Christiane Ziegler

Interface analysis of the system Si/YBa2Cu3O7-x

SummaryThe influence of different preparation conditions and substrate surface orientations on the superconducting properties of thin YBa2Cu3O7−x (YBCO) films on silicon was studied. Comparative electrical and surface spectroscopic measurements were performed. SAM and SIMS depth profile analysis show an enrichment of barium at the interface between the superconductor and silicon for samples with Tc<76 K. Comparison with XPS data obtained for thin silicon films on YBCO indicates the formation of barium and yttrium silicates at the interface under these conditions.

Preparation of highly ordered quinquethiophene thin films on TiO2 substrates

To understand the intrinsic electrical properties of conjugated polymers in general and of oligothiophenes in particular, ultra-pure and highly ordered thin films or single crystals are required. In this context, studies on thin films of quinquethiophene (α5T) prepared by evaporation in UHV were performed. As substrates insulating and conducting oxides such as different single crystal surfaces of TiO2 were chosen. The latter are particularly interesting because TiO2 can be doped to be n-conducting. These substrates may therefore be used for hybrid inorganic–organic thin film pn-diodes. Here, we report on SFM-measurements under ambient conditions, which show that the deposition of α5T from a Knudsen cell under UHV conditions leads to cluster growth on TiO2(011) and to ordered layers on undoped TiO2(001). On doped TiO2(001) the growth mode is largely influenced by the surface roughness, i.e. the presence of pinning centers. It could be shown that the α5T molecules on TiO2(001) are oriented with their long axis mainly perpendicular to the substrate plane and form two complete monolayers (Frank–Van der Merwe growth mode) before the growth mode changes to a simultaneous multilayer growth, in line with earlier experiments using other oxidic substrates.

X-ray photoelectron spectroscopy of KrF laser-irradiated polycarbonate films

Abstract Spun films of polycarbonate were photoablated in air at 248 nm. The etch and incubation data have a superlinear dependence on the laser fluence. The surface compositional changes were analysed by X-ray photoelectron spectroscopy (XPS). As evidenced by the decrease of the O/C ratio, photoablation is inferred as distinct from the low-intensity photooxidative degradation. A direct correlation is observed between the XPS and incubation data and the ablation seems to occur by chain scission at the CO bond, the fully incubated surface being an average of monomeric composition.

Präparation definierter Materialien und Strukturen

In allen Anwendungsbereichen spielen definierte Materialien mit hochster chemischer Reinheit und idealer geometrischer Anordnung von Atomen eine zunehmend grosere Rolle. Deren Einsatz ist essentiell fur die Funktionsfahigkeit beispielsweise von mikrostrukturierten Bauelementen der Mikroelektronik oder Sensorik. Entsprechend der grosen Variationsbreite unterschiedlicher Materialien und Strukturen gibt es eine Fulle unterschiedlicher Praparationsverfahren, auf die in diesem Kapitel nur beispielhaft eingegangen werden kann.

Aufbau der Materie im Überblick

In diesem Einfuhrungskapitel wird, ausgehend von klassischen Experimenten zum Aufbau der Materie, das heutige Verstandnis der Struktur von Gasen, Flussigkeiten, Festkorpern und Grenzflachen im ersten Uberblick dargestellt. Die physikalisch-chemischen Ansatze der Thermodynamik, Kinetik, Theorie der chemischen Bindung und statistischen Thermodynamik werden kurz charakterisiert. Anschliesend wird die Gliederung des folgenden Stoffs vorgestellt.

Quantenmechanik und Aufbau der Materie

Die mikroskopische Struktur der Materie last sich prinzipiell mit der Schrodingergleichung beschreiben.