Application of Information Statistical Theory to the Description of the Effect of Heat Conduction on the Chemical Reaction Rate in Gases

The effect of the heat flux on the rate of chemical reaction in dilute gases is shown to be important for reactions characterized by high activation energies and in the presence of very large temperature gradients. This effect, obtained from the second-order terms in the distribution function (similar to those obtained in the Burnett approximation to the solution of the Boltzmann equation), is derived on the basis of information theory. It is shown that the analytical results describing the effect are simpler if the kinetic definition for the nonequilibrium temperature is introduced than if the thermodynamic definition is introduced. The numerical results are nearly the same for both definitions

Spectroscopic ellipsometry study of the In1-x Gax Asy P1-y / InP Heterojunctions grown by metalorganic chemical-vapor deposition

The dielectric functions of InP, In0.53Ga0.47As, and In0.75Ga0.25As0.5P0.5 epitaxial layers have been measured using a polarization modulation spectroscopic ellipsometer in the 1.5 to 5.3 eV region. The oxide removal procedure has been carefully checked by comparing spectroscopic ellipsometry and x ray photoelectron spectroscopy measurements. These reference data have been used to investigate the structural nature of metalorganic chemical vapor deposition grown In0.53Ga0.47As/InP and In0.75Ga0.25As0.5P0.5/InP heterojunctions, currently used for photodiodes and laser diodes. The sharpness of the interfaces has been systematically compared for the two types of heterojunctions: In1 xGaxAsy/InP and InP/In1 xGaxAsyP1 y. The sharpest interface is obtained for InP growth on In0.75Ga0.25As0.5P0.5 where the interface region is estimated to be (10±10) Å thick. The importance of performing in situ SE measurements is emphasized.

Alteration and Contamination of Archaeological Ceramics: the Perturbation Problem

Alteration and contamination processes modify the chemical composition of ceramic artefacts. This is not restricted solely to the affected elements, but also affects general concentrations. This is due to the compositional nature of chemical data, enclosed by the restriction of unit sum. Since it is impossible to know prior to data treatment whether the original compositions have been changed by such processes, the methodological approach used in provenance studies must be robust enough to handle materials that might have been altered or contaminated. The ability of the logratio transformation proposed by Aitchison to handle compositional data is studied and compared with that of present data treatments. The logaratio transformation appears to offer the most robust approach

Optoelectronic studies in nanocrystalline silicon Schottky diodes obtained by Hot-Wire Chemical Vapour Deposition

The very usual columnar growth of nanocrystalline silicon leads to electronic transport anisotropies. Whereas electrical measurements with coplanar electrodes only provide information about the electronic transport parallel to the substrate, it is the transverse transport which determines the collection efficiency in thin film solar cells. Hence, Schottky diodes on transparent electrodes were obtained by hot-wire CVD in order to perform external quantum efficiency and surface photovoltage studies in sandwich configuration. These measurements allowed to calculate a transverse collection length, which must correlate with the photovoltaic performance of thin film solar cells. Furthermore, the density of charge trapped at localized states in the bandgap was estimated from the voltage dependence of the depletion capacitance of these rectifying contacts.