This work deals with the study of the role of intra-gap density of states and films composition on the colour selection of the collection spectrum of glass/ITO/a-Six:C1-x:H/Al Schottky photodiodes produced in a conventional plasma-enhanced chemical vapour deposition (PECVD) system using as gas sources silane and a controlled mixtures of silane and methane. To do so, properties of the films were investigated, especially the one concerning the determination of the valence controllability of the films produced and the density of bulk states. Besides that, a PINIP device was also produced, using the a-Six:C1-x:layer that lead to the best Schottky diode performances. © 2001 Elsevier Science B.V. All rights reserved.

The process conditions of growing thin silicon films by plasma enhanced chemical vapour deposition (PECVD) were presented. The plasma impedance was found to monitor the powders in the PECVD systems and good quality silicon films were grown close to the plasma regime where the powders were formed. The silicon films exhibited properties which were interpreted based on a two-phase model where silicon nanostructures were embedded in a disordered network.

We derive a theoretical expression for the two-photon emission rate of two-electron systems, in a form suitable for easy implementation in numerical calculations. Racah algebra techniques were used to extended previous work on two-photon emission in hydrogen-like systems to more complex ones. The obtained expression is, as far as we are aware, the first general expression that gives the spontaneous two-photon decay rates of helium-like systems for any combination of multipoles.

Ferrochelatase (EC 4.99.1.1) is the terminal enzyme of the haem biosynthetic pathway and catalyses iron chelation into the protoporphyrin IX ring. Glutamate-287 (E287) of murine mature ferrochelatase is a conserved residue in all known sequences of ferrochelatase, is present at the active site of the enzyme, as inferred from the Bacillus subtilis ferrochelatase three-dimensional structure, and is critical for enzyme activity. Substitution of E287 with either glutamine (Q) or alanine (A) yielded variants with lower enzymic activity than that of the wild-type ferrochelatase and with different absorption spectra from the wild-type enzyme. In contrast to the wild-type enzyme, the absorption spectra of the variants indicate that these enzymes, as purified, contain protoporphyrin IX. Identification and quantification of the porphyrin bound to the E287-directed variants indicate that approx. 80% of the total porphyrin corresponds to protoporphyrin IX. Significantly, rapid stopped-flow experiments of the E287A and E287Q Variants demonstrate that reaction with Zn2+ results in the formation of bound Zn-protoporphyrin IX, indicating that the endogenously bound protoporphyrin IX can be used as a substrate. Taken together, these findings suggest that the structural strain imposed by ferrochelatase on the porphyrin substrate as a critical step in the enzyme catalytic mechanism is also accomplished by the E287A and E287Q variants, but without the release of the product. Thus E287 in murine ferrochelatase appears to be critical For the catalytic process by controlling the release of the product.

The reaction between [Cu(NCMe)(4)][PF6] and 1,1'-bis-(diphenylphosphino)-ferrocene (dppf) in several ratios, solvents, and conditions led to the synthesis and structural characterization of the Cu(I) complexes [Cu(dppf)(Odppf)] [PF6] (1), [(dppf)Cu(mu -dppf)Cu(dppf)][PF6](2) (2), and [(dppf)Cu(mu -Cl)(2)Cu(dppf)] (3). Although 1 and the cation in 2 were known, the first was structurally characterized for the first time, exhibiting a significant asymmetry in the coordination sphere of Cu(I)) owing to the presence of oxygen. In 2, the PF6- anion led to an interesting crystal packing with large open channels containing water. Finally, DFT calculations on a model of 3 showed that its HOMO exhibits, besides Fe, a significant Cu and Cl character, which is reflected in its electrochemical properties.

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In this work we present a study performed in a plasma-enhanced chemical vapour deposition reactor, where different rf electrode configurations were used with the aim of achieving conditions that lead to growth of highly uniform amorphous silicon films, with the required electronic quality, at high growth rates. This study consists in determining the plasma characteristics under different electrode configurations, in an argon plasma, using as diagnostic tools a Langmuir probe and impedance probe. These results were correlated with the hydrogenated amorphous silicon films produced, thereby allowing us to establish the best electrode configuration to grow electronic-grade-quality amorphous silicon films.

Electronic procurement of partners is an important functionality during the life cycle of a virtual enterprise. A prototype implementation, featuring selection based on both internal or Internet-based suppliers’ directories, is discussed. The generation of call for tenders and support for management of received bids is introduced and directions for contract negotiation and decision support system are discussed.

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This paper is concerned with the modelling and simulation of amorphous and microcrystalline silicon optoelectronic devices. The physical model and its mathematical formulation are extensively described. Its numerical reduction is also discussed together with the presentation of a computer program dedicated to the simulation of the electrical behaviour of such devices. This computer program, called ASCA (Amorphous Silicon Solar Cells Analysis), is capable of simulating, on one- and two-dimensional domains, the internal electrical behaviour of multi-layer structures, homojunctions and heterojunctions under simple or complex spectra illumination and externally applied biases. The applications of the simulator presented in this work are the analysis of μc/a-Si:H p-i-n photovoltaic cell in thermal equilibrium and illuminated by monochromatic light and the AMI.5 solar spectrum, with and without polarisation. We also study the appearance within the device of lateral components of the electric field and current density vectors when the illumination is not uniform. © 1999 IMACS/Elsevier Science B.V. All rights reserved.