Spin-polarized low-energy electron microscopy (SPLEEM) is a technique for imaging magnetic microstructures at surfaces and in thin films. In this article, principles, advantages and limitations of SPLEEM are reviewed. Several recent studies illustrate how SPLEEM can be used to investigate spin reorientation transition phenomena, to determine magnetic domain configurations in low-dimensional structures, or to explore physics of magnetic couplings in layered systems. The work highlights the capability of the technique to reveal in situ and in real time quantitative information on micromagnetic configurations and structure-property relationships. In addition, spectroscopic reflectivity measurements with spin-polarized low-energy electron beams can be a useful tool to probe spin-dependent unoccupied band structure of magnetic materials and electronic properties of buried magnetic interfaces.

In this paper, the authors present a new theory that can be applied to predetermine the value of cutoff temperature of operation (Tcutoff) of uncooled semiconductor laser diodes. Tcutoff is defined as the value of temperature of operation above which, the turn-on time delay ton of uncooled SLD will exceed the bit time interval of the injected pulse and results in an inoperable case. An analytical model is derived to represent the temperature dependence of ton. This model is used to derive an accurate one for Tcutoff and in terms of laser cavity parameters. Simulation results show that Tcutoff can be increased (improved) by increasing the injection current or biasing the uncooled SLD near threshold. The benefit of this study is that the designer could predetermine previously the requirements that should be taken into account, when considering of uncooled SLD in high-speed optical communication systems.

In this work, we present noise analysis in a Single Electron Photo-detector (photo-SET or nanopixel) able to detect one by one electron. We perform the power spectral densities (PSD) of random telegraph signals (RTSs) measured in the dark conditions and under light illumination. Photoinduced RTS can be attributed to the charging of a dot near the current path. From these results, photogenerated traps were identified. It is also found that RTS fluctuations depend on the light wavelength.

Analytical models for the piezoelectric excitation and for the wet micromachining of resonant cantilevers are proposed. Firstly, computations of metrological performances of micro-resonators allow us to select special cuts and special alignment of the cantilevers. Secondly the self-elaborated simulator TENSOSIM based on the kinematic and tensorial model furnishes etching shapes of cantilevers. As the result the number of selected cuts is reduced. Finally the simulator COMSOL® is used to evaluate the influence of final etching shape on metrological performances and especially on the resonance frequency. Changes in frequency are evaluated and deviating behaviours of structures with less favourable built-ins are tested showing that the X cut is the best cut for LGS resonant cantilevers vibrating in flexural modes (type 1 and type 2) or in torsion mode.

Herein the synthesis and the crystal growth of benzoyl valine (BV), an organic nonlinear optical (NLO) material for frequency conversion was grown by slow evaporation solution growth technique at room temperature has been reported. The compound was prepared by Stockman method of benzoylation. The solubility curve shows linear nature up to a temperature of 313 K. XRD study reveals that the crystal belongs to monoclinic system with P21 non-centrosymmetric space group. The fundamental vibrational frequency of various functional groups (400-4000 cm-1) in the crystal was determined from FTIR analysis. 1H and 13C NMR spectral studies reveal the presence of proton and carbon network in the grown crystalline sample. The optical behaviour of the crystal was ascertained by optical UV absorption spectral studies. The UV cut off region (λmax) lies around 200 nm and the crystal is absolutely transparent from 220–800 nm suggesting its application as NLO material. The thermal stability of the crystal was determined by thermogravimetric and differential thermal analyses. Laser damage threshold of BV was found to be 0.34 GW/cm2 and hence BV can be used in frequency doubler system. Photoconductivity study of BV revealed negative photoconductiviting nature of the sample. The microhardness studies confirm that BV has a moderate Vickers hardness number (VHN) value in comparison to the other organic NLO crystals.

The improvement of corrosion resistance of ZrN1-xCx films (0 ≤ x ≤ 1) on AISI stainless steel (ss) 304 is studied as a function of methane flow rate introduced into mixture of argon and nitrogen gases (Ar + N2). The films were deposited using ion beam sputtering technique at 400 °C and their corrosion resistance has been investigated via electrochemical test using 0.5 M H2SO4 solution. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed to study the micro and nano-structures of the films. Film stoichiometry was determined by Rutherford backscattering (RBS) technique using SIMNRA code. An average grain size of 7 nm was calculated for deposited films using Scherrer's formula. X-ray diffraction results showed the presence of a transition crystalline phase from ZrN to ZrC phase corresponding to the formation of ZrN1-xCx crystalline phase. The electrochemical test revealed that the film corrosion resistance increased with increasing x values. Furthermore, micrographs obtained by SEM did not indicate any damage on the sample surface due to corrosive agent attacks for x > 0.6.

Cd1-XZnXTe is one of the II-VI ternary semiconductor materials whose band gap can be tailored to any value between 1.48 eV to 2.26 eV as X varies from 0 to 1. It is promising material for high efficiency solar cells, switching and other optoelectronic devices. Cd0.4Zn0.6Te thin films have been deposited on ultra-clean glass substrates by screen printing method followed by sintering process. X-ray diffraction studies revealed that the films are polycrystalline in nature, single phase exhibiting wurtzite (hexagonal) structure with strong preferential orientation of grains along the (101) direction. The optical band gap of the films has been studied using absorption spectra by using double beam spectrophotometer. The dc conductivity of the films was measured in vacuum by two probe technique. The results of present investigation will be useful in characterizing the material Cd1-XZnXTe for its applications in photovoltaics. Sintering is a very simple and viable method compared to other cost intensive methods.

Copper nitride films were prepared on glass and silicon substrates by reactive direct current magnetron sputtering at various N2-gas partial pressures at room temperature. The N2 partial pressure influenced the structural, electrical and optical properties of the deposited films. The X-ray diffraction measurement showed the phase change of the preferred orientation of Cu3N planes of samples from Cu-rich (111) planes to N-rich (100) planes. The surface resistivity of glass substrate Cu3N films was between 1675 and 58 200 Ω/cm2 and for silicon substrate films surface resistivity was between 13.2 and 2380 Ω/cm2. As is observed surface resistivity strongly affected by structures of the films. Deposition rate was influenced by the amount of argon gas since they are heavier than nitrogen atoms changes from 43 nm/min to 26 nm/min. Calculated band gap energy of the samples show a sharp enhancement from 1.4 eV to 1.95 eV by increasing nitrogen content in working gas.

The thermal behaviour of a rotating roller, subjected to surface heat sources is studied in this paper using an analytical solution, developed for this purpose. The roller is composed of a solid cylinder, rotating with a constant angular velocity, and is heated at its peripheral surface by two different heat sources. The analytical solution is entirely explicit and does not necessitate any hypothesis neither on the speed nor on the physical or geometrical parameters of the roller. The characteristic parameters are presented in dimensionless forms and are used to analyse the temperature distribution as function of their variations. Thermal maps are also presented using the proposed solution. They show that the thermal gradients are localized at the vicinity of the friction zone, and that the thermal gradients zones decrease when the angular speed increases.

In this study TiO2 nanotubular fibers were prepared and subsequently loaded with CdS nanoparticles to obtain visible light activate nanofibers with modified structure. Preparation of TiO2 fibers was based on templating method and Liquid phase deposition technique (LPD) with cellulose fibers as templates. Using LPD, thickness of the TiO2 layer could be controlled precisely by adjusting the reaction conditions, therefore after removal of the template, the resulting material has a fibrous structure, mimicking the cellulose fibers shape. CdS nanoparticles were synthesized by thermochemical growth method and attached to TiO2 fibers through impregnation method. The pure composite nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-visible spectroscopic techniques. To investigate the photoactivity of CdS/TiO2 fibers, using MB decomposition test under visible light irradiation was studied and compared with that of pure TiO2 nanofibers and CdS nanoparticles. A possible mechanism of sensitization of TiO2 with CdS nanoparticles and visible light MB decomposition was also discussed. Photocatalytic decomposition test under visible light irradiation shows that these novel structures are appropriate for visible photocatalysis applications.

In this work, TOPO(tri-octyl phosphine oxide)/TOP(tri-octyl phosphine)-capped cadmium selenide (CdSe) quantum dots (QD's) of varied sizes (5–9 nm) prepared at different input Cd:Se precursor ratio's (1:1–2:1) using chemical route were dispersed in conducting polymer matrices viz poly[2-methoxy,5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and poly(3-hexylthiophene) (P3HT) respectively. The properties of polymer:CdSe nanocomposites are evaluated by means of photoluminescence (PL), UV-VIS absorption, Raman, Fourier transform infrared (FTIR), transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques respectively. The emission and structural properties of polymer-CdSe nanocomposites are found to be dependent on their morphology. The better quality of smallest sized CdSe QD's (size ~5 nm) in conjunction with regioregular P3HT polymer, leads to higher photostability of P3HT:CdSe QD's nanocomposites as compared to that for corresponding MEH-PPV:CdSe nanocomposites, thus making it as an attractive candidate for hybrid solar cells application.

Simultaneous measurement technique of evaluating the doped optical fibers (DOF) parameters is a suitable scheme for DOF production industries. In this paper, we introduce a novel technique to characterize simultaneously the main parameters of DOF such as absorption and emission cross-sections (ACS, ECS), background loss coefficient (BLC), and low dopant concentration using the gain equation of DOFs. We used this new method to determine the ACS, ECS, BLC in a standard sample of Al-P-Erbium doped optical fiber. The results have been analyzed and compared with other reports.

The metamaterial absorber composed of random dendritic cells has been investigated at microwave frequencies. It is found that the absorptivities come to be weaker and the resonant frequency get red shift as the disordered states increasing, however, the random metamaterial absorber still presents high absorptivity more than 95%. The disordered structures can help understanding of the metamaterial absorber and may be employed for practical design of infrared metamaterial absorber, which may play important roles in collection of radiative heat energy and directional transfer enhancement.

This paper presents a novel pulse-width modulation technique based sliding mode approach for direct torque control of an induction machine drive. Methodology begins with a sliding mode control of machine's torque and stator flux to generate the reference voltage vector and to reduce parameters sensitivity. Then, the switching control of the three-phase inverter is developed using sliding mode concept to make the system tracking reference voltage inputs. The main features of the proposed methodologies are the high tracking accuracy and the much easier implementation compared to the space vector modulation. Simulations are carried out to confirm the effectiveness of proposed control algorithms.

Synthesis and ion transport property studies on hot-pressed Na+ ion conducting solid polymer electrolytes (SPEs): (1-x) PEO: x NaPO3, where x in wt.%, are reported. The compositional dependent conductivity (σ) studies revealed SPE film: (75PEO: 25NaPO3) as the optimum conducting composition (OCC) with room temperature conductivity σ ~ 6.7 × 10-7 S cm-1, which is more than two orders of magnitude higher than that of pure PEO polymer host (σ ~ 3.2 × 10-9 S cm-1). Materials characterization and polymer-salt complexation were done with the help of XRD, FTIR, SEM, DSC techniques. In order to understand the ion transport behaviour in SPEs, the measurement on some basic ionic parameters viz. ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n), ionic transference number (tion) have been carried out using different experimental techniques. The activation energy (Ea) values involved in the thermally activated conductivity processes have been computed from “log σ - 1/T” Arrhenius plots.


This paper verifies the reliability of the numerical methods in reflecting the experimentation in the field of non-destructive testing by infrared thermography. A non-reinforced concrete slab (1 m × 1 m × 0.25 m) containing four defects was used, two of which had the void type and two had honeycombs type. The defects were situated from 5 cm and 10 cm of the surface. The response of the slab to thermal excitation was investigated by determining the variation of temperature at the top surface of defects and at the slab surface by simulation and experimentation. A good correlation was noted between the numerical results and the experimentation for the three studied durations of thermal excitation (30 min, 60 min and 90 min).

Al-17 wt.% Ni-10 wt.% Cu alloy was prepared by melt spinning technique and characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, and scanning electron microscopy. The resulting ribbon microstructure consists of intermetallic Al7Cu4Ni globular-like structure embedded within an aluminum matrix. The resulting effect of rapid solidification on mechanical properties is the enhancement of the alloy hardness up to 700 HV. The ternary phase Al7Cu4Ni exhibits hardness as high as 1300 HV.