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Very Thin Films (very + thin_film)
Selected AbstractsApplication of a single-reflection collimating multilayer optic for X-ray diffraction experiments employing parallel-beam geometryJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2008M. Wohlschlögel Instrumental aberrations of a parallel-beam diffractometer equipped with a rotating anode X-ray source, a single-reflection collimating multilayer optic and a parallel-plate collimator in front of the detector have been investigated on the basis of standard measurements (i.e. employing stress- and texture-free isotropic powder specimens exhibiting small or negligible structural diffraction line broadening). It has been shown that a defocusing correction, which is a major instrumental aberration for diffraction patterns collected with divergent-beam (focusing) geometries, is unnecessary for this diffractometer. The performance of the diffractometer equipped with the single-reflection collimating multilayer optic (single-reflection mirror) is compared with the performance of the diffractometer equipped with a Kirkpatrick,Baez optic (cross-coupled Göbel mirror) on the basis of experimental standard measurements and ray-tracing calculations. The results indicate that the use of the single-reflection mirror provides a significant gain in photon flux and brilliance. A high photon flux, high brilliance and minimal divergence of the incident beam make the setup based on the single-reflection mirror particularly suitable for grazing-incidence diffraction, and thus for the investigation of very thin films (yielding low diffracted intensities) and of stress and texture (requiring the acquisition of large measured data sets, corresponding to the variation of the orientation of the diffraction vector with respect to the specimen frame of reference). A comparative discussion of primary optics which can be used to realise parallel-beam geometry shows the range of possible applications of parallel-beam diffractometers and indicates the virtues and disadvantages of the different optics. [source] The ,-particle excited scintillation response of YAG:Ce thin films grown by liquid phase epitaxyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2009Petr Prusa Abstract Y3Al5O12:Ce (YAG:Ce) thin films were grown from PbO-, BaO-, and MoO3 -based fluxes using the liquid phase epitaxy (LPE) method. Photoelectron yield, its time dependence within 0.5,10 ,s shaping time, and energy resolution of these samples were measured under ,-particle excitation. For comparison a sample of the Czochralski grown bulk YAG:Ce single crystal was measured as well. Photoelectron yield values of samples grown from the BaO-based flux were found superior to other LPE films and comparable with that of the bulk single crystal. The same is valid also for the time dependence of photoelectron yield. Obtained results are discussed taking into account the influence of the flux and technology used. Additionally, , particle energy deposition in very thin films is modelled and discussed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Heterocyclic polyimides containing siloxane groups in the main chainPOLYMER INTERNATIONAL, Issue 9 2009Mariana-Dana Damaceanu Abstract BACKGROUND: Among the polymers widely studied for applications in advanced techniques, aromatic polyimides have received considerable attention due to their outstanding thermal stability associated with good electrical and mechanical properties. However, these polymers are usually difficult to process, being insoluble and without a glass transition. To improve the processing characteristics of polyimides, modification of their structure is often achieved by the introduction of flexible linkages in the macromolecular chain or various substituents on the aromatic rings. RESULTS: A series of polyimides and intermediate polyamidic acids were synthesized from aromatic oxadiazole-diamines and a dianhydride containing a siloxane bridge (R2SiOSiR2). These polymers exhibit good solubility in certain organic solvents and can be cast into thin and very thin films from their solutions. They exhibit high thermal stability with decomposition being above 440 °C and relatively low glass transition temperatures in the range 160,190 °C. These polymers show strong photoluminescence in the blue spectral region. CONCLUSION: The introduction of oxadiazole rings together with siloxane groups into the chains of aromatic polyimides gives highly thermostable polymers with remarkable solubility and film-forming ability and that emit blue light, being attractive for applications in micro- and nanoelectronics and other related advanced fields. Copyright © 2009 Society of Chemical Industry [source] Optimization of Electrochemical and Peroxide-Driven Oxidation of Styrene with Ultrathin Polyion Films Containing Cytochrome P450cam and MyoglobinCHEMBIOCHEM, Issue 1 2003Bernard Munge Abstract The catalytic and electrochemical properties of myoglobin and cytochrome P450camin films constructed with alternate polyion layers were optimized with respect to film thickness, polyion type, and pH. Electrochemical and hydrogen peroxide driven epoxidation of styrene catalyzed by the proteins was used as the test reaction. Ionic synthetic organic polymers such as poly(styrene sulfonate), as opposed to SiO2nanoparticles or DNA, supported the best catalytic and electrochemical performance. Charge transport involving the iron heme proteins was achieved over 40,320 nm depending on the polyion material and is likely to involve electron hopping facilitated by extensive interlayer mixing. However, very thin films (ca. 12,25 nm) gave the largest turnover rates for the catalytic epoxidation of styrene, and thicker films were subject to reactant transport limitations. Classical bell-shaped activity/pH profiles and turnover rates similar to those obtained in solution suggest that films grown layer-by-layer are applicable to turnover rate studies of enzymes for organic oxidations. Major advantages include enhanced enzyme stability and the tiny amount of protein required. [source] | ||||||||||