Sulfosalt SnSb2S4 films for optical and electrical applications have been prepared on glass substrates by thermal evaporation and subsequently thermally annealed in vacuum at temperatures from 100 to 200 °C. The optical and structural properties of the films were studied as a function of the annealing temperature. The SnSb2S4 films exhibit a polycrystalline structure and undergo abrupt changes in electrical and optical properties at a transition temperature of 140 °C. After annealing below the transition temperature, the films are highly resistive with a dominant amorphous component, but when annealed above this temperature, the samples exhibit p+-type semiconductor behaviour with a dominant crystalline component

The films of 1-(3-hydroxypropylamino)-9,10-anthraquinone (1) obtained by Hot Wall Epitaxy technique (HWE) have been studied for their morphological and electrical properties. The films were deposited on to the glass substrate at different temperatures kept at pressure of ~1.33 × 10−3 Pa. The powder X-ray diffraction (XRD) spectra show the polycrystalline nature of the films. The crystallanity of the films increases with the increase in film deposition temperature. Scanning electron microscope (SEM) shows that the molecules of 1 undergo uniform aggregation to form blade type crystallites with width 5.2–11.8 μm and length 32.6–90 μm at substrate temperature 348 K. The conduction in these films is ohmic in nature and both the increase in substrate temperature during film deposition and increase in absolute temperature of the films during conductivity measurement resulted in increased conductivity. The band gap lies in the range 1.25–1.44 eV

Ge nanocrystals (NCs) are produced by a dewetting process during annealing of an amorphous Ge layer deposited on an ultra thin SiO2 layer. We have investigated the characteristics of the resulting NCs as a function of the nominal Ge layer thickness. Thanks to transmission electron microscopy images, we have extracted both the wetting angle and the NCs aspect ratio. We found that these characteristics remain constant whatever is the nominal thickness in the range of 1.5 to 10 nm. These results suggest that NCs have reached their equilibrium shape. We also experimentally determined the evolution of the NCs with the nominal thickness of the amorphous layer and found a linear relation. These results are in agreement with mass conservation and energetical considerations. Moreover a memory effect was evidenced in all the samples by C − V measurements. At last, we demonstrate that the use of a patterned SiO2 surface improves considerably the ordering of NCs and reduces their size distribution. Such a process is promising for future integration of NCs in memory devices.

Formation of CoSi2 in Co implanted Si sample has been studied using glancing incidence X-ray diffraction and depth resolvedpositron annihilation techniques. The implanted sample exhibits near-surface amorphization in the temperature range between 300 K and 670 K. It is found that recrystallization of Si occurs at 870 K which inturn, triggers the formation of the CoSi2 phase at lower temperatures as compared to that obtained in thin film systems. The results are discussed in the light of enhanced intermixing brought by defect migration, associated with recrystallization.

An infinite regular three-dimensional network is composed of identical resistors each of resistance R joining adjacent nodes. What is the equivalent resistance between the lattice site $\mathaccent"017E{r}_i $ and the lattice $\mathaccent"017E{r}_j $  site, when two bonds are removed from the perfect network? Three cases are considered here, and some numerical values are calculated. Finally, the asymptotic behavior of the equivalent resistance is studied for large distances between the two sites.

Concentrators use reflection or refraction of light, or a combination of both, but concentration of light leads to a crucial heating of the cell, which involves degradation of its performance. However, solar cells especially conceived for concentration can support very intense illuminations as far as an active cooling is assured. In this work, a GaAs solar cell with Alx Ga $_{1-x}$ As window layer, operating under low injection conditions, has been studied with temperature and solar concentration. The temperature corresponding to each concentration was calculated, and then used in the calculation of photovoltaic parameters. The study was carried out under free mode conditions (without heat sink) and then under forced conditions (with a cooling system) in order to demonstrate the importance of cooling in the concentrator solar cells.The effect of series resistance on solar cell characteristics has also been studied. The simulation was carried out using SCAPS-1D simulator. The results were compared with those obtained theoretically; a good agreement was found between the two models.

The two-dimensional percolation problem with elliptical objects was studied theoretically using Monte Carlo simulation. The percolation-threshold number of ellipses was compared for the lattice model and the random-position (continuum) model, and a semi-lattice model was also introduced as a bridge between the two limiting models. The results showed a gradual transition from the lattice model to the random-position model when the positional disorder of the particles was increased. A similar transition was observed when the lattice was refined and the site-occupation probability was simultaneously decreased.

We report for the first time, to the best of our knowledge, an inexpensive fabrication procedure for obtaining perfectly coupled PbS quantum dots. Evidence of quantum dot pairing (each, 10–12 nm) was confirmed by transmission electron microscopy, and the stability with aging was checked by dark-current measurements. The method of encapsulating PbS quantum dots in a nontoxic cis-trans polymer is simple, convenient and attractive for reproducible reasons. Such coupled quantum dots are promising to act as qubits which are vital in quantum computers and qubit architecture.

In the present study, nano-ferrite of composition Mn0.4Zn0.6In0.5Al0.1Fe1.4O4 has been synthesized by co-precipitation method. Decomposition of residue at a temperature as low as 200 °C, gives the ferrite powder. The ferrite has been, finally, sintered at 500 °C. The structural studies have been made by using X-ray diffraction (XRD) technique and scanning electron microscopy (SEM), which confirms the formation of single spinel phase and nanostructure. The dc resistivity is studied as a function of temperature and values are found more than twice than those for the samples prepared by the other chemical methods ... It is found that the resistivity decreases with an increase in temperature. The initial permeability value is found to be higher as compared to the other chemical routes. The initial permeability value is found to increase with an increase in temperature. At a certain temperature called Curie temperature, it attains a maximum value, after which the initial permeability decreases sharply. Even at nanolevel, appreciable value of initial permeability is obtained and low magnetic losses make these ferrites especially suitable for high frequency applications. The particle size is calculated using Scherrer's equation for Lorentzian peak, which comes out between 55 nm–69 nm. Possible mechanisms contributing to these processes have been discussed.

The characteristics of transient, optically-induced voltages have been studied in a vicinal cut SrTiO3 single crystal. The effect is induced by pulsed ultraviolet laser irradiation at room temperature, and occurs withoutan applied bias. The duration of the measured signal agrees with that of the laser pulse. The measured voltage depends weakly on thelength and linearly on the width of the irradiated area. Based onthe off-diagonal Seebeck effect, the mechanism of such a dependenceis proposed.

Infrared to visible upconversion emission bands are observed in Nd3+: LiTeO2 glass at 430, 482, 525, 535, 580, 600, 664 and 766 nm wavelengths due to the 2P1/2 $\to$  4I9/2, 2P1/2 $\to$  4I11/2, 2P1/2 $\to$  4I13/2, 4G7/2 $\to$  4I9/2, 2P1/2 $\to$  4I15/2, 4G7/2 $\to $  4I11/2 & 4G5/2+2G7/2 $\to$  4I9/2, 4G7/2 $\to$   4I13/2 and 4G7/2 $\to$   4I15/2 transitions, respectively. Mechanisms involved in these upconversion emissions are shown to either involve excited state absorption or energy transfer depending upon the concentration of the rare earth ions. The emission bands at 755 and 968 nm are also observed due to the thermally excited phonon absorption, on excitation with 800 nm wavelength. A 90 fold enhancement in the intensity of anti-Stokes emission at 755 nm is observed in this glass when temperature is raised from 298 to 523 K. Fluorescence intensity ratio (FIR) and sensitivity (S) of the two thermally coupled levels viz. 4F3/2 and 4F5/2 are calculated at different temperatures and results show that these levels could act as temperature sensor in tellurite host. Lifetimes of the excited levels 2P1/2, 4G7/2, 4F3/2, 4F5/2 and 4F7/2 involved in the emission process are also determined and their temperature dependence is described.

Photoacoustic imaging is a noninvasive, nonionizing imaging modality that combines the merits of high optical contrast, goodultrasonic resolution and satisfactory imaging depth. These features make it suitable for detecting the pathological changes of subcutaneous vasculature. A setup of photoacoustic imaging system was employed to achieve images of subcutaneous vasculature and subcutaneous tumor-related vascular anomalies in mice in vivo. The networks of subcutaneous vasculature are clearly identified in the photoacoustic images, blood vessels which are invisible to the naked eye under the skin surface and tumor-related abnormal vasculature are also revealed by the photoacoustic system. Moreover, micro blood vessels correlated with the high frequency signals become evident after digital image processing based on high-pass filtering. This work demonstrates that photoacoustic imaging could potentially provide a valuable tool formonitoring the pathological changes of subcutaneous vasculature in earlystage.

Vegetation fires are slightly ionised gaseous medium. Omnipresent alkali metal species in plant's organic structure are the main source of thermally produced electrons in the fires. In the flames, electron-neutral particle collisions dominate other modes of particle interaction. The collision regime absorbs some of the incident energy when the fire is illuminated with electromagnetic waves. The rate of electromagnetic wave absorption in the vegetation fires has implications on the safety of fire-fighters. During wildfire suppression, radio communication blackout at vhf/uhf has been experienced. This may be partly due to thermal ionisation in the fire. In the experiment, the extent of ionisation in vegetation fires is measured using a 2-port vector network analyser. X-band microwaves are caused to propagate combustion zones of eucalyptus bark and guinea grass fires with maximum temperatures of 1114 and 1054 K respectively. Alkali content in the vegetation fuel was different. Measurements show maximum ionisation in flames produced from guinea grass, which had almost twice much potassium as that of eucalyptus bark, to be 2.63 × 1016 m−3 while that produced in eucalyptus bark flame was 1.46 × 1016 m−3.

One important mechanism in the prebreakdown phase is the quantum tunnelling of electrons from the metal cathode to the gas, lowering the breakdown voltage. Considerable departures from the classical Paschen's curve for pd lower than 1.0 Torr cm in microhollow cathodes with D = 200 μm and electrode spacing of 5 μm and 20 μm in air were observed. Fowler-Nordheim approach was employed to characterize the presence of field emission of electrons which modify the classical voltage versus current curve for pressures lower than 40 Torr.

Current source inverters (CSI) associated to rectifiers are used in variable speed drives for the propulsion system onboard ships. The complete structure will generate frequency perturbations in the entire supply system which could become undesirable. In a first part, the modulation theory is applied to the ideal structure of a converter. The designs of the propulsion transformers and of the propulsion motor are considered in order to calculate the injected currents on both sides of the converters. Finally, those results are confronted to experimental ones obtained onboard an electric ship. Those results show a complete validation of the theoretical predictions.