.7 and 135.6 mAhg−1 at 0.2 C, 1 C, 2 C and 5 C, respectively. The capacity retention keeps over 87% after 76 cycles at 1 C. This method is simple, cheap and mass-productive, and thus suitable to large scale production of NCA cathodes directly used for lithium ion batteries.

Nanometric Zn1–xCoxO (x = 0.020, 0.025 and 0.030 in mol.%) nanopowders were obtained from low temperature calcination of a resin prepared using the Pechini’s method. Firing the Zn1–xCoxO resin at 400 °C/2 h a powder with hexagonal structure was obtained as measured by X-ray diffraction (XRD). The powder presented average particle size of 40 nm observed by field emission scanning electronic microscopy (FE-SEM) micrographs and average crystallite size of 10 nm calculated from the XRD using Scherrer’s equation. Nanocrystalline Zn1–xCoxO films with good homogeneity and optical quality were obtained with 280–980 nm thicknesses by electron beam physical vapour deposition (EBPVD) under vacuum onto silica substrate at 25 °C. Scanning electron microscopy with field emission gun showed that the film microstructure is composed by spherical grains and some needles. In these conditions of deposition the films presented only hexagonal phase observed by XRD. The UV-visible-NIR and diffuse reflectance properties of the films were measured and the electric properties were calculated using the reflectance and transmittance spectra.

The photoelectrocatalytic activity of Zn-loaded reduced graphene oxide-titania (RGO-TiO2) composite coatings on mild steel substrate was investigated in detail. Zn-loaded RGO-TiO2 composite films were prepared by using DC electrochemical co-deposition technique onto mild steel substrate in an acid-sulphate bath electrolyte. The cyclic voltammetry and photocurrent response studies showed that the Zn-loaded RGO-TiO2 films have improved photoelectrocatalytic performance. The embedding of metallic Zn into the RGO-TiO2 promoted an effective charge carriers separation by minimizing the recombination losses. In this manner, metallic Zn will act as efficient photo-induced electron acceptors from the bulk of RGO-TiO2 film. Thus, the transportation of the electrons from the working electrode to the counter electrode was improved significantly.

Titanium thin films were deposited on single crystal Si (3 1 1) and polycrystalline 316 LN nuclear grade stainless steel substrates by RF magnetron sputtering. X-ray diffraction revealed that, irrespective of substrate type, films exhibit preferential growth along the (1 0 0) plane. The microstructure of the films corresponds to the zone-I type in structure zone model on both substrates. The hardness and Young's modulus of the films were extracted from load-displacement curves. The maximum values of hardness and Young's modulus were 12 and 132 GPa respectively for 220 nm thin film on SS substrate. The electrical resistivity data revealed that the films are metallic in nature and the resistivity is lower in the case of the 220 nm thickness film, on both substrates. The observed changes in mechanical and electrical properties can be correlated with variations in the microstructure of Ti films.

Indium sulfide In2S3 thick films are deposited on glass substrates using spray technique over the optimum conditions experiments (Ts = 340 °C, S/In = 2). The films are polycrystalline and have thickness of about 1.8 μm. These films are annealed in a vacuum sealed pyrex tubes (10−5 torr). Physico-chemical characterizations by SEM observation, X-ray diffraction and EDX analysis are undertaked on these films. This treatment has improved crystallinity of samples. It has allowed thus to stabilize β and γ varieties of In2S3 material. In2O3 and In6S7 phases have appeared with very weak intensities at high temperatures. The best structure quality are obtained at 300 °C for the optimum annealed temperature (Ts = 340 °C, S/In = 2), for which samples are constituted in dominance by γ phase oriented preferentially towards (1 0 2). The grain size is 42 nm of this phase. Chemical composition of such films has changed relatively to non-treated film but it seems not be affected by treatment temperature. Atomic molar ratio S/In is obtained for 0.9. Optical study shows that these layers are transparent in the visible and optical direct band gap increases as function of annealed temperature.

Using the discrete ordinate method, we solve the equations of phonon radiative transfer for thin films analytically, and deduce closed-form expressions for three thermophysical properties including the phonon intensity, heat flux density and effective phonon thermal conductivity. These analytical expressions provide a fast and convenient way to analyze heat conduction behavior in thin films, and thus allowing us to comprehend how the film thickness and bulk phonon mean free path affects the thermophysical properties. Also we extend these expressions from thin films to one period of superlattices, and demonstrate that adjusting the thickness ratio of two layers can control its effective phonon thermal conductivity.

Ge quantum dot formation on Si(1 0 0)-(2 × 1) by nanosecond pulsed laser deposition under laser excitation was investigated. Scanning tunneling microscopy was used to probe the growth mode and morphology. Excitation was performed during deposition using laser energy density of 25–100 mJ/cm2. Faceted islands were achieved at a substrate temperature of ∼250 °C only when using laser excitation. The island morphology changes with increased laser excitation energy density although the faceting of the individual islands remains the same. The size of the major length of islands increases with the excitation laser energy density. A purely electronic mechanism of enhanced surface diffusion of the Ge adatoms is proposed.

Mn(II) ions doped NaCaAlPO4F3 phosphor was synthesized by using solid state reaction method. The prepared sample was characterized by various spectroscopic techniques such as powder XRD, SEM with EDS, Optical absorption, electron paramagnetic resonance (EPR) and photoluminescence. From powder XRD, the average crystallite size was calculated about 46 nm. SEM images showed the irregular shaped entities present in the sample. Optical absorption spectrum gave the absorption bands in UV-VIS region which are the characteristic of Mn(II) ions in octahedral symmetry. The room temperature EPR spectrum exhibited a six weak hyperfine splitting lines centered at g = 2.0. Photoluminescence spectrum showed the emission peaks in visible region, from yellow to red with an excitation wavelength of 465 nm. From the emission spectral data, the CIE chromaticity coordinates were also calculated as (x = 0.661, y = 0.338).