bluuebunny/crossref_metadata_2025 huggingface dataset:
Basic research in a Japanese electronics corporation
Authors: Asai Shojiro
Published: December 2004

The Advanced Research Laboratory of Hitachi Ltd. was set up in 1985 to conduct basic research—as part of the corporate research and development program—in purpose‐built facilities away from the rest of the company. The philosophy bhind the decision to create such a laboratory with its own budget and administrative system is outlined, and the interests and recent achievements of research groups there are briefly surveyed.
Plasma enhanced chemical vapor deposition of vanadium carbide VC1−x and VOx from vanadocene Cp2V
Authors: Deutschmann Lutz , Messelhäuser Johannes , Suhr Harald , Herrmann Wolfgang A. , Härter Peter
Published: December 2004

Plasma enhanced CVD of vanadium carbides and oxides is reported for the first time. Vanadium carbide and vanadium oxides are of technological interest for hard coatings (VC1–x), storage media (VO2), and smart electrochromic windows (V2O5), and until now have been prepared mainly by physical deposition methods. The advantages of the precursor vanadocene are outlined and the influence of experimental parameters such as the hydrogen flow rate and the substrate temperature on the composition and resistivity of the films described.
Scanning Probe microscopy and magnetic resonance
Authors: Manassen Yishay
Published: December 2004

Adaptations of scanning probe microscopy techniques can be used in conjunction with electron spin resonance for surfaces containing isolated paramagnetic spin centers. Scanning the tip over such a surface in the presence of a magnetic field produces reproducible. spatially localized signals. Possible mechanisms explaining this behavior are discussed. The detection of magnetic resonance by atomic force microscopy is also considered. including problems that have had to be overcome and experimental details.
Large second‐order optical nonlinearities and enhanced thermal stabilities in extended thiophene‐containing compounds
Authors: Gilmour Sandra , Marder Seth R. , Perry Joseph W. , Cheng Lap‐Tak
Published: December 2004

The optimiztion of second order optical nonliearity requires molecules with a specific degree of ground‐state polarization. In this connection, studies of extended thiophne‐containing compunds with acceptors that gain aromaticity on charge separation, such as the molecule shown, are described. As it also exhibits good therma stability, this compound is a promising candidate for electro‐optic poled polymer applications.

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Tuning Schottky Barriers by atomic layer control at metal—semiconductor interfaces
Authors: Flores Fernando , Miranda Rodolfo
Published: December 2004

Metal‐semiconductor contacts are essentially of two kinds : ohmic contacts and Schottky barriers. The physics governing the formation of metalsemiconductor Schottky barriers–which are the basis of most electronic devices–and ways of tuning their height are reviewed, concentrating on the theory. It is shown that tuning can be achieved by modifying the interface geometry, by modifying the surface dangling bonds, or, in the case of heterojunction interfaces, by the addition of an interlayer. Directions for (experimental) future research are suggested.
“Open” analogues of azacycloalkane mesogens: Liquid‐crystalline diethylenetriamides
Authors: Stebani Uwe , Lattermann Günter , Wittenberg Michael , Festag Reinhard , Wendorff Joachim Heinz
Published: December 2004

Liquid crystals containing “open” analogues of the mesomorphic amide 1,4,7‐triazacyclononane, i.e., 3,4‐bis(alkoxy)‐ benzoyl substituted diethylenetriamine, are reported, showing that the closed‐ring structure of the central core is not essential for mesomorphism in these compounds. The Figure shows the pronounced pseudo‐focalconic texture observed under the polarizing microscope for the decy1 derivative.

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Electrochemical formation of a self‐doped conductive polymer in the absence of a supporting electrolyte. The copolymerization of o‐aminobenzenesulfonic acid and aniline
Authors: Barbero Cesar , Kötz Rüdiger
Published: December 2004

Electrochemical polymerization without a supporting electrolyte would most probably yield a material with more reproducible and better difined propertis, and is therefore a technique to be encouraged. The formation of an electroactive, self‐doped polymer (see Figure) by electropolymerization is described and the analysis of the resulting films presented.

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The formation of silicon carbide films from disilane derivatives
Authors: Hengge Edwin , Zechmann Arno , Hofer Ferdinand , Pölt Peter , Lux Benno , Danzinger Michael , Haubner Roland
Published: December 2004

The formation of silicon carbide films presents problems arising from the fact that the precursors employed are usually a mixture of compounds. It is demonstrated that high‐quality silicon carbide films (see Figure) can be produced by chemical vapor deposition using easily available disilane derivatives as the precursor.

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Oriented growth of quinquethiophene on SiO2—An atomic force microscopy study
Authors: Böhme Oliver , Ziegler Christiane , Göpel Wolfgang
Published: December 2004

Highly ordered organic films must be prepared and characterized if the electrical properties of future organic‐based electronic devices are to be improved, because it is only then that our understanding of intermolecular transport in polymer films can increase. An atomic force microscopy study is presented that shows that quinquethiophene can be physisorbed on Si02 to form highly ordered layers. A change from layer‐by‐layer to multilayer growth is reported to occur upon completion of the second monolayer.
Electron microscopy studies of amphiphilic self‐assemblies on vitreous ice
Authors: Majewski Jaroslaw , Margulis Lev , Weissbuch Isabelle , Popovitz‐Biro Ronit , Arad Talmon , Talmon Yeshayahu , Lahav Meir , Leiserowitz Leslie
Published: December 2004

The structure of self‐assemblies of amphiphiles formed at the air–aqueous solution interface can be determined by cryo transmission electron microscopy (Cryo‐TEM). The method is based on fast vitrification of the thin layer of aqueous solution covered with amphiphilic monolayer by plunging the specimen into liquid ethane at its freezing point. During the process of fast cooling the aggregates maintain their two‐dimensional crystalline integrity and structure, as demonstrated by comparative studies involving grazing incidence X‐ray diffraction (GID) at the air‐solution interface, and the Cryo‐TEM measurements of the same amphiphilic systems on vitreous ice. Bright‐field and dark‐field images from the Cryo‐TEM observations provide more detailed information than from epifluorescence and Brewster angle microscopy. Furthermore, the electron diffraction patterns have the additional advantage that they allow structural characterization of the crystallites almost at a molecular level, and furnish data on micro twinning and defects occurring between crystalline domains. Cryo‐TEM has been applied to elucidate the structure of 2‐D and 3‐D self‐aggregates of amphiphilic alcohols, acids and their cadmium salts, bola‐amphiphiles and mixed monolayers. Epitaxial crystallization of hexagonal ice underneath the monolayer of long chain alcohol was also directly demonstrated by this method.
Conductivity in redox modified conducting polymers. In‐situ conductivity of poly(cyclopentadithiophenes) bearing p‐nitrophenyl and 4‐N‐methylpyridinium groups
Authors: Zotti Gianni , Berlin Anna , Pagani Giorgio , Schiavon Gilberto , Zecchin Sandro
Published: December 2004

Redox‐modified polythiophenes exhibiting the highest mixed‐valence conductivities of any polymer containing a pendant redox group are reported. The ordering of the polymer, in which the backbone has been oxidized to a bipolaron conducting state and the redox sites have been reduced to a mixed‐valence conducting state, encourages inter‐site hopping and results in the high conductivities. Electron interactions are shown not have an influence on the conduction.
Ultrathin membranes of molecularly reinforced liquids on porous substrates
Authors: Seufert Michael , Fakirov Christo , Wegner Gerhard
Published: December 2004

Hairy‐rod‐like macro‐molecules are reported to useful materials in the fabrication of membranes. Cellulose alkylethers, cross‐linked through cinnamyl side groups (see Figure), are transferred onto a Celgard 2400 substrate using the Langmuir–Blodgett technique. The preparation and the characteristics of the membranes are presented.

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Superconductor thin films: Topotactic corrosion mechanism of YBa2Cu3O7 with Water Vapor
Authors: Börner Ralph , Paulus Werner , Schöllhorn Robert , Kabius Bernd , Schubert Jürgen
Published: December 2004

Corrosion in high‐Tc supercnductors (HTSC) caused by water vapor is examined. Htsc thin films prepared usig the laser ablation technique are shown to lose their superconducting properties due to the topotactic formation of a new hydroxylated phase which is a result of the corrosion. The mechanism of the corrosion process, which could be important in future applications of HTSC, is discussed.
Reorganizing a major materials research institute in fast Germany—IFW dresden
Authors: Warlimont Hans
Published: December 2004

Scientific institutes in East Germany underwent huge changes in their organization, funding, and research priorities as a result of the reunification of Germany. The Director of one of the most important institutes. “The Institute of Solid State and Materials Research” in Dresden (IFW), traces the development of the political and scientific environment for materials research in the former East Germany and describes the challenges still to be met, in terms of personnel development, the quest for competitiveness, and the organization of funding
Lyotropic polymorphism in oxovanadium complexes
Authors: Zhu S. Sherry , Swager Timothy M.
Published: December 2004

Ionic transition metal compounds which exhibit mesomorphism in aqueous systems are reported. These oxovanadium‐based surfactants display binary (surfactant/H2O) and ternary (surfactant/H2O/decanol) mesomorphism and represent a step towards the development of lyotropic materials with large magnetic anisotropies.

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Charge transport and molecular dynamics in columnar stacks of liquid crystalline phthalocyanine derivatives
Authors: Groothues Herbert , Kremer Friedrich , Schouten Pieter G. , Warman John M.
Published: December 2004

Broadband dielectric spectroscopy has been employed to study the electric charge transport and molecular dynamics in columnar stacks of liquid crystalline phthalocyanine derivatives, materials which are of interest as one‐dimensional semiconductors or as photoconductors. Three relaxation processes and a conductivity contribution have been identified and it is concluded that the solid‐to‐liquid crystalline phase transition has no influence on the temperature dependence of the conductivity.
Transition metal oxide films
Authors: Uekawa Naofumi , Kaneko Katsumi
Published: December 2004

The sol‐gel method can be used to produce multicomponent oxide materials which have a homogeneous composition even at the atomic level. Thin transition metal oxide films are shown to exhibit different properties from those of the bulk materials and both the crystal structure and the valence state of the materials can be sensitively controlled by doping. Recent progress in the field is reviewed, including the production of highly oriented films, valence‐controlled oxides, the control of instable phase formation and atmosphere‐sensitive structural transformations.
Microengineered conducting composites from nanochannel templates
Authors: Huber Carmen , Sadoqi Mostafa , Huber Tito , Chacko Daborah
Published: December 2004

Novel nanostructures of conducting materials (e.g. see Figure) generated by the template approach are becoming available through a variety os syntheses, processes, and hosts. Here, a class of electronic composites prepared by the injection of the conducting melt into nanochannel templates is described. The injection process, and the analysis and potential uses of the composite microstructures are discussed.

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Optical information processing using alkali‐metal vapors
Authors: Ai Bing , Knize Randall J.
Published: December 2004

Nonlinear optical materials include inorganic single crystals, doped glasses, liquid crystals compound semiconductors and organic dyes. Here, an unusual type of NLP materials, with a very simple structure, alkalimetal vapors, are discussed. The vapors have been found to be among the best nonlinear optical materials for information processing in terms of several figures of merit. The “materials” and their applications are reviewed.
C60 derivatives embedded in sol‐gel silica films
Authors: Maggini Michele , Scorrano Gianfranco , Prato Maurizio , Brusatin Giovana , Innocenzi Plinio , Guglielmi Massimo , Renier Alessandro , Signorini Raffaella , Meneghetti Moreno , Bozio Renato
Published: December 2004

Trasparent sol‐gel thin films and monoliths containing fullerene derivatives (e.g. see Figure) are reported. The sol‐gel technique provides a low‐temperature method to poduce homogeneous thin films and preliminary measurements reveal that these new commposite materials, the first sol‐gel materials to contain C60 or its derivatives, exhibit interesting optical limiting properties.

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Advanced materials and chemical vapor deposition
Authors: Gregory Peter
Published: December 2004

Chemical vapor deposition (CVD) is an important technique used to produce thin films of a wide variety of materials. It finds applications, for example, in the semiconductor industry in the production of chips, and is used to deposit6 ceramics, metals, semiconductors, and even organics. Towards the back of this issue a new section devoted exclusively to CVD and related technologies appears. every two months a similar section will be included in AM. The Essay describes the new section and our plans for its development.
The Colloid Chemical Approach to Nanostructured Materials**
Authors: Fendler Janos H. , Meldrum Fiona C.
Published: December 2004

Nanocrystalline particulate films, dispersions of nanoparticles in monolayers in which the inter‐particle distances can be controlled, and systems containing nanoparticles incorporated between the head groups of organic thin films (see Fig.) produced using a wet colloid‐chemical approach are reviewed. Size‐quantized metallic, magnetic, and semiconducting particles are cosnidered and the development of nanostructured devices discussed

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Ferroelectric and electroclinic properties of the chiral mesogen {Bis‐[N‐4‐(S‐(–)‐β‐citronelloxy)Phenyl‐4′‐(N‐Dodecyloxy)‐salicylaldiminato]}Palladium(II)**
Authors: Ghedini Mauro , Pucci Daniela , Scaramuzza Nicola , Komitov Lachezar , Lagerwall Sven T.
Published: December 2004

Chiral metallomesogens, especially those exhibiting SA* and SC* phases, are of potential interest for applications in electro‐optics. The performance of the materials depends on a number of factors, including spontaneous polarization, switching speed, and tilt angle. Here, the first reports of the electroclinic behavior of a number of metallomesogens are made.
Organic molecular beam deposition of metallophthalocyanines for opto‐electronics applications
Authors: Yamashita Akira , Hayashi Takayoshi
Published: December 2004

Organic molecular beam deposition (OMBD) enables the deposition of various materials under optimum conditions. This review is restricted to films of metallophthalocyanines (see Figure) and related compounds, which are of interest for opto‐electronic applications. Following a description of typical apparatus and conditions, epitaxially grown pseudomorphic films, films with bulk structure, and multilayers are reviewed.

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Extended bis‐fused tetrathiafulvalenes incorporating a heteroaromatic π‐electron spacer
Authors: Misaki Yohji , Sasaki Toshihiro , Ohta Takehiro , Fujiwara Hideki , Yamabe Tokio
Published: December 2004

New π‐electron donors are being sought for the preparation of organic conductors. The first synthesis of bis‐fused π‐electron donors incorporating a heteroaromatic π‐electron spacer (see Figure) is reported. The electrochemical properties of 3a–c and 4a–c and the crystal structure of 3c are presented, the results for the TCNQ complexes 3a and 4a confirming that the fusion of two donor units is a suitable strategy for the development of highly conducting molecular complexes.

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AFM studies of the initial stages of spin‐coated prepolymer film growth on silicon wafers
Authors: Gesang Thomas , Höper Ralf , Possart Wulf , Petermann Jürgen , Hennemann Otto‐Diedrich
Published: December 2004

Polymeric film growth on inorganic substrates plays an important role in the technology of sensors and microelectronics. A study of the film growth of a prepolymer of the dicyanate of bisphenol A (DCBA) spin‐coated onto silicon substrates is presented in which layer‐by‐layer growth is demonstrated. This mode of growth is thought to be related to an enrichment of the trimer (see Figure) including a triazine ring.

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Selective construction of electrical connections using an organic charge‐transfer salt
Authors: Gurtner Christian , Sailor Michael J.
Published: December 2004

The growth and “pruning” of electrical connections between two platinum wires by electrocrystallization of the charge‐transfer salt TTFBrx is reported. Crystals not involved in the connection can be removed by electrochemical reduction (see Figure). This method is a step towards the fabrication of complex structures without the use of a photolithographic or morphologic template.

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Ferroelectric liquid crystalline block copolymers
Authors: Omenat Ana , Hikmet Rifat A. M. , Lub Johan , van der Sluis Paul
Published: December 2004

Ferroelectric liquid crystal (LC) polymers have several advantages compared to low molecular weight ferroelectric LCs (as well as a few disadvantages). The synthesis, characterization, and physical properties of a ferroelectric LC homopolymer and a related new ferroelectric LC polymer system—consisting of a block copolymer with microdomain morphology—are reported. The nearly total absence of hysteresis indicates that the system is monostable, which could make such polymers suitable for display applications with active matrix addressing.
Pulsed field gradient NMR studies of small molecule diffusion in amorphous microporous silicas
Authors: Krause Cordula , Klein Stephan , Kärger Jörg , Maier Wilhelm F.
Published: December 2004

The channel system is a new class of porous materials can be studied by a combination of catalytic results, simple physicochemical characterization, and physical investigations. The investigations described here include the physisorption of small probe molecules, pulsed field gradient (PFG) NMR of selected small molecules, and the effect of surface polarity on diffusivity. These techniques will be useful in the search for novel microporous materials—for which there is a growing need—as an alternative to zeolites.
Donor/acceptor‐substituted phenylenevinylenes
Authors: Klärner Gerrit , Former Carsten , Yan Xiaoling , Richert Ranko , Müllen Klaus
Published: December 2004

The incorporation of donor/acceptor moieties into poly(p‐phenylenevinylene) has been accomplished by a simple cation–anion coupling reaction. The reaction was used to create a series of oligomers, which were then investigated by dielectric spectroscopy in order to study strong dipole moments along the conjugated chain. The information obtained by this method should elucidate cooperative dipole–dipole interactions and help to improve the poling stability of polymers in nonlinear optical devices.
The proposals to split‐up Japan's NTT
Authors: Fujimoto Masatomo
Published: December 2004

The fate of researchers at NTT, Japan's telecommunications company, has been hanging in the balance since 1982, when the debate first began about whether to split‐up NTT. The next decision is due in March 1997. Professor Fujimoto briefly traces the history of the debate and considers the possible consequences of a split: Would it encourage or discourage competitiveness? What would be the effect on long‐term, fundamental research compared to short‐term, product‐oriented projects? The present organizational structure of NTT's R & D is outlined.
Novel vitrifiable liquid crystals as optical materials
Authors: Chen Shaw H. , Shi Hongqin , Conger Brooke M. , Mastrangelo John C. , Tsutsui Tersuo
Published: December 2004

Vitrifiable liquid crystals (VLCs) have several advantages in optical applications: long‐term mesomorphic stability, environmental durability, ease of processing into thin films, and the capability of large aperture. A generic approach is demonstrated for the molecular design of VLCs with an elevated glass‐transition temperature, in which a subtle balance must be struck between order (LC mesomorphism) and disorder (glass). Selected samples are used to illustrate potential applications in the control of light polarization and polarized photoluminescence.
Optical and structural properties of new discotic acrylates polymerized in the discotic nematic phase
Authors: Favre‐Nicolin Christine D. , Lub Johan , van der Sluis Paul
Published: December 2004

Discotic liquid crystals can be used as optical compensation layers to improve the viewing angle of twisted nematic liquid crystal displays, for example. The in situ photopolymerization of newly synthesized acrylates is shown to result in oriented films with a negative birefringence. The transition temperatures, birefringence, and thermal stability were measured and the structure of the polymers was determined by wide‐angle X‐ray diffraction in order to explain the difference in optical properteis between various polymers.
Red–green–blue light emission from a thin film electroluminescence device based on parahexaphenyl
Authors: Leising GÜNther , Tasch Stefan , Brandstatter Christoph , Meghdadi Farideh , Froyer Gerard , Athouel Laurence
Published: December 2004

For colored flat panel displays electroluminescent organic semiconductors are very promising. A novel means is described for the realization of red, green, and blue (RGB) dots based on all all‐organic color transformation technique. The construction of the parahexylphenyl‐based electroluminescence device and its combination with suitable matrix dye layers and dielectric mirrors and filters are outlined. The simplicity of the production of the device and the tunability of the comitted colors make this technique technologically attractive.
Benzodithiophene Rings as Semiconductor Building Blocks
Authors: Laquindanum Joyce G. , Katz Howard E. , Lovinger Andrew J. , Dodabalapur Ananth
Published: December 2004

An organic p‐type semiconductor based on benzodithiophene building blocks is reported for the first time. The synthesis and electrical and morphological characterization of a dimer compound (see Figure) are described, including field‐effect measurements on thin film transistors, X‐ray diffraction, molecular modeling, and electron microscopy. The exceptional thermal stability is noted.

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Highly ordered vacuum‐deposited thin films of metallophthalocyanines and their applications in field‐effect transistors
Authors: Bao Zhenan , Lovinger Andrew J. , Dodabalapur Ananth
Published: December 2004

Metallophthalocyanine thin films, obtained by vacuum deposition as highly ordered, uniquely oriented films (the Figure shows an iron phthalocyanine film deposited at 200°C), have been sued to fabricated organic field‐effect transistors (FETs). It is demonstrated that the substrate temperature during deposition greatly affects the substrate temperature during deposition greatly affects the electric properties of the devices. FIG.

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Demonstration of a nanolithographic technique using a self‐assembled monolayer resist for neutral atomic cesium
Authors: Prentiss Mara , Berggren Karl K. , Younkin Rebecca , Cheung Eunice , Tinkham Michael , Ralph Daniel C. , Black Charles T. , Whitesides George M. , Black Andrew J.
Published: December 2004

A new lithographic method of making nanostructures is demonstrated in which a patterned beam of neutral cesium atoms is used to damage a ∼1.2‐nm‐thick self‐assembled monolayer resist of alkanethiolates on gold. The attractive features of cesium for atomic lithography and the current techniques for neutral atom lithography are sketched. The method is detailed and investigations of the damage to the surface are described. This can be viewed as a first step towards fabricating nanostructures in silicon using optically patterned neutral atomic beams.
Extremely large mesoporous carbon fibers synthesized by the addition of rare earth metal complexes and their unique adsorption behaviors
Authors: Yasuda Hajime , Tamai Hisashi , Ikeuchi Makiko , Kojima Shigeyuki
Published: December 2004

Extremely highly mesoporous activated carbon fibers (see Figure) have been synthesized for the first time from pitch fibers containing rare earth metal complexes. These fibers have potential applications in the purification of drinking water, for example, owing to their ability to absorb giant molecules such as humic acid. Investigations of the absorption behavior of the fibers are reported. fig.

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Formation of monodispersed ultrafine platinum particles and their electrophoretic deposition on electrodes
Authors: Teranishi Toshiharu , Miyake Mikio , Hosoe Masahiro
Published: December 2004

Ordered ultrafine platinum particles are expected to have properties differing from those of isolated particles, however, few measurements have been made because of the difficulty of producing monodispersed Pt particles. A method is reported for controlling the size and size distribution of polymer‐protected ultrafine Pt particles, which can be ordered densely in two dimensions to give Pt particle monolayers by electrophoretic deposition. The structure of the particles and the importance of the nucleation rate in determining the size and distribution are discussed.
Thermal and optical characterization of high purity α‐octithiophenk
Authors: Fichou Denis , te Ulade‐Fichou Marie‐Paule , Horowitz Gilles , Demanze Frédéric
Published: December 2004

The preparation of high purity α‐octithiophene (α‐8T) by vacuum sublimation and the investigation of its optical properties in solution and as thin films and single crystals are reported. α‐8T is probably the ultimate unsubstituted oligothiophene to be processable as a pure crystalline compound. In addition, the first experimental evidence for unsubstituted α‐12T (see Figure) is presented.

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Synthesis and characterization of highly efficient and thermally stable diphenylamino‐substituted thiophene stilbene chromophores for nonlinear optical applications
Authors: Jen Alex K.‐Y , Cai Yongming , Bedworth Peter V. , Marder Seth R.
Published: December 2004

Highly nonlinear chromophores with good thermal stabilities (> 250 °C) are required if organic polymeric materials are to be developed for electro‐optical (EO) applications. The synthesis and characterization of highly efficient and thermally stable diphenylamino‐substituted thiophene stilbenes (e.g., see Figure) are reported, one of which was used to form a high‐EO‐coefficient composite with a polyquinoline.

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Inherent interference‐filter polymer light‐emitting diodes
Authors: Barta Piotr , Birgerson Jonas , Guo Shuwen , Arwin Hans , Salaneck William R. , Zagórska Malgorzata
Published: December 2004

A global or “systems” approach to the design of polymer‐based light‐emitting devices is shown to be important for an understanding of the details of light emission from these devices. A self‐interference‐filter type of light‐emitting device with a very narrow spectral output–a prerequires for many applications but difficult to realize because of the typically broad electroluminescence emission spectrum–is described, in which color selection is achieved by the appropriate combination of layer thickness and values of refractive index of the components of the device structure.
Ultrafine AIN and Al‐AlN powders: Preparation by DC Arc plasma and thermal treatment
Authors: Li Hongdong , Yang Haibin , Zou Guangtian , Yu San
Published: December 2004

Pure, white, nanosized aluminum nitride powder in a wurtzite structure has been prepared using the DC are plasma method. Aluminum nitride is an important ccceramic material which exhibits high thermal conductivity, high hardness, good corrosion resistance, and low thermal expansivity. The most critical factors in the production of advanced ceramics are the purity and homogeneity of the starting powders. The new method allows the production of ultrafine, pure A1N and Al‐A1N composite materials.
Chemical tuning of the electronic properties of differently substituted 1,4‐bis(styryl)benzenes, 2,6‐bis(styryl)naphthalenes, and bis(thienylvinylene)benzenes and ‐naphthalenes
Authors: Döttinger Stefanie E. , Hanack Michael , Segura José L. , Steinhuber Elke , Hohloch Michael , Tompert Alfred , Oelkrug Dieter
Published: December 2004

Tuning of the electrical and optical properties of a series of polyphenylenevinylene (PPV) derivatives has been demonstrated using photoluminescence spectroscopy. The synthesis of the title compounds is described and the effect of substituting electron‐donating and electron‐withdrawing groups in them is correlated with the photoluminescence spectra and electrochemical data. The compounds are shown to be suitable models leading to an understanding of the behavior of configurated polymers as active layers in light‐emitting diodes.
Nitrido‐sodalite Zn6[P12N24] as a material for reversible hydrogen encapsulation
Authors: Weitkamp Jens , Ernst Stefan , Cubero Fernando , Wester Frank , Schnick Wolfgang
Published: December 2004

Host–guest behavior in a nitrido‐sodalite is reported for the first time. The novel nitrido‐sodalite Zn6[P12N24] has the usual nitrido‐sodalite structure with PN4 corner‐sharing units, as shown i the Figure, except that the central anion and one quarter of the Zn2⊕ ions are absent, producing only partial filling of the β‐cages. Hydrogen encapsulation in the β‐cages is discussed.

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Self‐compression and diamond formation in carbon onions
Authors: Banhart Florian , Ajayan Pulickel M.
Published: December 2004

Carbon onions—concentric spherical graphite layers stacked one inside the other—are stable only during electron irradiation. If the irradiation is continued at high temperature, self‐compression is shown to occur, in which the individual layers are compressed until the onion cores finally transform into diamond crystals, which then grow under further radiation. Two scenarios are sketched for the mechanism of pressureless transformation of graphitic materials into diamond and the consequences of these observations for future work are highlighted.
Tetraethynylethene molecular scaffolding: Nonlinear optical, redox, and amphiphilic properties of donor functionalized polytriacetylene and expanded radialenes
Authors: Schreiber Martin , Tykwinski Rik R. , Diederich François , Spreiter Rolf , Gubler Ueli , Bosshard Christian , Poberaj Igor , Günter Peter , Boudon Corinne , Gisselbrecht Jean‐Paul , Gross Maurice , Jonas Ulrich , Ringsdorf Helmut
Published: December 2004

Polymers with polytriacetylene (PTA) backbone (see the Figure), and also expanded radialenes (a new class of macrocycles with large conjugated all‐carbon cores), are of interest because of their intrinsic two‐dimensional π‐electron conjugated pathways. The synthesis, electrochemical characteristics, and linear and nonlinear optical properties of donor‐functionalized polytriacetylene and donor end‐capped expanded radialenes are reported and discussed.

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Molecular patterning using two‐dimensional polymer langmuir–blodgett films
Authors: Aoki Atsushi , Miyashita Tokuji
Published: December 2004

Langmuir–Blodgett (LB) films for high‐resolution resists for the preparation of integrated circuits with higher densities are reviewed briefly. A technique based on the polymerization of monomeric LB films and a newer one based on the two‐dimensional cross‐linking of a polymeric LB film are described. It is demonstrated that cross‐linkable polymeric LB films have the ability to create high‐resolution molecular patterning with nanometer (layer) thickness. Examples of patterns produced with such films are presented.
Room temperature silicon wafer bonding with ultra‐thin polymer films
Authors: Kräuter Gertrud , Schumacher Andreas , Gösele Ulrich , Jaworek Thomas , Wegner Gerhard
Published: December 2004

Bonding of silicon wafers is required in microelectronics fabrication, for example. A room‐temperature bonding process that leads to sufficient bond strength is necessary for bonding semi‐processed wafers, i.e., those already containing temperature‐sensitive structures. The room‐temperature bonding of hydrophobic wafers is reported for the first time, an ultra‐tin Langmuir‐Blodgett film of a “hairy” rod‐like polymer being used as an intermediate layer. The effect of the polymer layer on the surface roughness is investigated and possible directions o future work are indicated.
White‐light electroluminescence from self‐assembled Q‐CdSe/PPV multilayer structures
Authors: Gao Mingyuan , Richter Bernd , Kirstein Stefan
Published: December 2004

Inorganic nanoparticles in organic/inorganic hybrid devices are expected to have properties of interest for electroluminescence applications. The preparation of films of CdSe nanoparticles and poly(phenylenevinylene), PPV, by means of self‐assembly is presented and photoluminescence and electroluminescence studies of these films are described. It is shown that nearly white‐light emission is achieved from a twenty‐layer film and that the emission orgininates most probably from the nanoparticles alone. The role of the PPV is discussed.
Multinuclear solid‐state‐NMR studies of hybrid organic‐inorganic materials
Authors: Templin Markus , Wiesner Ulrich , Spiesss Hans W.
Published: December 2004

The powder of multinuclear solid‐state NMR for the investigation of the structural aspects of hybrid organic‐inorganic materials is demonstrated by the results presented here. It is shown that information about the organic groups can be obtained from 1H and 13C NMR and about the inorganic groups from 27Al and 29Si NMR; changes caused by the additional of a hardening component are revealed. Organic‐inorganic materials are of interest because they combine properties typical of inorganic compounds with the favorable mechanical properties of synthetic polymers.
βco‐(ET)2I3: Non‐electrochemical synthesis and structural and physical properties of an organic superconductor with 7.1 K ≤ Tc ≤ 7.9 K
Authors: Müller Harald , Svensson S. Olof , Fitch Andrew N. , Lorenzen Maren , Xenikos Dimitrios G.
Published: December 2004

Synthesis of the superconducting radical cation salt βco‐(ET)2I3 obtained by the direct oxidation of either hydrogenated or deuterated bis(ethylenedithio)tetrathiafulvalene (ET) with a stoichiometric amount of iodine is reported. The structure and physical properties of the resulting compounds are presented and compared with those of other (ET)2I3 phase. βco‐(ET)2I3 is found to have very similar superconducting properties to those of αt‐(ET)2I3 and the question is raised as to whether they are actually distinct phases.
Fullerenes in membranes: Structural and dynamic effects of lipophilic C60 derivatives in phospholipid bilayers
Authors: Hetzer Michael , Bayerl Sybille , Camps Xavier , Vostrowsky Otto , Hirsch Andreas , Bayerl Thomas M.
Published: December 2004

Intercalation of lipo‐fullerenes between two monolayers of a lipid bilayer can result in the formation of rodlike structures that exhibit reversible longrange ordering (see Figure). This and other interesting properties of fullerne/membrane composite systems are reported. An arrangement of C60 in the bilayer capable of explaining of experimental observations is also suggested.

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A conjugated polymer‐based voltage‐regulator device
Authors: Arias Ana C. , Hümmelgen Ivo A. , Meneguzzi Alvaro , Ferreira Carlos A.
Published: December 2004

A voltage‐regulator multilayer device based on teh conjugated polymer PAN (poly(5‐amino‐I‐naphthol)) sandwiched between silver and tin oxide electrodes is reported. It is shwon that after breakdown at Vcrit the devices is self‐regulatory, maintaining an approximately constant potential difference Vstab between the tin oxide and silver electrodes; Vcrit and Vstab depend on the polymer film thickness. The current–voltage characteristic is compared with that of another voltage regulator, the Zener diode.
Weathering investigation of PVC coatings on iron sheets by the NMR MOUSE
Authors: Zimmer Gisela , Guthausen Andreas , Schmitz Udo , Saito Koji , Blümich Bernhard
Published: December 2004

A new kind of MOUSE–the NMR mobile universal surface explorer–makes NMR investigations possible on composites with ferromagnetic components, which were previously excluded from such studies, because inhomogeneous magnetic fields are used in the first place. An example application is described, to relaxation measurements of polyvinylchloride (PVC) coatings on iron sheets. It is demonstrated that new and artificially weathered PVC coatings can be distinguished by means of their different transverse relaxation times.
Photo‐oxidation of poly(p‐phenylenevinylene)
Authors: Xing Kezhao Z. , Johansson Nicklas , Beamson Graham , Clark David T. , Brédas Jean‐Luc , Salaneck William R.
Published: December 2004

The operating lifetime of light‐emitting devices (LEDs) based on poly(p‐phenylenevinylene) (PPV), one of the most widely used conjugated polymers for polymer‐based LEDs, is sensitive to air exposure. The effects associated with the photo‐oxidation of PPV in air are examined. Possible photo‐induced oxidation products are proposed based on simulations using stilbene as a model compound. X‐ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and quantum‐chemical calculations all indicate that a series of photo‐oxidation products from on the surface of the PPV thin films.
Molecular surface orientation field of a langmuir monolayer determined by second‐harmonic microscopy
Authors: Flörsheimer Mathias , Salmen Heiner , Bösch Martin , Brillert Christof , Wierschem Maria , Fuchs Harald
Published: December 2004

The characterization of a Langmuir monolayer at a water surface by means of second‐harmonic microscopy (SHM) is reported. Details of the technique and the theory are presented in the following article. The application described here illustrates the main advantages of SHM: it provides quantitative information on the microscopic level and reveals additional information compared to linear microscopy techniques. It is demonstrated to open up new perspectives for the development and improvement of polar organic materials, starting from polar monolayers at an interface.
Second‐harmonic microscopy — a quantitative probe for molecular surface order
Authors: Flörsheimer Mathias , Bösch Martin , Brillert Christof , Wierschem Maria , Fuchs Harald
Published: December 2004

Second‐harmonic microscopy—an application of which is presented in the previous article—is a fast quantitative technique for the imaging of interfaces such as that in the Figure. The theory of the technique, which is based on the generation of second‐harmonic light specifically at surfaces or interfaces due to their lack of centrosymmetry, is outlined and the interpretation of the results discussed.

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Multiproperty molecular materials combining conductivity and second‐order optical nonlinearities
Authors: Lacroix Pascal G. , Nakatani Keitaro
Published: December 2004

The combination of electrical and nonlinear optical (NLO) properties in one material is described for the tetracyanoquinodimethane (TCNQ) radical ion paired with N‐methylstilbazolium‐based chromophores. One of the resulting hybrid materials has a conductivity of 2.3 × 10−3 Ω−1 cm−1 and a second‐harmonic generation efficiency 45 times that of urea. During the predicted transition from electronics to photonics, optoelectronics, which requires multiproperty materials such as those described here, will play an important role.
Electroluminescence from carbazole dimers
Authors: Romero Danilo B. , Nüesch Frank , Benazzi Tayeb , Adès Didier , Siove Alain , Zuppiroli Libero
Published: December 2004

Blue light‐emission from a single‐layer organic LED (light‐emitting diode) based on carbazole dimers is reported. The device fabrication, involving vacuum sublimation of the dimer onto an indium tin oxide covered glass substrate, is described and the source of the electroluminescence elucidated. It is deduced that confined intra‐dimer luminescence excitations and a balanced double‐charge injection result in a device with good luminance and modest external quantum efficiencies. Of the three primary colors required for full‐color display applications, blue has been the most elusive to obtain.
First evidence of stimulated emission from a monolithic organic single crystal: α‐Octithiophene
Authors: Fichou Denis , Delysse Stephane , Nunzi Jean‐Michel
Published: December 2004

The gap between laser dyes and luminescent polymers—on the way to the polymer laser diode‒is bridged by conjugated oligothiophenes, according to the results reported here. Evidence for optically pumped spectral narrowing in ultrathin single crystals of α‐octithiophene (α‐8T) is presented. For example, the gain narrowing of two narrow emission lines that appear when the crystals are pumped can be described in the usual framework of stimulated emission. In contrast to dye‐doped crystals, α‐8T provides both the emitter and the optical cavity.
Preparation and purification of metal fluorides for crystals and glasses
Authors: Kinsman B. E. , Hanney R.
Published: December 2004

The development of low‐loss fluoride glass fibres for transoceanic telecommunications led to an increased demand for inorganic fluorides with ultrahigh purity in respect of transition metals, rare earths and oxygen. This review paper describes the Merck Ltd strategy for achieving a wide range of metallic fluorides using methods of preparation and purification selected for a combination of technical efficacy and economic practicability. General prepative methods involving aqueous and non‐aqueous routes are described, togehther with purification methods such as ion exchange, zone refining and vacuum sublimation. The special role of ammonium fluoride complexes is discussed. The application of these general methods to the manufacture of fluoride glass components is described, with special reference to the ZBLAN formulation. Additional glass compositions and their individual requirements are also discussed. The parallel application of high‐purity metal fluorides in the growth of optical crystals is emphasised, the history of fluoride ultrapurification having begun with the early demand for high‐quality UV and IR crystals such as CaF2 and LiF.
The single‐molecule approach to the deposition of compound semiconducting materials by MOCVD and related methods
Authors: O'Brient Paul , Haggata Stephen
Published: December 2004

The last 10 years have seen a number of chemists begin to take a serious interest in the deposition of materials such as compound semiconductors. Chemical deposition routes have a number of potential advantages, many of which arise from the fact that growth can take place well away from equilibrium. Chemists are particularly attracted by the idea that a volatile single molecule can deliver the elements of a compound semiconductor to the reaction site. In the present article recent advances in the deposition of compound semiconductors, principally II/VI (12/16) or III/V (13/15) materials, from single‐molecule precursors will be reviewed. The chemistry of these precursors will be discussed in terms of both their synthesis and properties and the effect of the mechanism of their decomposition on the quality of deposited material.
Ion‐selective langmuir blodgett films of a chromoionophore
Authors: Lednev Igor K. , Petty Michael C.
Published: December 2004

Langmuir–Blodgett films built up from an amphiphilic derivative of benzothiazolium styryl dye containing a 1,10‐dithia‐18‐crown‐6 ether group have been found to complex with ‘soft’ polarisable ions such as Ag+ and Hg2+ in water. The films exhibited high sensitivity (stability constant of complex formation K ≈ 105 M−1) and high selectivity (e.g. K(Ag+)/K(Pb2+)> 105) compared with aqueous solutions of similar ionophores. This was attributed to the predominant formation of complexes with ligand–cation stoichiometries of 2:1 in the films.
Titelbild: An Unprecedented Bridging Phenoxyl Radical in Dicopper(II) Complexes: Evidence for an S=3/2 Spin State (Angew. Chem. 3/2005)
Authors: Michel Fabien , Torelli Stéphane , Thomas Fabrice , Duboc Carole , Philouze Christian , Belle Catherine , Hamman Sylvain , Saint‐Aman Eric , Pierre Jean‐Louis
Published: December 2004

Metall‐Radikal‐Wechselwirkungen spielen bei vielen Biokatalysatoren, die Übergangsmetalle enthalten, eine zentrale Rolle. Das Titelbild zeigt die Struktur eines Dikupfer(II)‐Komplexes mit einem Phenoxylradikal als Brückenligand. Die ferromagnetische Kopplung der drei Spins wird durch die schwarzen Pfeile angedeutet. In ihrer Zuschrift auf S. 442 ff. beschreiben F. Thomas et al. Synthese, Struktur und Eigenschaften dieses Komplextyps. Stabilität und Reaktivität werden von der Zahl der Metallzentren und der Art des koordinierenden Solvens bestimmt.
Kinetics of renaturation of denatured DNA. I. Spectrophotometric results
Authors: Subirana Juan A. , Doty Paul
Published: December 2004

The kinetics of renaturation of heat‐ or formamide‐denatured DNA have been studied by following the change of optical density at a constant temperature. Solvents of different ionic strength and various DNA samples have been used. At the lower ionic strengths studied, the reaction follows second‐order kinetics, substantiating the hypothesis that strands of native DNA separate upon denaturation and recombine during renaturation. As the ionic strength is increased at a constant temperature, the reaction deviates from simple second‐order behavior. This appears to be the result of the inhibition to rewinding caused by short helical segments in the denatured DNA which are more stable at the higher ionic strenth.
Kinetics of renaturation of denatured DNA. II. Products of the reaction
Authors: Subirana Juan A.
Published: December 2004

The structure of renatured T4 DNA has been studied by CsCl density‐gradient centrifugation. It has been found that the products of the reaction differ, depending on the method used for denaturation of the DNA. If denaturation is carried out without taking precautions to prevent chain degradation, for example, by heat, the DNA formed by renaturation shows approximately 70% recovery of the native structure as judged by its density. With long times of annealing, the DNA can recover the native density. This behavior is also observed with bacterial DNA samples. On the other hand, if precautions arc taken to prevent chain degradation during denaturation, two products appear as a result of renaturation. One of them is undistinguishable from native T4 DNA, whereas the second one consists of highly aggregated DNA which shows only a partial recovery of the native structure. With long times of annealing, this second species recovers the native density but retains its highly aggregated nature. At higher ionic‐strengths, renaturation follows a different pattern and a single product is formed. The relevance of all these observations to the kinetic anomalies reported in the previous communication is discussed.