Advanced Materials

Cover image for Advanced Materials

March, 2000

Volume 12, Issue 5

Pages 327–381

    1. Application of Ring-Opened Poly(ferrocene)s as Protective Charge Dissipation Coatings for Dielectrics (pages 327–330)

      R. Resendes, A. Berenbaum, G. Stojevic, F. Jäkle, A. Bartole, F. Zamanian, G. Dubois, C. Hersom, K. Balmain and I. Manners

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<327::AID-ADMA327>3.0.CO;2-L

      Protective, charge dissipation coatings for dielectrics are of considerable significance for satellite and electronics applications. Poly(ferrocenylsilane) has been used to coat the right half of the Mylar sample shown in the Figure. Upon exposure to a 20 eV electron beam, high-energy arc discharges resulting from negative charge accumulation occur only on the uncoated (left) half.

    2. “Writing–Reading–Erasing” on Tungsten Oxide Films Using the Scanning Electrochemical Microscope (pages 330–333)

      I. Turyan, U. O. Krasovec, B. Orel, T. Saraidorov, R. Reisfeld and D. Mandler

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<330::AID-ADMA330>3.0.CO;2-8

      A read–write–erase system for micropatterning tungsten oxide films is reported here. The Figure shows blue spots of tungsten bronze formed locally on tungsten oxide film by locally generating a reductant close to the film. The process utilizes the scanning electrochemical microscope (SECM) not only to inject charge but also to study its propagation inside the film.

    3. Nano- and Microengineering: 3-D Colloidal Photonic Crystals Prepared from Sub-μm-sized Polystyrene Latex Spheres Pre-Coated with Luminescent Polyelectrolyte/Nanocrystal Shells (pages 333–337)

      A. Rogach, A. Susha, F. Caruso, G. Sukhorukov, A. Kornowski, S. Kershaw, H. Möhwald, A. Eychmüller and H. Weller

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<333::AID-ADMA333>3.0.CO;2-X

      Colloidal photonic crystals doped with luminescent semiconductor nanocrystals are prepared here by a layer-by-layer deposition technique. This method, which involves the consecutive electrostatic adsorption of polyelectrolyte and nanocrystals such as CdTe onto submicrometer-sized polystyrene latex globules (see Figure), is described as being very versatile and can be extended to the fabrication of either optically active or passive shells of different thickness.

    4. Synthesis and Electronic Properties of Reduced Mesoporous Sodium Niobium Oxides (pages 337–341)

      M. Vettraino, M. L. Trudeau and D. M. Antonelli

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<337::AID-ADMA337>3.0.CO;2-H

      A new series of electronically reduced mesoporous materialsbased on niobium oxide is reported. It is shown for the first time that, upon host–guest intercalation, electron transfer from the guest to the walls of the mesoporous host occurs whilst the porous structure of the material is retained (see Figure). The electronic properties of the host material are demonstrated to be tunable by addition of varying amounts of sodium.

    5. Reactively Sputter-Deposited Titanium Oxide Coatings with Parallel Penniform Microstructure (pages 341–343)

      J. Rodríguez, M. Gómez, J. Lu, E. Olsson and C.-G. Granqvist

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<341::AID-ADMA341>3.0.CO;2-0

      Ordered titanium dioxide films with large and controllable microstructure have been prepared by a low temperature sputtering deposition method. The Figure displays the “parallel penniform” structure of the films, which have very large surface area and excellent contact to the underlying substrate, rendering them potentially important for electrochemical and photoelectrochemical applications.

    6. Polarized Electroluminescence from Aligned Chromophores by the Friction Transfer Method (pages 344–347)

      X. L. Chen, Z. Bao, B. J. Sapjeta, A. J. Lovinger and B. Crone

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<344::AID-ADMA344>3.0.CO;2-P

      A new method for aligning light-emitting materials is reported here: The friction transfer technique was used to produce the poly(tetrafluoroethylene) surface shown in the Figure. The surface has a high density of ridges and grooves with height variations on the ten-nanometer scale, and thin films with high optical quality and controllable thickness were readily obtained. Polarized LEDs fabricated on such surfaces show high dichroic ratios.

    7. Novel Design of Carbon-Rich Polymers for 193 nm Microlithography: Adamantane-Containing Cyclopolymers (pages 347–351)

      D. Pasini, E. Low and J. M. J. Fréchet

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<347::AID-ADMA347>3.0.CO;2-D

      For 193 nm lithographic applicationsrobust polymers containing a high carbon/hydrogen ratio are required. In this paper a novel cyclopolymerization approach is presented for producing chemically amplified resists that are transparent at the imaging wavelength. Upon exposure to a 193 nm laser stepper, features 160 nm in size can readily be obtained (see Fig.).

    8. Novel Electroluminescent Devices Based on Perylene-Doped Sol–Gel Layers (pages 351–354)

      M. Schneider, J. Hagen, D. Haarer and K. Müllen

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<351::AID-ADMA351>3.0.CO;2-X

      A novel approach to the preparation of light-emitting diodes is presented here. Hybrid sol–gel layers have been employed as a film-forming rigid matrix doped with highly fluorescent perylene dyes (e.g., see Fig.) as light emitters. Electroluminescence was found to be remarkable even at incorporation levels as low as 6 wt.-% perylene derivative.

    9. Detection of HF Gas with a Porous Silicon Interferometer (pages 355–359)

      S. Létant and M. J. Sailor

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<355::AID-ADMA355>3.0.CO;2-H

      Detection of HF is important since it is highly toxic and used in large quantities in industrial environments, in particular in the semiconductor and petroleum refining industries. Electrochemical methods have generally been used up to now for HF sensing; however, a major problem is selectivity, i.e., it is not possible to differentiate HF and HCl with electrochemical sensors. These authors report a new technique for HF detection that utilizes a porous silicon interferometer. The method is cheap and is highly selective for HF relative to common interferants.

    10. Development of a New Mesoporous Carbon Using an HMS Aluminosilicate Template (pages 359–362)

      J. Lee, S. Yoon, S. M. Oh, C.-H. Shin and T. Hyeon

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<359::AID-ADMA359>3.0.CO;2-1

      Mesoporous carbon materials are desirable electrode materials and are also useful for the separation of bulky organics. In this article, the templated synthesis of a new high surface area mesoporous carbon using hexagonal mesoporous silica (HMS) aluminosilicate is reported. Preliminary results on the electrochemical double-layer capacitance performance of the material are presented that indicate that it is superior to the commercially available carbon MSC-25. In addition, the pore structure of HMS is indirectly elucidated.

    11. Circularly Polarized Electroluminescence from Liquid-Crystalline Chiral Polyfluorenes (pages 362–365)

      M. Oda, H.-G. Nothofer, G. Lieser, U. Scherf, S. C. J. Meskers and D. Neher

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<362::AID-ADMA362>3.0.CO;2-P

      Circularly polarized electroluminescence (CPEL) has potential application in optical data storage and processing. It was recently discovered that CPEL could be generated from chiral-substituted, conjugated polymers. These authors have synthesized a range of polyfluorenes (e.g., see Figure) that form liquid crystals and emit bluish light with a significant (200 times greater than in the first report) circularly polarized component.

    12. Synchrotron X-ray Diffraction Evidence for Native Defects in the Photovoltaic Semiconductor CuInSe2 (pages 366–370)

      L. Kaplan, G. Leitus, V. Lyakhovitskaya, F. Frolow, H. Hallak, Å. Kvick and D. Cahen

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<366::AID-ADMA366>3.0.CO;2-9

      CuInSe2 is a semiconductor used in solar cells that has appreciable Cu ion conductivity. These authors have used 0.25 Å synchrotron X-radiation to analyze its structure. It is shown that the application of a strong electric field leads to a decrease in electron density on the Cu sites, which sheds light on the role of Cu electromigration in transistor formation (see Figure) and in the photovoltaic activity of CuInSe2.

    13. Liquid Crystal Alignment and Switching in Porous Chiral Thin Films (pages 371–373)

      J. C. Sit, D. J. Broer and M. J. Brett

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<371::AID-ADMA371>3.0.CO;2-P

      Control over the long-range orientation of liquid crystals (LCs) has been achieved by embedding LCs into porous thin films with engineered microstructures. Glancing angle deposition was used to fabricate these porous thin films (see Figure), and results are summarized here that show how the films act as alignment or “backbone” structures for the LCs, inducing orientation of non-chiral nematic LCs in chiral nematic-like phases.

    14. Optimization of Flux Pinning in Bulk Melt Textured 1-2-3 Superconductors: Bringing Dislocations under Control (pages 375–381)

      F. Sandiumenge, T. Puig, J. Rabier, J. Plain and X. Obradors

      Article first published online: 23 FEB 2000 | DOI: 10.1002/(SICI)1521-4095(200003)12:5<375::AID-ADMA375>3.0.CO;2-9

      Structural defects are important in type II superconductors since they are responsible for their supercurrent carrying capacity; however, the engineering of defects has been problematic. This report summarizes the difficulties involved and presents recent results dealing with alternative processing routes, such as high oxygen pressure processing, which gives rise to a higher density of partial dislocations (see Figure) and significantly enhanced critical currents.