Influence of substrate morphology on organic layer growth: PTCDA on Ag(1 1 1)

By UV-excited photoelectron emission microscopy (UV-PEEM) we investigated the microscopic growth behavior of organic thin films using 3,4,9,10-perylene-tetracarboxylicacid dianhydride (PTCDA) on a Ag(1 1 1) single crystal substrate as example. Direct, real time observation allows to correlate the initial growth modes and the related kinetic parameters with substrate properties like terrace width, step density, and step bunches from the submonolayer range up to 5 layers or more. Above room temperature PTCDA grows in a Stranski–Krastanov fashion: after completion of the first two stable layers three-dimensional islands are formed. The nucleation density strongly depends on the temperature and the substrate morphology thus affecting the properties of the organic film.     

Characterization of particles made by desolvation of monodisperse microdroplets of analyte solutions and particle suspensions for nanoparticle calibration in inductively coupled plasma spectrometry

Particles produced by low-temperature desolvation of monodisperse microdroplets of analyte standard solution and nanoparticle suspensions in argon were collected on Si-wafers and studied applying scanning electron microscopy and X-ray microprobe techniques. At desolvation temperatures of about 150 °C, the particles from standard solutions are most often spherical and solid with good reproducibility and the analyte elements together with the unavoidable accompanying elements from trace contamination seem to be homogeneously distributed in the particles. However, there are surprising exceptions, particularly at higher temperatures, where analyte elements are separated in the particle by reduction or crystallization, as shown with Au and Ca standard solutions, respectively. Drying droplets of a diluted suspension of 250 nm gold particles at 200 °C revealed another interesting result, the production of relatively stable concave balloons of ∼ 3 µm in diameter including the Au particles. The balloon sheath was formed of compounds made of the contaminant elements in the suspension. The morphology of the particles is discussed in consideration of the Peclet number, the ratio of evaporation rate to analyte diffusion coefficient. The consequences of particle size and morphology for calibration purposes in nanoparticle characterization by ICP spectrometry are discussed.     

Uniformly ergodic maps onC*-algebras 027

LetT be an identity preserving Schwarz map on aC ^*-algebra. The following conditions are proved to be equivalent: (a)T is uniformly ergodic with finite-dimensional fixed space. (b)T is quasi-compact.     

Ein Verfahren zur Berechnung des charakteristischen Exponenten der Mathieuschen Differentialgleichung. II

Ohne Zusammenfassung     

R2-planes with 3-dimensional automorphism group fixing precisely a line

It is shown that the class of these R²-planes consists of those listed by STRAMBACH 1970, those added by OSTMANN 1975, and those added by GROH 1981. This last class consists of sums of two hyperbola planes. Furthermore, the isomorphism types are determined. All investigations are carried out for the much more general situation of an R²-plane with Δ-invariant screen, Δ ? R².     

Zur Berechnung der Eigenwerte der Sphäroiddifferentialgleichung

Ohne Zusammenfassung