Influence of substrate dopant type on the optical properties of GaInAs/InP multiquantum well structures grown by low pressure MOVPE

A correlation between substrate dopant type and the absorption spectra of MQW structures has been identified. Optical absorption spectra from MQW structures grown on S-doped InP can show poorly resolved excitonic features with respect to those obtained from structures grown on both Sn- and Fe-doped substrates. It is proposed that this degradation is due to enhanced interfacial diffusion on the Group V sublattice for structures grown on substrates incorporating low defect densities.     

Convergence of an s‐Wave calculation of the He ground state

The configuration interaction (CI) method using a large Laguerre basis restricted to ? = 0 orbitals is applied to the calculation of the He ground state. The maximum number of orbitals included was 60. The numerical evidence suggests that the energy converges as ΔE^N ≈ A/N^7/2 + B/N^8/2 + …, where N is the number of Laguerre basis functions. The electron–electron δ‐function expectation converges as Δδ^N ≈ A/N^5/2 + B/N^6/2 + …, and the variational limit for the ? = 0 basis is estimated as 0.1557637174(2) a. It was seen that extrapolation of the energy to the variational limit is dependent on the basis dimension at which the exponent in the Laguerre basis was optimized. In effect, it may be best to choose a nonoptimal exponent if one wishes to extrapolate to the variational limit. An investigation of the natural orbital asymptotics revealed the energy converged as ΔE^N ≈ A/N⁶ + B/N⁷ + …, while the electron–electron δ‐function expectation converged as Δδ^N ≈ A/N⁴ + B/N⁵ + …. The asymptotics of expectation values other than the energy showed fluctuations that depended on whether N was even or odd. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Negative differential resistance (NDR) in similar molecules with distinct redox behaviour

The transport characterization of self-assembled monolayers (SAMs) based on the closed and open-shell forms of a fully conjugated polychlorotrimethylphenyl (PTM) derivative hybridized with the gold substrate reveals that both systems exhibit negative differential resistance (NDR) in their I-V curves which was attributed to similar resonant tunnelling with unoccupied molecular orbitals. This work demonstrates that distinct transport mechanisms can dominate depending on the bias-voltage applied and shows that NDR processes are not influenced here by the redox character of the molecules.     

Chemical Factors That Influence the Production of Conductive and/or Reflective Silver-Doped Polyimide Films

ABSTRACT

Doping a poly(amide acid) resin with a silver containing additive (1,5-cyclooctadiene-hexafluoroacetylacetonato)-silver(I) [Ag(COD) (HFA)] resulted, after thermal cure, in either a highly reflective or highly eléctrically conductive polyimide film. The combination of monomers, which render films with low T_g (~210°C), and contained sulfur, produced films with surface resistance in the range 10^1–10³ ohms. On the other hand, films with specular reflectivity (relative to a silver mirror) in the range of 65–48% were obtained using both high T_g polyimides and polyimides void of sulfur in the polyimide backbone with low T_g. Our understanding regarding the structure-property relationship on these polyimide films and also the characterization of the doped-films are discussed.     

Synthesis and properties of stereoregular fluoro-polymers via ring-opening metathesis polymerization of fluorinated norbornenes and norbornadienes. An overview and progress report

Since the first report of the ring-opening metathesis polymerization of fluorinated monomers in 1979 considerable advances in precision and control of such syntheses have been achieved through the introduction of well defined initiators. It is now possible to carry out well controlled living and stereoregular polymerizations. The products of such syntheses can display unusually high relaxed dielectric constants, an observation which is crucial to the assignment of their tacticities and probably significant with regard to possible applications of this type of material.     

ChemInform Abstract: Density Functional Studies of Model Cerium Oxide Nanoparticles.

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