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Kreis ohne Meister : Stefan Georges Nachleben

Das postsowjetische Universitätswesen zwischen nationalem und internationalem Wandel : die Entwicklung der regionalen Hochschule in Russland als Gradmesser der Systemtransformation

1-D chalcogenide nanomaterials for electronics [electronic resource] : phase-change memory and topological insulators

Chalcogenides are ubiquitous in academia and industry. We focus on chalcogenides for phase-change memory and topological insulators. Phase change memory (PCM) utilizes the resistivity contrast between the crystalline and amorphous phases of certain chalcogenides to store information. Industry is making progress in PCM, which could someday compete with flash memory due to its superior scalability, fast switching and high endurance. In contrast, the field of topological insulators is very young. Topological insulators, bulk insulators with conductive surface states, have attracted great attention since their discovery five years ago. They have exotic properties and are exciting for both fundamental studies and potential applications. Our studies of chalcogenide nanomaterials for PCM and topological insulators provided new insights into these fascinating materials. We developed a method to switch PCM cells inside a transmission electron microscope (TEM), allowing direct correlation of electrical behavior with structural changes. Using this technique, we found that the electrical behavior of Ge2Sb2Te3 lateral phase-change cells depends strongly on the highly variable microstructure of the amorphous domain. In search of new PCM materials, we developed the VLS synthesis of GeTe and Sb2Te3 phase-change nanowires. In situ TEM observation of these nanowires revealed a new switching mechanism via the opening and closing of voids. We also synthesized single-crystalline topological insulator nanoribbons, whose large surface to bulk conduction ratio increases the relative contribution of the surface states. We successfully measured Aharonov-Bohm oscillations in the nanoribbons, thereby observing one of the first electrical signatures of the topological states in this material system.