MatWerk – serie

Christian Rockenhäuser adresses phase formation and cation interdiffusion of the GdxCe1-xO2-x/2-and SmxCe1-xO2-x/2-material systems at temperatures ranging from 970 to 1270°C. Diffusion couples with CeO2/Sm2O3 and CeO2/Gd2O3 interfaces were fabricated for the investigations. The resulting reaction phases were investigated utilizing transmission electron microscopy (TEM) and allow conclusions regarding the phase diagrams in the examined temperature range. A miscibility gap can be ruled out for GdxCe1-xO2-x/2 across the whole composition range. Cation interdiffusion coefficients were determined for both material systems by measuring and evaluating concentration profiles at the material interfaces. The activation enthalpies for interdiffusion were calculated using the temperature dependence of the interdiffusion coefficients. The study for the first time compiles comprehensively the previous results regarding the phase diagrams of the two material systems since 1923.

Denise Reichel studies the delicate subject of temperature measurement during lamp-based annealing of semiconductors, in particular during flash lamp annealing. The approach of background-correction using amplitude-modulated light to obtain the sample reflectivity is reinvented from rapid thermal annealing to apply to millisecond annealing. The author presents a new method independent of the lamp operation to obtain this amplitude modulation and derives a formula to describe the process. Further, she investigates the variables of the formula in depth to validate the method’s suitability for background-corrected temperature measurement. The experimental results finally proof its power for elevated temperatures.

Christian Pauly demonstrates the strong topological properties of the technologically relevant phase change materials Sb2Te3 and Ge2Sb2Te5 by using two powerful techniques for mapping the surface electronic structure: scanning tunneling spectroscopy (STS) and angle-resolved photoemission spectroscopy (ARPES). In the case of a phase change material, this opens up the possibility of switching between an insulating amorphous and a conducting topological phase on nanosecond-time scales. Moreover, the author presents first experimental results of a weak topological insulator, namely on the bismuth-based graphene-like sheet system Bi14Rh3I9, revealing a topologically protected one-dimensional edge channel as its fingerprint. The edge state is as narrow as 0.8 nm, making it extremely attractive to device physics. Those strong and weak topological insulators are a new phase of quantum matter giving rise to robust boundary states which are protected from backscattering and localization.

Frieder Ostermaier legt Forschungsergebnisse zum Aufbau von Biosensoren mit Kohlenstoffnanoröhren dar, die sich aufgrund ihrer geometrischen, chemischen und elektrischen Eigenschaften hervorragend als sensitives Element und als Template eignen. So wird, neben der Sortierung von Kohlenstoffnanoröhren nach elektronischem Typ durch Gel-Chromatographie, eine effiziente und detaillierte Charakterisierung von Kohlenstoffnanoröhren-Dispersionen mittels UV-Vis-Spektroskopie gezeigt. Zudem wird eine Möglichkeit der eindimensionalen Funktionalisierung von Biomembransensoren mittels Selbstassemblierung vorgestellt.

Based on the current state of the art Marcus Lau demonstrates an improved experimental design for defined laser irradiation of particles in liquid environment. The experimental results achieved with the designed reactor demonstrate how particle properties can be modified by defined laser energy dose input. By utilizing different model materials new insights into laser processing of particles in liquids are gained that allow an enhanced process understanding.