IR photodetectors based on GaAs/Al0.25Ga0.75As multiquantum wells (QWIP) grown by molecular beam epitaxy (MBE) are studied. The envelop function formalism is used to determine the theoretical intersubband transition energies. The electronic states are calculated in both parabolic and non parabolic cases. IR spectroscopy transmission is used as the experimental technique to evaluate the optical absorption. The measures are made at 77 K for incidence at both 45° and Brewster angles geometries. The last experimental results compare well with the theoretical ones and correspond to 10–12  $\mu $ m operating wavelength.

( $1-x$ )Pb(Fe0.5Nb0.5)O3-xPb(Zr0.2Ti0.8)O3 (PFN-PZT, x = 0.75, 0.80, 0.85) ferroelectric ceramics were prepared by conventional solid-state reaction method via the wolframite precursor route. XRD measurements confirmed that the synthesized PFN-PZT ceramics are of pure tetragonal perovskite structure. With the increase of Pb(Zr0.2Ti0.8)O3 (PZT) content, tetragonality (defined as the ratio of cell parameter c/a) increases slightly accompanied by the variation of cell volume. At the optimized sintering condition of 1175 °C for 2 h, the 0.20PFN-0.80PZT ceramics exhibit the largest value of relative density (93.77%). The PFN-PZT ceramics exhibit first-order ferroelectric phase transition of typical normal ferroelectrics, where the dielectric response peaks are narrow, sharp and without frequency dispersion, and the dielectric constant above Curie temperature (T C ) can be fitted well by Curie law. The sintered PFN-PZT ceramics exhibit high-T C , and with the increase of PZT content, T C increases and reaches 368, 394 and 401 °C, respectively. With the increase of PZT content, the P-E ferroelectric hysteresis loops of the PFN-PZT ceramics become narrower accompanied by the decrease of remanent polarization (P r ) and coercive field (E C ). Piezoelectric constant d 33 of all the PFN-PZT ceramics is small, less than 10 pC/N.

Dy-doped CdO films were prepared and post-annealed in hydrogen atmosphere for different durations (15 min, 30 min and 45 min). They were characterised by measuring their structural, electrical, and optical properties. The results indicate that annealing in H2 gas does not change the crystalline CdO structure of the films. The electrical behaviours of Dy-doped CdO films show that they are degenerate semiconductors with bandgap 1.75 eV. The bandgap of the hydrogenated Dy-doped CdO films changes with H2-annealing time following the changing in the carrier concentration. These results were found to be in agreement with the available models for bandgap widening and bandgap narrowing. The Dy-doping of CdO films enhances their electrical conduction. An additional enhancement was obtained with pre-annealing in H2 gas so that the greatest enhancement occurs with annealing for 30 min. when the conductivity increased by about 40% and the free-electrons concentration increased by about 260% relative to the non-hydrogenated CdO:Dy film. From transparent-conducting-oxide point of view, Dy is sufficiently effective for CdO doping especially when including a pre-annealing in H2 atmosphere.   

The preparation and properties of CdTe thin films is of a primary interest for the CdTe thin film solar cells in both research and technology. In our work, polycrystalline CdTe thin films were deposited on pretreated glass substrates in Ar/O2 atmosphere by closed-space sublimation (CSS) technology. Structural property was studied by X-ray diffraction (XRD), surface morphology was observed by scanning electron microscopy (SEM). The optical and electrical properties of CdTe films were investigated, as well as the effects of deposition temperatures, the ratio of gas (Ar/O2) and post-treatment on the properties. The high quality CdTe layer was prepared based on the above studies. These layers were used to prepared CdS/CdTe/ZnTe:Cu solar cells. Efficiency of 13.38% and fill factor of 70.3% (0.501 cm2 area) for CdTe solar cells have been achieved.

We report the growth of indium-rich InGaN alloys by metal-organic vapour phase epitaxy, using ammonia, trimethylgallium and trimethylindium as precursors. Compared to indium nitride, our alloy samples present substantial photoluminescence robustness with temperature. The analysis of the optical properties of these samples versus temperature indicates the existence of two non radiative recombination channels: one with a thermal activation temperature of 77 K and another one with an activation temperature ranging from 300 K for InN up to 640 K for In0.72Ga0.28N. The latter competes with the former at low temperatures whilst the former rules the optical properties at ambient conditions.

In this paper we report the nano-phase separation structure in the polymer blend film and its optical properties. Polystyrene (PS)/polymethyl methacrylate (PMMA) blend film is spin-coated on substrate. A sandwiched structure consisting of a depleted PMMA layer, a PS/PMMA blend layer and a PS-rich top layer has been formed. By selectively dissolving the PS-rich phase, a nanoporous film is generated, and the nanoporous structure can be tuned by changing the weight ratio of PS/PMMA in the blend solution in fabrication. The optical properties of the nanoporous thin films are determined. Our results show that by introducing the nanoporous structure, the refractive index can be effectively modified. By selecting proper film thickness, the maximum optical transmission can be achieved in the specific waveband.

Using electron-induced X-ray emission spectroscopy (XES), we have studied two Al/Ni periodic multilayers that differ only by their annealing temperature: as-deposited and annealed at 115 °C. Our aim is to show that XES can provide further details about the chemistry at the metal-metal interface, in addition to what is obtained by X-ray diffraction. The distribution of valence states exhibiting Al 3p and Ni 3d character is determined from the analysis of the Al $K\beta$ and Ni $L\alpha$ emission bands respectively. The multilayer emission bands are compared to those of reference materials: pure Al and Ni metals as well as Al3Ni, Al3Ni2 and AlNi intermetallics. We provide evidence that, for temperatures up to 115 °C, Al3Ni is the major component of the multilayer.

Kidney stones consist of various organic, inorganic and semi-organic compounds. Mineral oxalate monohydrate and di-hydrate is the main inorganic constituent of kidney stones. However, the mechanisms for the formation of crystal mineral oxalate are not clearly understood. In this field of study there are many hypothesis including nucleation, crystal growth and or aggregation of formation of AOMH (ammonium oxalate monohydrate) and AODH (ammonium oxalate di-hydrate) crystals. The effect of some urinary species such as ammonium oxalates, calcium, citrate, proteins and trace mineral elements have been previously reported by the author. The kidney stone constituents are grown in the kidney environments, the sodium meta silica gel medium (SMS) provides the necessary growth simulation (in vitro). In the artificial urinary stone growth process, growth parameters within the different chemical environments are identified. The author has reported the growth of urinary crystals such as CHP, SHP, BHP and AHP. In the present study, BaNH4MgHPO4 (barium ammonium magnesium hydrogen phosphate) crystals have been grown in three different growth faces to attain the total nucleation reductions. As an extension of this research, many characterization studies have been carried out and the results are reported.

This paper displays some simulation results of dynamic responses of the high-T c superconductors (HTSC)-Permanent magnet (PM) levitation systems taking into account the influence of the flux creep phenomena and of the thermal effect. We focus on the establishment of a three-dimensional numerical code to solve the nonlinear and coupled equations. A new control volume method is proposed for the resolution of the partial derivative equations of the treaded physical phenomena. The influence is comprehensively displayed by comparing the predictions of dynamic responses of such systems in which the thermal effect in the superconductor is and is not taken into account. The electromagnetic and thermal coupling is ensured by an alternate algorithm. The thermal effect highlights the influence of the temperature on the value of the magnetic levitation force, levitation stabilization time and shows that the vibration center of levitated body had drifted downward.

The dynamics of gas heating in fast pulsed discharges in nitrogen-oxygen mixtures was analyzed using a state-specific plasmachemical model and an energy conservation equation. It was shown that the heating rate changes over time according to the changes of the species involved in the heating processes. An increasing dependence on time was shown. The results show that higher electron density, electric field or partial pressure of oxygen leads to a faster gas heating. However, the heating rate associated with excitation of vibrational and electronic degrees of freedom is almost independent of the value of the applied field in the studied range of fields.

We demonstrate a simple approach for a difference-frequency synthesiser within the terahertz domain. Two near-infrared CW diode lasers are frequency-locked to the resonances of a high finesse Fabry-Perot cavity using the Pound-Drever-Hall technique. Two acousto-optic modulators driven by RF synthesizers frequency-shift each diode laser and provide continuous tuning, modulation and switching capabilities for the difference-frequency. Terahertz-waves generated by heterodyne mixing in an ultrahigh-bandwidth photodetector are used to interrogate the rotational transitions in the ground state of themethyl-chloride.

We describe a method and present the results of the measurements ofspectral change of stored ultra-cold neutrons and the sub-barrier neutronup-scattering from solid surfaces to the energy range higher than theboundary energy of the sample. The method consists in measuring the neutron absorption curvesas a function of UCN storage time and the thickness of the absorbers. The quasi-elastic and inelastic UCN up-scattering probability is determinedat room temperature. The neutron spectra are inferred in monochromatic and more detailedapproximations.