摘要:

AbstractThe advent of high‐temperature superconducting metal oxides (SMOs) has prompted an increasing number of studies aimed at the development of new routes to their syntheses, in particular in the form of thin films. The preferred method in this regard has been that of chemical vapour deposition (CVD); however, significant difficulties have been associated with the efficacy of commercial precursors for the group 2 metals, in particular those of the bis(β‐diketonates) of barium, whose co‐ordinative unsaturation leads to cluster formation. The development of alternative β‐diketonate precursor systems has focused upon the synthesis of stable Lewis acid‐base complexes by either inter‐ or intramolecular stabilisation. The results of these studies are described herein, along with a review of the research to date on non‐β‐diketonate derivatives of the group 2 metals, including organometallic, halide, amide, carboxylate and alkoxide compounds. On the basis of the results to date, a series of goals for the synthesis of the ideal precu

ISSN:1057-9257    

DOI:10.1002/amo.860020602

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe optical transmittance and absorption of thin films of monoclinic lead phthalocyanine have been studied as a function of exposure to chlorine and air. The effect of chlorine on the refractive index and dielectric constant of freshly prepared films was estimated from reflectivity data in the photon energy range 2.1–2.6 eV. Responsivity and recovery from gaseous exposure were studied with regard to the applicability of lead phthalocyanine to the fabrication of an optical chlorine senso

ISSN:1057-9257    

DOI:10.1002/amo.860020603

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe self‐assembly technique experimented for the deposition of alkanes and alkyl derivatives on layered compounds at the liquid/solid interface has been successfully extended to the adsorption of poly(3‐decyl‐thiophene) on graphite. The molecular films so obtained have been investigated using scanning tunnelling microscopy (STM). Images taken in both the constant‐current and constant‐height modes show highly packed arrays of molecules characterised by an average length and an average spacing that are in good agreement with results obtained by X‐ray diffraction investigations. Constant‐current images allow one to observe domain formations in preferential directions coincident with the main axes of the graphite lattice, while constant‐height imaging, performed on small areas, allows one to resolve atomic structures within the polymer backbone. In particular, periodic, 0.71 nm spaced features have been identified along the side of the polymer backbone; they can be associated with the length of two monomer units and are attributable to imaging of sulphur atoms

ISSN:1057-9257    

DOI:10.1002/amo.860020604

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this paper we describe the growth of silicon nitride from nitrogen and silane for the first time by capacitively coupled remote PECVD. We report on the effect of process parameters on the composition and properties of the deposited films and we show that by adjustment of these parameters it is possible to produce high‐quality material which could be of interest for electronic applications. Of particular note is that the growth rate is about one order of magnitude higher than any previously reported for nitride growth with remote PECVD using molecular nitrogen as the nitrogen source. We also discuss the mechanism of growth and propose that electron excitation of nitrogen and silane occurs in the gas phase, producing SiHxspecies which are adsorbed on the growing surface. The nitrogen is then incorporated into the layer by heterogeneous reactio

ISSN:1057-9257    

DOI:10.1002/amo.860020605

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractCoherent anti‐Stokes Raman scattering (CARS) has been utilised to monitor the decomposition of trimethylgallium (TMGa) on the reactive internal surface of the protonated form of zeolite Y under metal organic chemical vapour deposition (MOCVD) conditions designed to produce GaP deposits that exhibit quantum‐size effects. The CARS data clearly reveal the facile room temperature decomposition of TMGa in the zeolite, as evidenced by the detection of increasing levels of methane with increasing reaction time. In addition, the zeolite samples were analysed by solid state nuclear magnetic resonance with magic angle spinning (MAS NMR) before reaction, after reaction of TMGa and after subsequent reaction with phosphine at 300°C. These data reveal that TMGa reacts with acid sites in the zeolite 12‐rings, resulting in species containing methyl groups. Subsequent exposure to phosphine removes these methyl group protons, leaving various, as yet not fully characterised, phosphorus species. Exposure to phosphine does not appear to regenerate the acid sites on the z

ISSN:1057-9257    

DOI:10.1002/amo.860020606

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe synthesis of a new polar amphiphilic derivative of indandione‐1,3 pyridinium betaine (IPB) with different lengths of the aliphatic tail, containing 11 (C11IPB) and 17 (C17IPB) carbon atoms respectively, is described. The electronic structure (charge distribution, energy spectra, dipole moments in ground and excited states) of the IPB molecule has been calculated in the framework of the MO CNDO methods. Studies of compression π‐Aisotherms of these compounds show that C17IPB forms two stable phases of monolayer on the water surface, one in the 10–30 mN m−1and the other in the 35–50 nM m−1surface pressure region. The corresponding areasA0per molecule are 37 and 33 Å2respectively. Techniques for the preparation of Langmuir‐Blodgett (LB) multilayers of C17IPB in the high‐pressure region (π = 40 mN m−1) on glass, quartz or sapphire substrates are described. C17IPB forms LB multilayer films of Z‐type configuration with oriented dipole moments. Ellipsometric data, luminescence spectra and results of preliminary studies of second‐harmonic generation in thes

ISSN:1057-9257    

DOI:10.1002/amo.860020607

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY

ISSN:1057-9257    

DOI:10.1002/amo.860020601

出版商:John Wiley&Sons Ltd.    

年代:1993

数据来源: WILEY