Determination of equilibrium composition of C x H y O z N t plasmas out of thermodynamic equilibrium

In this paper, we determine the composition of C_xH_yO_zN_t plasmas out of thermodynamic equilibrium using a more rigorous thermodynamic derivation of the Saha equation modified to two-temperature plasma system proposed by Chen et al. The calculation is made for these plasmas in pressure range 0.1-1 MPa and for electron temperature range 5 000-30 000 K. A great attention is given to the evolution of the major species such as hydrogen components (H, H₂), carbon monoxide (CO) and electrons. We compared the results obtained with our previous experimental and theoretical studies; the latter one has been carried out in equilibrium situation. We also compared our results with those given by the method based on the minimization of the Gibbs free energy widely used in the literature. Received 29 December 2000 and Received in final form 28 August 2001     

Preparation,stoichiometry and magnetic properties of Cu y Cr2Se4−z Br x spinels with 0.5≲x≲2

The chemical composition of Cu _y Cr₂Se_4?z Br _x spinels depends strongly on the preparation parameters. Spinels with 0.8?y?1.2, 0.5?x?2, and 0?z?x?0.2 have been prepared. Whereas the lattice constanta _o of these spinels differs only by less than approximately 0.6%, their Curie temperatureT _c depends sensitively on the spinel composition. For Cu_1.1Cr₂Se_3.4Br_o.46,a _o=1.0410 nm andT _c=310 K were found to compared witha ₀=1.0447 nm andT _c=84 K of CuCr₂Se₂Br₂.     

The XPS valence band spectra of Hf metal and HfC x N y O z compounds and the correlation to their superconductivity

The x-ray photoemission spectra of the valence bands of Hf metal and of several HfC _x N _y O _z compounds have been measured and are compared to existing band structure calculations. The density of states at the Fermi energy of the HfC _x N _y O _z compounds correlates strongly to their superconducting transition temperatureT _c . A calculation of theT _c values within the frame work of strong coupling superconductors indicates that the phonon spectrum and the electron phonon interaction is approximately constant within the series HfC _x N _y O _z .     

Mössbauer studies of ɛ-Fe3−x Ni x N and γ′-Fe4−y Ni y N nanoparticles

Nanocrystalline ?-Fe_3?x Ni _x N (0.0?≤?×?≤?0.8) particles are synthesized by precursor technique and nitridation of decomposed products in NH₃ (g) in the temperature range 673 K-823 K. For x?=?0.1–0.4 compositions, single phase ?-Fe_3?x Ni _x N hexagonal structure with space group P6₃/mmc is formed, while for x?=?0.5–0.8, fcc γ′-Fe_4?y Ni _y N phase is also precipitated. The room temperature Mössbauer spectrum for all the compositions shows the presence of superparamagnetic doublet, which is attributed to ?-Fe_3?x Ni _x N phase. For x?=?0.5–0.8 compositions, two additional sextets are observed corresponding to two different iron sites, the corner position (Fe^c) and the fcc position (Fe^f), in γ′-Fe_4?y Ni _y N. The added Ni atoms preferentially substitute the corner Fe^c positions. The isomer shift, quadrupole splitting and hyperfine field values are found to change with the Ni content.     

Lattice parameter and optical-energy gap values for Cd x Zn y Mn z Te alloys

Summary Polycrystalline samples of Cd _x Zn _y Mn _z Te alloys (x+y+z=1) were produced by a melt and anneal technique, by annealing at 800°C for 2 weeks giving good equilibrium conditions. Debye-Scherrer X-ray powder photographs were used to determine values of the lattice parametera and the range of solid solution in the zincblende phase. The range of solid solution determined is in good agreement with the previous values for the pseudobinary systems Cd_1−x Mn _z Te and Zn_1−z Mn _z Te. Room temperature measurements of optical absorption and modulated reflectance were made to give values of the energy gapE ₀ as functions of composition. The variation of the parametersa andE ₀ with composition is fitted to a suitable empirical equation, the accuracy of fitting was better than the average experimental scatter. From the fitted parameters, contours of constanta and of constantE ₀ were drawn. Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982.     

Informational incompleteness of the observablesS x,S y,S z for spin-1 systems

By a counter-example, we show that the set of the three spin components S_x, S_y, S_z of spin-1 systems is not informationally complete.     

Structural studies and T c dependence in La2−x Dy x Ca y Ba2Cu4+y O z type mixed oxide superconductors

A new series of mixed oxide superconductors with the stoichiometric composition La_2−x Dy _x Ca _y Ba₂Cu_4+y O _z (x=0.0 − 0.5, y=2x) has been studied for structural and superconductiong properties. Our earlier studies on La_2−x (Y/Er) _x Ca _y Ba₂Cu_4+y O _z series, show a strong dependence of T _c on hole concentration (p _sh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on x=0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant displacement of La onto Ba site. Superconductivity studies show that maximum T _c is obtained for x=0.5, y=1.0 sample (T _c ∼ 75 K), for La_1.5Dy_0.5Ca₁Ba₂Cu₅O _z (La-2125).     

Ascertaining the values of sigma x,sigma y,and sigma z of a polarization qubit

In the 1987 spin-retrodiction puzzle of Vaidman, Aharonov, and Albert one is challenged to ascertain the values of sigma(x), sigma(y), and sigma(z) of a spin-1/2 particle by utilizing entanglement. We report the experimental realization of a quantum-optical version in which the outcome of an intermediate polarization projection is inferred by exploiting single-photon two-qubit quantum gates. The experimental success probability is consistently above the 90.2% threshold of the optimal one-qubit strategy, with an average success probability of 95.6%.     

Optical properties of arachidate monolayers by integrated optical techniques

The refractive indices of thin dielectric films on the surface of an optical waveguide were determined from the mode patterns, i.e., effective indices in the guide as a function of selected visible laser wavelengths. These more accurate results are compared with previous measurements and illustrate the advantages of this method.     

Optical properties of laser-processed In x Ga1−x As

Various spots in GaAs, In-diffused with the 1.064 μm line of pulsed Nd:YAG laser with several energy densities, have been characterized and compared with samples prepared by the conventional rapid thermal annealing method. Of the energy densities used, the spot processed with an energy density of 7 J/cm² shows In _x Ga_1?x As phases with an indium concentration of 60% and below. An abrupt boundary in the indium concentration is observed at the edge of the laser-annealed spot. The diffusion depth is found to be less than 1000 Å. The spot processed with an energy density of 14 J/cm² shows considerable damage from the irradiation resulting in strain in the lattice. The samples prepared by the thermal annealing method show similar results to the laser-diffused samples. However, these thermally annealed samples suffer from arsenic loss unlike the laser-processed samples. It can be concluded that laser-induced alloying of indium into GaAs can be achieved with less arsenic loss than the thermal annealing method.     

The Effect of Water Vapor on the Conductivity and Emission Properties of the Formed Mo–Si x N y O z –Al Structure

The effect of water-vapor partial pressure on the conductivity and emission properties of the formed Mo–Si _x N _y O _z –Al sandwich-structure with a 40-nm thick dielectric and a 15-nm thick aluminium electrodes is studied. It is shown that an inflow of water-vapor into a degassed vacuum chamber results in the occurrence of a region of negative differential resistance in the volt-ampere characteristic and an increase in emission current in MIM-structures. The increase in conductivity is attributable to the formation of a delocalized impurity state band in local regions of dielectric surface due to water molecule adsorption.     

Optical and photoelectrical properties of glassy GeS x

Absorption edge, index of refraction, density and spectral dependence of the photoconductivity were measured on amorphous layers of stoichiometric GeS and on glasses GeS _x (1<x<2). An attempt is made to estimate the product of the mobility, lifetime and quantum efficiency for=0·9 m and=1·54 Å.Presented in part at the Int. Conf. on High Resistence Semiconductors, Photoelectrets and Electrophotography, Varna, Bulgaria, November 1973.Authors acknowledge valuable discussions with drs S.Koc and B.Velický, as well as the help of dr. J.Drahokoupil with the X-ray experiments. The glassy samples were kindly prepared by ing. A.Hrubý.     

Mössbauer studies in amorphous Fe80−x−y Ni x Mn y B12Si8 alloys

Room temperature Mössbauer studies have been carried out on amorphous Fe_80?x?y Ni _x Mn _y B₁₂Si₈ (x=35, 40, 45, 50 and 0≤y≤1). Thex=40 and 45 samples, showed an increase in the average hyperfine field, wheny increased from 0.0 to 0.2 at% in the former and 0.0 to 0.5 at% in the latter. The hyperfine field decreased fory=1.0. This is similar to the results of the magnetic moment on these samples, published earlier.     

Optical properties of gold electrode surfaces covered with metal monolayers

The relative reflectivity changes ΔR/R of a gold electrode surface caused by the deposition of monolayers of thallium, copper and lead from electrolytic solutions at underpotentials have been studied in situ in the photon energy range between 1.8 and 5.2 eV. The optical constants of the surface layer giving rise to this measured reflectivity change have been calculated and compared to the results of the electroreflectance effect on bare gold surfaces. It is shown that the reflectance change observed during the monolayer deposition is to first order due to a change in the gold electrode surface layer and not to absorption processes in the monolayer itself. The latter ones cause a fine structure superimposed to the substrate spectrum. The relatively strong change in the gold surface optical constants upon metal monolayer deposition is explained in terms of an enhanced electroreflectance effect due to the partially ionic character of the metal adatoms, which alters the free electron concentration in the substrate surface layer. Electroreflectance spectra obtained on gold surfaces covered with a monolayer of thallium compare favourably with dielectric loss functions computed for charged gold surfaces. This supports the assumption that the reflectivity changes observed upon metal monolayer deposition are mostly due to changes in the optical properties of the substrate metal surface.     

Optical properties of thiol terminated biphenyloxazole ordered monolayers on gold surface

New thiol terminated biphenyloxazole molecules are synthesized. A self assembled monolayer has been prepared on gold surface and spectral and luminescent properties of free molecules and ordered films have been studied experimentally and theoretically (DFT). The luminescence polarization degree is about 40%. New absorption and luminescence bands have been found experimentally and confirmed theoretically. The highest occupied and the lowest unoccupied molecular orbitals of adsorbed molecules strongly differ from not adsorbed thiol molecules.     

New improvements in energy and spatial (x,y, z) resolution in AES and XPS applications

This review presents the recent developments published in the literature about the use of Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) at high energy or spatial resolution. The past and present improvements due to technology (analysers, excitation source), and to mathematical procedures are described and discussed. New trends in the application of AES and XPS are related.