Prof. Dr. Joachim Mayer

Phase-change materials are the basis for next-generation memory devices and reconfigurable electronics, but fundamental understanding of the unconventional kinetics of their phase transitions has been hindered by challenges in the experimental quantification. Here we obtain deeper understanding based on the temperature dependence of the crystal growth velocity of the phase-change material AgInSbTe, as derived from laser-based time-resolved reflectivity measurements. We observe a strict Arrhenius behaviour for the growth velocity over eight orders of magnitude (from ~10 nm s⁻¹to ~1 m s⁻¹). This can be attributed to the formation of a glass at elevated temperatures because of rapid quenching of the melt. Further, the temperature dependence of the viscosity is derived, which reveals that the supercooled liquid phase must have an extremely high fragility (>100). Finally, the new experimental evidence leads to an interpretation, which comprehensively explains existing data from various different experiments reported in literature.

28 August 2018 in Inorganic Chemistry

Journal Article

Controlled Crystal Growth of Indium Selenide, In₂Se₃, and the Crystal Structures of α-In₂Se₃

In₂Se₃ has been known for over 100 years and recently attracted interest as a promising candidate for a variety of applications, such as solar cells, photodiodes, and phase-change memories. Despite the broad concern for possible uses, its polymorphism and structure are poorly characterized. By combining X-ray diffraction, transmission electron microscopy, and quantum-chemical calculations, we present here the crystal structures of two layered room-temperature polytypes: 3R and 2H In₂Se₃. Both polymorphs are stacking variants of the same Se–In–Se–In–Se layers comprising two coordination environments for the In atoms, one tetrahedral and one octahedral. By using chemical-bonding analysis, we look at the different In positions in α-In₂Se₃ and compare them to those in the metastable β-phase.

28 October 2010 in Chemistry of Materials

Journal Article

Behavior of Ba(Co, Fe, Nb)O_3-δ Perovskite in CO₂-Containing Atmospheres: Degradation Mechanism and Materials Design

Jianxin Yi

Michael Schroeder

Thomas E. E. Weirich

Joachim Mayer

About Me

Prof. Dr. Joachim Mayer received his Diploma degree in physics from the University of Stuttgart in 1984 and his Ph.D. degree in physics from the Max-Planck-Institut für Metallforschung, Stuttgart, Germany, in 1988. After completing the Ph.D. degree, he joined the Materials Department at the University of California Santa Barbara, Santa Barbara, as a Postdoctoral Research Associate. In 1990, he moved back to the Max-Planck-Institut für Metallforschung, where he worked as a Research Scientist and Group Leader of “Analytical Electron Microscopy” in the Department of Prof. M. Rühle. In 1999, he moved to RWTH Aachen University, Aachen, Germany, to become Professor and Head of the Central Facility for Electron Microscopy. He is now the Head of the Central Facility for Electron Microscopy (GFE) at RWTH Aachen University and the director of the Ernst-Ruska Centrum at Forschungszentrum Jülich. His research focuses on the application of new methods in electron microscopy in the areas of materials science, nanoelectronics, and energy systems.

Prof. Dr. Joachim Mayer

Prof. Dr. Joachim Mayer

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