Ein fünffach koordinierter ionischer zirkonium(IV)-komplex mit der (π-C5H5)2ZrIV-Baueinheit: [(π-C5H5)2Zr(H2O)3]2+(CF3SO3−)2·THF

The ionic complex [(π-C₅H₅)₂Zr(H₂O)₃]²⁺(CF₃SO₃^?)₂·THF, which corresponds to the 18-electron rule, is formed in the reaction of (π-C₅H₅)₂Zr(CF₃SO₃)₂(THF) with H₂O in tetrahydrofuran. It crystallizes in the hexagonal space group P6₃ with Z = 6 and unit cell dimensions at ? 100°C of a 21.945(5) and c 8.711(3) Å. The geometry of the (π-C₅H₅)₂Zr moiety (length of the vectors between Zr and the C₅ ring centroids: 2.210 and 2.193 Å; angle between these vectors: 129.0°; angle between the C₅ ring normals: 128.3°) agrees with that of neutral, four-coordinate (π-C₅H₅)₂ZrX₂ compounds. The three H₂O ligands lie in the plane that bisects the angle between the C₅ ring planes. The ZrO distances are 2.239(7), 2.195(7), and 2.261(7) Å. The CF₃SO₃^? anions and the THF molecule of crystallization are packed around the complex cation in such a way that their oxygen atoms point towards the H₂O ligands. The CF₃ sides of the anion, on the other hand, are clustered together so as to produce hydrophobic domains in the crystal structure.     

Bis-μ-hydroxo-bis(π-cyclopentadienyldinitratozirkonium-(IV))tetrahydrofuran(12), ein zweikerniger organozirkonium(IV)-komplex mit siebenfach koordinierten metallzentren

Cp₂ZrCl₂ reacts with nitric acid in CHCl₃ to yield a dinuclear, doubly OH-bridged complex which can be isolated together with tetrahydrofuran of crystallization: [π-C₅H₅Zr(NO₃)₂(μ-OH)]₂ · 2THF (B). The crystal data of B are as follows: space group P2₁/c, a 8.825(2), b 12.137(3), c 13.018(2) Å, β 97.61(2)°. The unit cell contains two dinuclear centrosymmetric metal complexes and four molecules of tetrahydrofuran of crystallization. The Zr atom has a pentagonal-bipyramidal coordination geometry with the Cp group occupying an axial position, two chelating NO₃ ligands and one OH bridging group in the equatorial plane, and one OH group in the other axial position.     

Compositional investigation of potassium doped Cu(In,Ga)Se2 solar cells with efficiencies up to 20.8%

We report on the interaction between intentional potassium doping of thin film Cu(In,Ga)Se₂ (CIGS) solar cells, CIGS absorber composition, and device efficiency. Up to now high efficiency CIGS solar cells could not be produced with a gallium/(gallium + indium) ratio higher than 35%. The new doping process step does not only increase solar cell conversion efficiencies up to 20.8%, but also allows a shift in the CIGS absorber composition towards higher gallium content whilst maintaining this high efficiencies level. We find that the saturation of the open circuit voltages for higher gallium content that is normally observed can partially be overcome by the new doping procedure. This observation leads us to the conclusion that even on this high performance level CIGS solar cells still hold a potential for further development beyond the record values reported here. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase transition to the resonating valence bond state

A Ginzburg-Landau expansion for the free energy functional of the resonating valence bond state is performed for the mean field approximation (MFA) and for a functional integral approach (FIA) which includes correlations. Phase diagrams obtained in both approximations are presented. The FIA differs form the MFA in three main aspects: (i) Above the mean field transition temperature an instability exists towards the formation of degenerate singlet pair states, indicating the onset of the RVB state. (ii) The extendeds-wave phase is favoured over the extendedd-wave phase. (iii) Phase fluctuations are included, destroying off-diagonal order in the absence of holes.     

EPMA and Quantitative MCs+-SIMS of Metal-DLC Coating Materials

 Compositional characterization of metal-DLC (metal-containing diamond-like carbon) hard coatings is carried out by (WDS)-EPMA and MCs⁺-SIMS. EPMA enables accurate (± 5% relative) quantitative analysis including minor concentrations (0.1–10 at%) of N, O and Ar. Under conditions of “near-surface” EPMA (E₀ < 10 keV) the influence of surface oxide films on “pure” metal standards may be a limiting factor in respect of accuracy. Depth profiling of sufficiently “thick” layered structures (film thickness ≥ 2 μm) is carried out by EPMA-line scans along mechanically prepared bevels. The depth resolution is about 0.2 μm. SIMS in the MCs⁺-mode enables high resolution (< 20 nm) depth profiling of metal-DLC layered structures including the determination of H (1–20 at%). MCs⁺-SIMS, i.e. employing Cs⁺ primary ions and monitoring MCs⁺ molecular secondary ions (M is the element of interest) is presented as a promising route towards sufficiently accurate (10–20%) SIMS-quantification. Matrix-independent relative sensitivity factors for MCs⁺-SIMS are derived from homogeneous coating materials defined by EPMA. EPMA proves to be also useful to detect problems related to SIMS of Ar in metal-DLC materials. The combination EPMA-SIMS is demonstrated as an effective analytical strategy for quality control in industrial production and to support the development of metal DLC layered structures with optimum tribological properties.     

Lactone polymers. III. Polymerization of ε-caprolactone

Polymerization of ε-caprolactone catalyzed by dibutylzine and triisobutylaluminum has been examined. Monomer conversion and polymer molecular weight increase simultaneously during the polymerization suggesting a living polymer system. Also, molecular weight is proportional to the reciprocal of catalyst concentration. However, the polymer molecular weights are three to five times that which would be calculated from the catalyst concentration assuming a living polymer system. In addition, fractionation of poly-ε-caprolactone prepared with dibutylzinc revealed that the distribution is considerably broader than expected for a Poisson distribution. While no mechanistic explanation for the broad molecular weight distribution observed has been defined, examination of the metal alkyl-catalyzed polylactones shows that the molecular weight distributions can and do change with time. This change is due to an ester interchange process occurring subsequent to polymerization. This phenomenon can be used to change the molecular weight distribution from very broad to the most probable distribution.     

Hybrid polymer/silica thermo-optic vertical coupler switches

Thermo-optic 1×2 vertical coupler switches (VCSs) using a hybrid polymer/silica integration technology were designed using a finite element method and a coupled mode method for different refractive index contrasts. The multilayer structures were optimized by thermal analysis. Based on these designs and simulations, hybrid polymer/silica thermo-optic 1×2 VCSs exhibiting low insertion loss, low crosstalk, low switching power and polarisation independence were demonstrated. Based on this building block, a 1×8 VCS has been fabricated. Received: 21 May 2001 / Published online: 23 October 2001     

Level statistics and localization: A study of the 1D Anderson model

The level statistics and the localization of a particle in a one-dimensional random potential are investigated numerically. First, we study the level spacing distributionP(S) as a function of the system lengthN and of the disorderw of the system. We show that in addition to the localized and delocalized regimes a third regime can be distinguished: For large disorder a resonance appears inP(S), which is caused by a local level repulsion effect. Second, we investigate the distribution of the localization lengths within the Anderson chain as a function ofN andw. Here, we identify the localization length with the rms spread of the wave functions and we show that this measure for the localization of the eigenstates is not a self-averaging quantity.