ISSN:0005-9021    

DOI:10.1002/bbpc.19910951101

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1991

数据来源: WILEY

摘要:

AbstractThe growth, structure, thermodynamic and electronic properties of ultrathin metal films is discussed, starting from the submonolayer range up to thicknesses at which bulk properties are reached. The following topics are selected from the wide field of phenomena: one‐dimensional crystals, shape and stability of twodimensional crystals, film‐substrate and lateral interactions, electronic structure and bonding, structural transitions and quantum size effects. The substrates used are mainly W(110), Mo(110) and Si(111) surfaces, the film materials several fcc met

ISSN:0005-9021    

DOI:10.1002/bbpc.19910951102

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper addresses growth mechanisms, characterization and properties of thin films grown from the vapor phase. The emphasis is placed on artificial structures such as metastable alloys and layered materials, including superlattices. For metastable alloy formation it is demonstrated that a bombardment of the growing film surface by low‐energy ions can be used to promote growth of metastable alloys even at temperatures high enough for epitaxial films to form. In the case of layered materials it is shown using a combination of X‐ray diffraction and high resolution transmission electron microscopy, that superlattices with atomically sharp interfaces can be grown not only in the case of materials with covalent bonds (e.g., semiconductors) but also in the case of materials with metallic bonds. Finally, some properties of metallic superlattices are also discus

ISSN:0005-9021    

DOI:10.1002/bbpc.19910951103

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1991

数据来源: WILEY

摘要:

AbstractThe Langmuir‐Blodgett technique provides for the possibility to prepare ultrathin layers of macromolecules on solid, planar substrates. In this context a series of novel polymers was synthesized and tested with the aim to develop the materials science background and the methodology to fabricate devices based on such ultrathin layers. This made it necessary to develop or adapt a number of methods to characterize these ultrathin layers at surfaces with regard to homogeneity, orientation phenomena, optical properties and transport behavior. The design of macromolecules described as “hairy‐rods” proved to be particularly successful and novel types of supramolecular architectures could be realized best described as “molecularly reinforced liquids”. First attempts to build prototype devices based on layered assemblies of these nonconventional polymers ar

ISSN:0005-9021    

DOI:10.1002/bbpc.19910951104

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1991

数据来源: WILEY

摘要:

AbstractFluorescent dyes derived from anilino‐pyridinium are studied with respect to their application as probes of voltage‐transients in neuron membranes. Their photophysical properties are characterized in bulk solvents. The spectral features of their voltage‐sensitivity in membranes are determined. A mechanistic scheme of voltage‐sensitivity is proposed. The dyes are applied for optical recording in neurites of cultivated neurons of the leech. The relative sensitivity is evaluated from the fluorescence transients induced by hyperpolarization on the basis of the cable equation. The pervasion of a neuritic tree by action potentials is o

ISSN:0005-9021    

DOI:10.1002/bbpc.19910951105

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1991

数据来源: WILEY

摘要:

AbstractMultiple angle null ellipsometry has been used to obtain information about the optical anisotropy of multilayer Langmuir‐Blodgett films. The data are evaluated with a simplified uniaxial (or biaxial) model system. The optical constants of films made of 22‐tricosenoic acid have been determined tonx,y= 1.51 andnz= 1.54 with a monolayer thickness of 3.2 nm. The data are compared with results from waveguide mode spectroscopy. Phenylhydrazone films have been measured in the spectral region between 420 nm (λmax) and 700 nm. The resulting data imply a tilt of the chromophore dipole direction greater than 45° with respect to the surface n

ISSN:0005-9021    

DOI:10.1002/bbpc.19910951106

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1991

数据来源: WILEY

摘要:

AbstractFocussed laser light can be used to induce chemical or electrochemical reactions in the μm scale. The attainable high power densities allow to achieve fast reaction rates. At metals and insulators thermal heating dominates. On semiconductors short pulses or low energy densities cause mainly electronic processes under isothermal conditions. These will be emphasized in this paper for thin semiconductor films in electrolyte solutions. The induced reactions measured under potentiostatic or potentiodynamic conditions include electron (ETR) and ion transfer (ITR) as well.—Examples are discussed for n‐type semiconducting passive films on some base metals with thicknesses in the range from nm to μm. The ETR depend mainly on the potential showing the tendency to saturation while the ITR depend on the field strength. Doping by ion implantation reduces ETR and ITR as well. Amorphous films show a smaller tendency to inner reactions like breakdown. Bubble formation can be detected in a microscopic scale. Substrate effects are due to epitaxy on various grains, changes of the structure and crystallinity (suboxide and TiN) and electronic processes at the substrate surface (Al/A

ISSN:0005-9021    

DOI:10.1002/bbpc.19910951107

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1991

数据来源: WILEY

摘要:

AbstractThe preparation of highly monodisperse, quantum‐sized CdS particles is described. In these samples a band splitting into discrete exciton‐like states is observed.—Quantum‐sized CdS and PbS particles prepared in situ on highly porous, polycrystalline TiO2electrodes work as highly efficient sensitizers. Photocurrent yields of more than 70% are reported. In the case of PbS it is shown that an efficient electron transfer is only possible with particles in the size quantization

ISSN:0005-9021    

DOI:10.1002/bbpc.19910951108

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1991

数据来源: WILEY

摘要:

AbstractIt is possible to measure the work‐function of polymer coated materials with a Kelvin‐probe. In a humid atmosphere this work‐function is mainly given by the corrosion‐potential of the metal substrate. The use of a scanning Kelvinprobe then allows to map the corrosion potential of polymer coated material with a local resolution of approx. 20 μm and to follow the delamination of polymer coatings as well in the vicinity of defects as on metal substrates, which are contaminated at the metal/polymer interface. Simultaneously, the diffusion of oxygen can be followed with a high local resolution after a jump of the oxygen activity within the gas phase.—The same techniques are used to analyse intrinsic defects within monomolecular LB‐films. In a dry gas phase the Volta potential map corresponds to the distribution of dipole‐potentials and therefore allows to distinguish between covered and uncovered parts of the substrate, as the ordered LB‐film shows rather large dipole‐potentials. In a humid atmosphere the Volta potential map again is dominated by the corrosion potential of the substrate and therefore the delamination of the LB‐film in the vicinity of defects can be studied as well as the stability of the film on the metal substrate far

ISSN:0005-9021    

DOI:10.1002/bbpc.19910951109

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1991

数据来源: WILEY

摘要:

AbstractPlasma polymer films of vinyltrimethylsilane (VTMS) were deposited by radiofrequency (RF. 13.56 MHz) or Microwave (MW, 2.45 GHz) discharges in two reactors of the same volume and geometry.—The polymer films were characterized by electron spectroscopy for chemical analysis (ESCA) and infrared spectroscopy (FTIR). It turned out, that the RF—and the MW—polymers had almost the same Si/C‐composition ratio of 1/5 in the entire range of RF‐and MW‐power (60–150 W). Although the Si/C film‐composition remains almost constant, the binding states of Si‐and C‐atoms in the respective ESCA‐spectra are changing. While the CSi part of the C1s‐peak increases with the RF‐or MW‐power, the CH/CC part of the peak decreases, indicating a loss of hydrogen in the polymer films.—Obviously the fragmentation of the VTMS‐monomer is quite different for the two types of plasma discharges. While films of the RF‐plasma clearly show strong contributions of the methyl and vinyl groups, these groups are completely missing for the MW‐plasma polymers.—From these results structure models

ISSN:0005-9021    

DOI:10.1002/bbpc.19910951111

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1991

数据来源: WILEY