Growth of the ternary semiconductor Znx Cd $_{1-x}$ S in MOR type zeolite matrices is reported. Hydrothermal synthesis was used for growing such semiconductor compound and analogues by using Cd and Zn salts as well as Thiourea as precursor sources of Cd, Zn and S elements, respectively. Following synthesis routes previously reported, bulk CdS with a band gap of 2.26 eV was obtained to be used as a reference. The final products were mainly characterized by Raman and Photoluminescence spectroscopies. The study shows the formation of Zn diluted ZnCdS ternary alloy in the final products of the synthesis, particularly for those samples with a Zn(wt%)/Cd(wt%) ratio higher than 0.05, and also the formation of a ZnO phase with a band gap value around 3.3 eV for the sample with the highest Zn content.

The present work reports the temperature and frequency dependence of a.c. conductivity in glassy Se70Te30−x Znx (x = 0, 2, 4 and 6) alloys in the temperature range 300–500 K and frequency range 1 kHz. An agreement between experimental and theoretical results suggests that the a.c. conductivity behaviour of the present samples can be successfully explained by correlated barrier hopping (CBH) model. The density of defect states has been determined using this model for all the glassy alloys. The results show that bipolaron hopping dominates over single-polaron hopping in this glassy system. This is explained in terms of lower values of the maximum barrier height for single-polaron hopping.

The morphology and optical response of Au and Agnanoparticles capped with dielectric amorphous Si3N4,BN, and Al2O3 layers are studied. Quantitative analysisof high-angle annular dark-field images obtained in a scanningtransmission electron microscope and simulations of opticaltransmittance spectra are used to investigate the dependence ofthe morphology of the nanoparticles on the particle size and onthe capping material. It is demonstrated that capping-layereffects induce a size-dependent and cap-dependent reshaping of thenanoparticles.

A comprehensive analysis on the amorphous to crystalline phase transformation in Pb:GeSbTe chalcogenide alloy has been discussed. The structure identified with X-ray measurements has been discussed in relation to thermal analysis carried out on bulk samples. Optical constants have been calculated in the 350 to 800 nm wavelength range, using Fresnel's equation. The effect of Pb substitution on the optical contrast in terms of change in reflectivity and optical parameters (viz. refractive index, extinction coefficient) has been discussed. Marginal decrease in the optical contrast has been observed with a small increase in Pb content, which is effective to maintain the sufficient signal to noise ratio for optical phase-change storage.

Organic photovoltaic cells based on the multilayers structure, indium tin oxide (ITO)/copper-phthalocyanine(CuPc)/fullerene(C60)/aluminium tris(8-hydroxyquinoline) (Alq3)/aluminium, have been studied. When an ultra-thin metal layer is deposited onto the surface of the ITO anode the power conversion efficiency of the cells is significantly improved. The improvement depends on the ITO used. These differences have been attributed to the difficulty to control the surface chemistry of ITO. The best result has been obtained with a gold layer thick of about 0.5 nm. We propose that the gold ultra-thin film, which is too thin to be continuous, allows to improve the agreement between the work function of the anode and the highest occupied molecular orbital (HOMO) of the organic donor CuPc and to passivate the surface contamination of ITO.

Nanodots forming dense assembly on a substrate are difficult to characterize in terms of size, density, morphology and cristallinity. The present study shows how valuable information can be obtained by a combination of electron microscopy techniques. A silicon nanodots deposit has been studied by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) to estimate essentially the dot size and density, quantities emphasized because of their high interest for application. High resolution SEM indicates a density of 1.6 × 1012 dots/cm2 for a 5 nm to 10 nm dot size. TEM imaging using a phase retrieval treatment of a focus series gives a higher dot density (2 × 1012 dots/cm2) for a 5 nm dot size. High Resolution Transmission Electron Microscopy (HRTEM) indicates that the dots are crystalline which is confirmed by electron diffraction. According to HRTEM and electron diffraction, the dot size is about 3 nm which is significantly smaller than the SEM and TEM results. These differences are not contradictory but attributed to the fact that each technique is probing a different phenomenon. A core-shell structure for the dot is proposed which reconcile all the results. All along the study, Fourier transforms have been widely used under many aspects.

Polymer sheets are currently used worldwide in a wide range of applications. The manufacturing process of these sheets involves extruding machines that stretch the material in both lateral and longitudinal directions with respect to the machine direction, thus inducing birefringence. In most cases, the film obtained is optically biaxial. Polarimetric spectroscopy (Ellipsometry and Mueller Matrix) combined with conoscopic observation are the methods of choice to study these properties. In this work we report an analysis of commercially available polyethylene terephtalate (PET) films used as substrate for food packaging as well as for embedded electronic devices such as solar cells or flexible displays. Initial observation of these films through polarizing microscope in conoscopic mode reveals first the trace of optical axis plane with respect to the film surface and second, whether the optical axis is acute or not. This preliminary study allows optimal sample positioning for further polarimetric studies. The measurements and modelling are done in both reflection and transmission mode on several spectroscopic polarimetric setups from UV to NIR. The models give as a main result, the dielectric tensor of the film as well as its orientation with respect to the laboratory reference frame.

Using ab initio calculations, we have performed a study of the hydrostatic pressure effect on the equilibrium volume, lattice parameters, elastic modulus, and elastic anisotropy of selected M2AlC phases with M = Ti, V, Nb, and Ta. The deviations of our calculated volume change are lower than 3% comparing with experimental measurement, lead to a discrepancy in the bulk modulus less than 15%. Our results show a linear pressure dependence of the elastic modulus and the bulk modulus. Shear elastic anisotropy factor increase with the pressure enhancement, while the compressibility anisotropy remains constant around weak values.

Kinetic electron emission from MgO film under the impact of 50–300 eV rare-gas ions has been investigated by Monte Carlo simulation. The program includes excitation of the target electrons (by projectile ions, recoiling target atoms and fast primary electrons), subsequent transport and escape of these electrons from the target surface. Potential electron yields due to Auger neutralization of various ions are obtained by comparing the calculated kinetic electron yield with the experimental data. The program generates partial yields of the secondary electrons excited by projectile ions, recoiling target atoms and electron cascades. The partial yields of the electrons excited by projectile ions and electron cascades fluctuate with mass of the projectile ion like the electronic stopping. Moreover, lateral and depth distribution of the electrons excited by three excitation processes were quite different. For the range of investigated ion energies, the average electron escape depth was independent of the mass of the incident ion, which indicates that electron escape depth is a material property.

The characterization and properties of InN thin films grown on GaN templates by metalorganic chemical vapor deposition (MOCVD) at various growth temperatures were investigated. Their carrier concentrations ranged from 4.6 × 1018 to 4 × 1019 cm−3and mobility valued from 150 to 1300 cm2/V s. The variation of the growth temperature brought about different growth rates. It was also found that growth rate is increased with the increasing growth temperature and reached 470 nm/h for the InN epitaxial layer grown at 675 °C. The surface roughness of InN layers was obtained from AFM measurement. The structural quality of the InN layers was determined by TEM. The surface and cross-sectional morphologies of these films are evaluated by SEM. The layer crystalline quality was investigated by means of X-ray diffraction in the rocking curves. Photoluminescence measurements performed at 7 K and room temperature gave emission peaks at around 0.7 eV.

Confocal microscopy has been used to study the crystallization of two colloidal model systems that are geometrically frustrated in a completely different way: (I) hard colloidal polyhedrals, where crystallization is frustrated due to the incommensurate particle shape and (II) large spherical impurities in a sea of monodisperse colloidal hard spheres, where crystallization is frustrated by the introduction of impurities. As a reference system, we analyzed the crystallization of pure monodisperse colloidal hard spheres. We show that although the crystal structures of both systems are highly dissimilar on the individual particle level, both sources of geometrical frustration have a similar effect on the structure on the grain level. We quantitatively characterize the polycrystalline structures and study the crystallization process in time. Whereas grain boundaries persist in the frustrated systems due to structural arrest, the majority of grain boundaries anneals out quite rapidly in the reference system. Therefore, we argue that both sources of geometrical frustration cause a polycrystalline structure.

Well-aligned ZnO nanocones were self-assembled on amorphous carbon using manganese oxide assisted thermal chemical vapor transport and condensation, without any metal catalysts. Compared with the ZnO nanowires fabricated without the manganese oxide assistance, the field emission performance of the ZnO nanocones was greatly improved, lower turn-on electronic fields and higher current densities were achieved with these emitters. Experimental analyses showed that the ZnO nanocones grow vertically and epitaxially on the [0002] oriented ZnO intermediate layer between nanocones and substrate The manganese oxide seems to play a crucial role in the formation of this ZnO intermediate layer.

We report a tomographic diffractive microscope, which permits imaging non-labelled transparent or semi-transparent samples. Based on a combination of microholography with a tomographic illumination, our set-up creates 3-D images of the index of refraction distribution within the sample. One acquires successively interferograms, rotating the illumination (the specimen being static) and using phase-shifting holography. Within the first Born approximation, each interferogram is interpreted as a subset of the Fourier transform of the specimen index of refraction distribution. The reconstruction is therefore similar to synthetic aperture imaging: one recombines the information in the Fourier space, and a final Fourier transform gives a 3-D image of the specimen. First recalling the theoretical foundations, we then describe our experiment, and show initial results obtained on biological samples.

The variable angle spectroscopic ellipsometer in conjunction with computer simulation were employed to determine the optical constants of ZnO in the ZnO/Ag/ZnO (ZAZ) multilayer system. A five-phase, glass/ZnO/Ag/ZnO/air, model was used to fit the calculated data to the experimental spectra. The ellipsometrically determined ZnO and Ag layers thicknesses were found to be agreed well with those previously determined by X-ray reflectivity. The effects of Ag layer thickness (Agd ) and ZnO top layer thickness (ZnOd ) on the optical constants of ZnO in the ZAZ multilayer system were discussed. The refractive index values determined at 550 nm, remains almost constant as Agd increases while the refractive index values decrease with decreasing ZnOd . Over the whole visible spectral range the extinction coefficient values of the Agd group are very close to zero and does not depend on Agd while the extinction coefficient values of the ZnOd group increase with decreasing ZnOd . The optical band gap values are found to be affected strongly by both Agd and ZnOd .

Wavelength dispersive and energy dispersive spectrometers were fitted on a scanning electron microscope (SEM) in order to perform combined analysis and to use the advantages of the two spectrometers. The combined system is simple, adaptable to a lot of SEM and cheaper than Electron Probe Micro Analyzer (EPMA). Its originality is to combine two spectrometers: a parallel beam WDS with a silicon drift EDS spectrometer. This makes analysis easier (easy to find the optimum parameters to set up, as beam current) and saves time. With this system, quantitative analysis is more accurate than with EDS alone, better resolution can be achieved, less overlap of lines and better spatial resolution can be obtained. A sample recently studied by a microanalyst association was analysed with the present system in order to test its efficiency. In a second series of analyses, a sample showing difficulties (peak overlaps, small phases, low mass fraction) was analysed and good results were achieved.

The fabrication of a hybrid micro/nano-fluidic device to study electropreconcentration of biomolecules is presented. A nanoslit surrounded by glass is formed between two access microchannels and an “H” configuration bio-analysis system is developed. The optimized know-how for this biochip fabrication is transferred and the key steps are discussed. Fluorescence spatiotemporal profile in the preconcentration area is recorded and quantitatively analyzed. The reliability of the applied technology for studies of charged biomolecule transport phenomena across nanochannels is proven giving two examples for different preconcentration geometries.

The use of additives which raises the density of metal-ion in electroforming solution and the application of impulse current are the common methods to improve the deposition rate of electroforming and to ameliorate the mechanical characteristics of electroforming layer. However, our study reveals that it is possible to obtain better results by tailoring the flow rate of the electrolyte and the relative intensity of the electric and applied magnetic fields. The MHD (Magnetohydrodynamic) effect arising from the application of an external magnetic field can have remarkable influence on the crystal behavior, giving more consolidated textures while providing higher deposition rate and better mechanical properties of the Ni–Co–Mn alloy.

Effects of plasma power on the growth of the multi-wall carbon nanotubes (CNTs) are reported. CNTs were grown on the silicon wafers by plasma enhanced chemical vapor deposition (PECVD) method using a mixture of acetylene and hydrogen at the temperature of 650 °C. Plasma powers ranging from zero to 35 W were applied on the samples and the effects of different magnitudes of the plasma power on the growth direction of the CNTs were investigated. Regular vertically aligned nanotubes were obtained at plasma power of 25 W. In order to set on the plasma during the growth, electrical force was applied on the carbon ions. Nickel layer was used as a catalyst, and prior to the nanotubes growth step, it was treated by hydrogen plasma bombardment in order to obtain the Ni nano-islands. In this step, as the plasma power on the Ni layer was increased, the grain size of nickel nano-particles decreased, and hence, nanotubes of smaller diameter were obtained later on. At the last step some anomalous structures of agglomerated CNTs were obtained by controlling the plasma power. Samples were analyzed by scanning tunneling microscopy (STM) and scanning electron microscopy (SEM).

Photodiodes with a p-ZnO/oxide/n-Si substrate structure were fabricated. The N-In codoped p-type ZnO films were deposited by ultrasonic spray pyrolysis on a (111)-oriented silicon substrate with a thin oxide layer. A photocurrent of ~ 4.99 × 10-5 A was measured at a reverse bias of 1 V, and a photocurrent to dark current contrast ratio of almost five orders of magnitude was found. The photodiode responses exhibited three regions of behaviour: around 400 nm, between 400 nm–700 nm, and between 700 nm–1000 nm, denoted as regions A, B, and C, respectively. Region A corresponds to band-to-band absorption in the ZnO film, region B to band-to-deep level absorption in the ZnO film, and region C to band edge absorption in the Si substrate.