Derivation of the near-surface dielectric function of amorphous silicon from photoelectron loss spectra

The near-surface dielectric function ε(?ω) of hydrogenated amorphous silicon (a-Si:H) films has been derived from X-ray photoelectron energy-loss spectra, over the energy range 0–40 eV. Removal of low lying single-electron excitations is a prerequisite step to proceed to the derivation of the single plasmon energy loss function Im[? 1/ε(?ω)] due to collective electron oscillations. Several methods are compared to separate interband transitions from bulk or surface plasmons excitation. The shape of interband excitation loss in the range 1–10 eV can be described by a Henke function; alternatively, its removal using a sigmoid weighting function is a low-noise and reliable method. After deconvolution of multiple plasmon losses and self-consistent elimination of surface plasmon excitation, the single plasmon loss distribution allows recovery of optical (ellipsometry) data measured in the near-UV to visible range.     

The crystal and molecular structure of dichloro-(bis-1,2-diphenylphosphinoethane)platinum(II)

Crystals of PtCl₂(PPh₂)(CH₂)₂(PPh₂) (1), produced from attempts to prepare hydridochloroplatinum complexes, are monoclinic, space groupP2 ₁ /c, with four molecules in a unit cell of dimensionsa=11.478(3),b=13.263(2)c=16.343(3) Å, and =99.00(2)°. The structure was solved by the heavy-atom method and refined by block-diagonal least-squares calculations with anisotropicthermal parameters;R=0.048 andR=0.061 for 1843 observed reflections. The crystal structure contains discrete well-resolved molecules. The Pt atom has distorted square-planar coordination with Pt-P 2.208(6), Pt-Cl 2.355 and 2.341(6) Å distances, and Cl-Pt-Cl 90.2(2) and P-Pt-P 86.3(2)° angles.     

Electrical Characteristics of an Aluminum: Trans- (Ch)X Photodiode and Possible Defect-Related Current Transport

We have measured the electrical characteristics of photodiodes made by vacuum deposition of aluminum onto fibrous trans-(CH)_x. The trans-(CH)_x was not intentionally doped. The polymer surface was rough, so the Al overlayers were irregular. They were thick, to have low resistance, and had gaps that allowed some light into the junction. A simple equivalent circuit was fitted to the dark and illuminated current-voltage characteristics. The room temperature diode quality factor, n, was 1.9 for the junction in this circuit. This result is consistent with several mechanisms for the forward diode current, including that of charge carrier recombination at defects in the junction space charge region of the trans-(CH)_x.     

Crystal structure of (4α,4aα,8aα)-(±)-octahydro-2-(phenylmethyl)-2H-1,2-benzoxazin-4-ol, 4-methylbenzenesulfonate(ester)

The title compound, a bicyclic tetrahydro-1,2-oxazine, crystallizes in a monoclinic lattice, space group P2₁/c, with a = 12.9809(18)Å, b = 12.920(2)Å, c = 13.631(2)Å, = 110.713(12)°, and Z = 4. The structure found in the solid state for this conformationally mobile molecule shows the tosyl group in an axial position and a benzyl group in an equatorial position of the bicyclic system.     

Crystal structures of (η5-C5H4COMe)M(CO)3Me (M=Mo,W)

The crystal structures of ( ⁵-C₅H₄COMe)M(CO)₃Me (M=Mo,W) have been determined. They are not isostructural. M=Mo isP2₁/c,a=10.205(6),b=14.192(8),c=8.135(6) Å,=93.43(4)° andD(calc)=1.71 g cm^–3 forZ=4. M=WisP2₁/c,a=12.580(7),b=6.830(5),c=13.750(7) Å,=93.72(4)° andD(calc)=2.20 g cm^–3 forZ=4. Both have a four-legged piano stool geometry with the substituted carbon making the closest M-C( ⁵) approach. The methyl group in the M=W derivative is disordered between twotrans-ligand positions. The average bonding parameters for the more accurately determined Mo analog are: Mo-C()⁵)=2.34(3) Å, Mo-CO=1.98(2) Å, Mo-Me=2.304(4) Å.     

Bi incorporation in GaAs(100)-2×1 and 4×3 reconstructions investigated by RHEED and STM

Bi acts as a surfactant in molecular beam epitaxy (MBE) growth on GaAs(100). Incorporation is achieved by disequilibrium at growth temperatures below ～450 °C. Bi can however affect the static reconstruction up to 600 °C. Two reconstructions are considered in this work: dynamic (2×1) and static c(8×3)/(4×3), which are shown to be the dominant reconstructions for GaAsBi MBE. Bi storage in these two reconstructions provides an explanation of RHEED transitions that cause unintentional Bi incorporation in the GaAs capping layer. Finally dynamic observations of the (2×1) reconstruction are used to explain growth dynamics, atomic ordering and clustering observed in GaAsBi epilayers which have a direct influence on photoluminescence linewidth broadening in mixed anion III–V alloys.     

Molecular structures of [CpRu(PPh3)(dtoxa-H2O)]BF4 and {[CpRu(PPh3)2]2(μ-dtoxa)}(BF4)2, dtoxa=dithiooxamide

The reaction of [CpRu(PPh₃)₂(n-C₃H₇SH)]BF₄ with dithiooxamide (dtoxa) gave two products: {[CpRu(PPh₃)₂]₂(-dtoxa)} (BF₄)₂,1, and [CpRu(PPh₃)(dtoxa-H₂O)]BF₄,2. The structures of both complexes were determined by X-ray diffraction techniques. Compound1 crystallized in the triclinic space groupP _¯1,a=12.822(4),b=14.16(1),c=23.631(8) Å,=84.57(4),=83.64(3), =83.57(4)°,Z=2,R=0.069,R _w =0.084. The structure of1 shows two CpRu(PPh₃)₂ ⁺ units bridged through the S atoms of the dtoxa ligand. Ru-S distances are 2.377(6)Å for Ru1-S1 and 2.368(6) Å for Ru2-S2. Compound2 crystallized in the monoclinic space groupP2₁/c,a=13.446(3),b=13.461(7),c=31.214(7) Å,=100.78(3)°,Z=8,R=0.054,R _w =0.055. The structure of2 has two molecules in the asymmetric unit. The Ru is chelated to the dtoxa through the S atoms: Ru1-S1, 2.307(4); Ru1-S2, 2.300(4); Ru2-S3, 2.295(4); Ru2-S4, 2.287(4) Å. The coordination sphere of the Ru in2 is completed by a cyclopentadienyl ligand and a triphenylphosphine.     

Preparation and X-ray crystal structures of mixed ligand complexes containing the S3N ligand

Reaction of Hg(S₇N)₂ with cis- PtCl₂(PR₃)₂ (PR₃ = PPh₃, PPh₂Me, PPHMe₂, PEt₃) in the presence of Na[PF₆] gives [Pt(S₃N)(PR₃)₂][PF₆] in 32–46% yield. The complexes have been characterized by IR, NMR and microanalyses. The X-ray crystal structures of two examples (PR₃ = PPh₂Me and PEt₃) show that the S₃N⁻ ligand coordinates in a bidentate fashion via two sulphur atoms.     

Fixed-nuclei and laboratory-frame formalisms for electron scattering by a spherical top,with full incorporation of symmetry

We discuss molecule-frame and laboratory-frame symmetry-adapted formalisms for electron scattering by a spherical top. The molecule-frame formalism is based on the fixed-nuclear-orientation approximation, both for electronically elastic scattering by a vibrationally rigid molecule and also for the more general case where electronic excitation and vibrational degrees of freedom are included. The laboratory-frame formalism is based on the exact symmetries of the problem, which are carefully related to the approximate symmetries of the molecule-frame treatment. We present both the forward and backward transformations between the two representations.