The morphology of submicronsized core-shell latex particles: an electron microscopy study

The core-shell structure of a range of acrylic-acrylic latexes has been investigated by combining different specimen preparation methods with transmission electron microscopy (TEM), dark-field scanning transmission electron microscopy (DSTEM) and low-voltage scanning electron microscopy (LV-SEM), including the first reported use of LV-SEM to observe composite latex particles at ambient and subambient temperatures. Spin-coating of liquid latex dispersions directly onto TEM grids or SEM stubs is shown to be a relatively straightforward mean of avoiding film formation during specimen preparation. In conjunction with double staining techniques, it has been found to be particularly convenient for characterizing the fine structure of particles with diameters down to below 100 nm.     

Polymorphs of the Gadolinite-Type Borates ZrB2O5 and HfB2O5 Under Extreme Pressure

Based on the results from previous high-pressure experiments on the gadolinite-type mineral datolite, CaBSiO₄(OH), the behavior of the isostructural borates β-HfB₂O₅ and β-ZrB₂O₅ have been studied by synchrotron-based in situ high-pressure single-crystal X-ray diffraction experiments. On compression to 120 GPa, both borate layer-structures are preserved. Additionally, at ≈114 GPa, the formation of a second phase can be observed in both compounds. The new high-pressure modification γ-ZrB₂O₅ features a rearrangement of the corner-sharing BO₄ tetrahedra, while still maintaining the four- and eight-membered rings. The new phase γ-HfB₂O₅ contains ten-membered rings including the rare structural motif of edge-sharing BO₄ tetrahedra with exceptionally short B−O and B⋅⋅⋅B distances. For both structures, unusually high coordination numbers are found for the transition metal cations, with ninefold coordinated Hf⁴⁺, and tenfold coordinated Zr⁴⁺, respectively. These findings remarkably show the potential of cold compression as a low-energy pathway to discover metastable structures that exhibit new coordinations and structural motifs.     

Copper Incorporation in ZnO during LP-MOCVD

The MOCVD of ZnO layers, at a reduced reactor pressure and using DMZ.2THF and tertiary butanol as zinc and oxygen sources, resp., presents a number of advantages compared with the deposition at normal pressure. This also applies to the copper incorporation by means of cyclopentadienyl-copper(I)-triethyl phosphine. For the copper concentration in the ZnO layers, which linearly increases with the flow rate of the organocopper compound, values > 10²⁰ cm⁻³ can be achieved. Even in case of high concentrations, the desired compensating effect of the copper is, for the time being, comparatively little, but increases considerably after a thermal retreatment of the layers. Some chemical-defect aspects of ZnO will be discussed for the purpose of interpretation.     

Functionalized N‐Aryl‐Substituted Cyclens by Nucleophilic Aromatic Substitution

The reaction of trifold protected cyclen with fluorinated dinitroarenes yields aryl‐substituted or aryl‐bridged cyclen derivatives in good yield. The two arene nitro groups, necessary for the nucleophilic aromatic substitution, are subsequently selectively reduced to amines and further functionalized by amide formation. As an example, a cyclen derivative bearing a heterocyclic oligoamide with potential DNA binding ability was prepared.     

Lattice dynamics of Eu<Subscript>1-x</Subscript>Y<Subscript>x</Subscript>MnO<Subscript>3</Subscript> (0 ≤ x ≤ 0.5)

A systematic and detailed study of Raman and infrared active lattice excitations in the orthorhombic multiferroic manganite Eu_1−xY_xMnO₃ (0 ≤ x ≤ 0.5) was carried out at room temperature. For the infrared active phonon modes the eigenfrequencies, damping constants and oscillator strengths were analyzed by Fourier-Transform Infrared Spectroscopy in the far infrared frequency range. For the Raman active phonons the same analysis for eigenfrequencies and damping constants was carried out using Raman spectroscopy in the range from 200 cm⁻¹ to 700 cm⁻¹. Y doping leads to mode-dependent phonon frequency shifts up to 8%. These are interpreted in terms of the interplay between the decrease of the reduced ion masses and the axis-dependent change of bond lengths. The latter leads to a bond softening along the a-axis and a strengthening along the c-axis, for which the highest phonon frequency increase is observed. The application of both Raman and Infrared Spectroscopy gives us sensitivity not only to symmetry properties via the selection rules but also to the involvement of different ion types within the unit cell. It is clearly shown that the disorder induced effects are of minor impact on the lattice properties and solely detected on the rare earth sites. The MnO₆ octahedra remain unaffected and show the same behavior as in the stochiometric RMnO₃ making Eu_1−xY_xMnO₃ an excellent model system for a quasi-continuous fine-tuning of the lattice parameters relevant for the appearance of multiferroicity.     

Lithography potentials of UV-nanoimprint

In the past decade nanoimprint has been developed to a serious alternative for next generation lithography (NGL). In this work, the most recent developments of UV-nanoimprint Lithography (UV-NIL) with special emphasis to the work accomplished at AMO and the IHT-RWTH Aachen are reviewed and functional applications demonstrated. Further the potentials of various UV-NIL concepts are evaluated and possible interests in certain application areas are discussed.     

The effect of a surface energy term on the distribution of phases in an elastic medium with a two‐well elastic potential

We consider the problem of minimizing among functions u:?^d?Ω→?^d, u_∣?Ω=0, and measurable subsets E of Ω. Here f_h⁺, f^? denote quadratic potentials defined on Ω¯×{symmetric d×d matrices}, h is the minimum energy of f_h⁺ and ε(u) is the symmetric gradient of the displacement field u. An equilibrium state û, Ê of J(u,E) is called one‐phase if E=?? or E=Ω, two‐phase otherwise. For two‐phase states, σ∣?E∩Ω∣ measures the effect of the separating surface, and we investigate the way in which the distribution of phases is affected by the choice of the parameters h??, σ>0. Additional results concern the smoothness of two‐phase equilibrium states and the behaviour of inf J(u,E) in the limit σ↓0. Moreover, we discuss the case of additional volume force potentials, and extend the previous results to non‐zero boundary values. Copyright © 2002 John Wiley & Sons, Ltd.