Raman spectra of a variety of polymorphous (pm-Si:H) and amorphous silicon (a-Si:H) samples deposited by plasma enhanced chemical vapor deposition (PECVD) at different pressures were recorded in the range of 150 cm-1 to 750 cm-1 using a 514 nm excitation source. A comparison of Raman spectra between a-Si:H and pm-Si:H samples reveals significant differences. The Transverse Optical (TO) peak in case of pm-Si:H is asymmetric and shifted to higher wave numbers. In the literature, discrepancies between predictions of various quantum confinement models and experimental spectra have typically been attributed to either strain or negligible fraction of nanocrystallites. We show that a quantum confinement model along with a Gaussian size distribution is able to accurately predict particle size of nanocrystallites embedded in the amorphous matrix. The crystallite size and size distribution obtained by fitting the TO peak is consistent with high-resolution transmission electron microscopy observations. In our case typical mean crystallite size obtained is about 3 nm with FWHM of the distribution varying in the range 0.2–1 nm. A comparison of ratio of heights in TA and TO peaks of a-Si:H and pm-Si:H material indicates that pm-Si:H as a material has higher medium range order (MRO). This ratio has been used to compare the degree of MRO in pm-Si:H samples prepared under different conditions. Thus, we demonstrate that Raman Spectroscopy along with our model can be used to obtain the crystallite size distribution and provide a measure of degree of medium range order.

Current-voltage dependence for In2O3-SrOceramics contains three regions: linear at low voltages,superlinear at intermediate voltages (current is increasedstronger than voltage) and sublinear at higher voltages (currentis increased weaker than voltage). The appearance of sublinearregion after superlinear one cannot be explained by the existingtheory. Based on the experimental data (electrical measurements,SEM and XPS) a modified grain-boundary model is suggested. In themodel the additional adsorption of oxygen due to a capture ofelectrons at the grain-boundary states is assumed. Accordingly,the barrier height is increased and current is saturated.Calculated current-voltage dependences correspond experimentallyobserved ones.

In this paper, a new SPICE-compatible circuit model for low voltage, low on-resistance power FLYMOSFETs is presented for the first time. In this new structure, the improvement of the on-resistance has been obtained by inserting floating islands in the lowly doped layer. Our modelling is based on device physics, analytical study and on experimental characterization. The inter-electrode capacitances are modelled accurately as nonlinear functions, and good agreement between simulation and measurements is found.

Using both acoustic-optic (AO) modulator and GaAs saturable absorber in the same cavity, a diode-pumped doubly Q-switched c-cut Nd:GdVO4 laser has been realized. This laser can generate the more symmetric pulse with shorter pulse width in comparison with singly AO or GaAs Q-switched laser. We also made a comparison between c-cut and a-cut Nd:GdVO4 crystals and the experimental results shows that the doubly Q-switched c-cut Nd:GdVO4 laser can generate narrower pulse with higher peak power when the incident pump power higher than 3.4 W. The coupled rate equations, in which the spatial distributions of the intracavity photon density and the population-inversion density are taken into account, are introduced to theoretically analyze the experimental results, and the experimental results are in fair agreement with the numerical solutions.

Dielectric, impedance, modulus and conductivity studies were performed over temperature 35 °C–600 °C and frequency 45 Hz–5 MHz range on the Lead Potassium Lithium Niobate (Pb4.0K1.0Li1.0Nb10O30, PKLN) ceramics. These studies established the conduction ion motion and polarization mechanism in the material. The dispersive dielectric loss at high temperature reveals the ionic conductivity. From frequency variation of ε l response the pre-factor A(T) and critical exponent n(T) are evaluated, and are used in Jonscher's dielectric dispersion relation for ε' to fit with the experimental data. Complex impedance plots showed a non – Debye type relaxation, are used to evaluate the grain and grain boundary conduction and relaxation activation energies. DC and ac conduction activation energies are estimated from Arrhenius plots. Occupancy of Li+ for C-sites gave a completely filled structure and enhanced the phase transition temperature to 520 °C compared to PKN. This is supported by the conduction activation energy in ferro region is more than the para region. Also, the dc conductivity characterized from bulk resistance and Mll peak frequency. Polaron hoping mechanism at room temperature has been confirmed via the linear variation of the plot log (σ ac – σ dc ) as a function of log ω 2. Stretched exponential parameter, β(0 < β $\leqslant$ 1) has been evaluated from impedance plots, interpreted as a result of correlated motions between the Li+ ions and distribution of dielectric relaxation. Compared the results from different techniques, and discussed the conduction mechanism in the material.

Conducting poly(o-toluidine) (PoT) was synthesized from a derivative of aniline (o-toluidine) monomer by chemical oxidative polymerization method. After polymerization, the polymer prepared was then blended with Poly Vinyl Chloride (PVC) to achieve films. FTIR and UV-Visible studies were carried out to get their optical information. The blends were irradiated by Swift Heavy Ion (SHI) beam of 60 MeV C5+ ions with different fluences. Post Irradiation FTIR and UV-Visible spectroscopy were carried out on these films, which revealed changes in the band gap with irradiation. There are also changes in the functional groups, which are confirmed by FTIR spectra. Optical band gap is found to decrease at all fluences and increased with increase in fluence.

The behaviour of clays is not still well understood. Most information concerning clays has been obtained by techniques which give statistical information on the structure and chemistry. However papers have reported results from scanning and high resolution electron microscopy. This work presents a nanoscopic approach, using electron energy loss spectroscopy (EELS), of different purified clays. EELS permitted to detect all the elements found by classical chemistry at a macroscopic level. In particular it made it possible to determine the Si/Al ratio in kaolinite (Si/Al ~ 1), smectite and illite (Si/Al ~ 2). In all the cases, the K edge oxygen energy loss near edge structure (ELNES) is often similar to that of other clays we studied, but a strong heterogeneity has been observed. It was also possible to highlight an influence of the presence of iron on the profile of the oxygen peak.

Solute dispersion is studied experimentally in periodic or disordered arrays of beads in a capillary tube. Dispersion is measured from light absorption variations near the outlet following a steplike injection of dye at the inlet. Visualizations using dye and pure glycerol are also performed in similar geometries. Taylor dispersion is dominant both in an empty tube and for a periodic array of beads: the dispersivity l d increases with the Péclet number Pe respectively as Pe and Pe 0.82 and is larger by a factor of 8 in the second case. In a disordered packing of smaller beads (1/3 of the tube diameter) geometrical dispersion associated to the disorder of the flow field is dominant with a constant value of l d reached at high Péclet numbers. The minimum dispersivity is slightly higher than in homogeneous nonconsolidated packings of small grains, likely due to wall effects. In a weakly disordered packing with the same beads as in the periodic configuration, l d is up to 20 times lower than in the latter and varies as Pe γ with γ = 0.5 or = 0.69 (depending on the fluid viscosity). A simple model accounting for this latter result is suggested.