Switching mechanisms in metastable multilayer systems

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Telluride-based phase change materials (PCM) for non-volatile data storage form an intensive and interdisciplinary research field. In the past, homogeneous thin films of the Ge-Sb-Te system were the focus of research, which can be reversibly switched between an amorphous and a crystalline phase by heat, application of a voltage pulse or by irradiation with laser pulses. This phase change is accompanied by strong changes in the optical and electrical properties that can be easily read out. In the present application, we will focus on two novel phase change systems, namely amorphous and crystalline multilayer composites, which, in contrast to the established materials, still offer numerous starting points for basic research at the highest level. In the case of crystalline multilayer systems (so-called iPCM), a particularly energy-efficient switching mechanism is discussed, which is related to structural changes at the interfaces of the crystalline components. However, it has not yet been possible to experimentally verify existing theories regarding the switching mechanism. In this project, Sb2Te3 and GeTe or the new Ge4Se3Te are to be deposited as components of the multilayers for both phase change systems by pulsed laser ablation (PLD). The materials should be switched optically, electrically and by heating and characterized both structurally and functionally. The goal is here e.g. to identify structural changes at different switching times and to derive possible switching mechanisms from these data. In order to achieve these goals, measurement setups for electrical switching and for determining the electrical properties have to be constructed, as well as lithographic methods for structuring the samples have to be designed. A synergistic combination of ex situ and in situ methods with a focus on transmission electron microscopy and X-ray diffraction should cover possible switching mechanisms on different length scales so that structure-property relationships can be deduced.