Switching mechanisms in metastable multilayer systems

用于非易失性数据存储的碲基相变材料（PCM）形成了一个密集的跨学科研究领域。过去，Ge-Sb-Te系统的均匀薄膜是研究的重点，它可以通过加热、施加电压脉冲或激光脉冲照射在非晶相和晶相之间可逆地切换。这种相变伴随着光学和电学性质的强烈变化，这些变化可以很容易地读出。在目前的应用中，我们将重点关注两种新的相变系统，即非晶和结晶多层复合材料，与现有材料相比，它们仍然为最高水平的基础研究提供了许多起点。在晶体多层系统（所谓的iPCM）的情况下，讨论了一种特别节能的开关机制，这与晶体组件界面的结构变化有关。然而，还不可能通过实验验证现有的关于开关机制的理论。在本项目中，Sb2Te3和GeTe或新的Ge4Se3Te将通过脉冲激光烧蚀（PLD）沉积作为两种相变系统的多层组件。该材料应通过光学、电和加热进行切换，并具有结构和功能特征。这里的目标是识别不同切换时间的结构变化，并从这些数据中推导出可能的切换机制。为了实现这些目标，必须构建用于电气开关和确定电气特性的测量装置，以及用于构造样品的光刻方法。以透射电子显微镜和x射线衍射为重点的非原位和原位方法的协同组合应该涵盖不同长度尺度上可能的开关机制，以便可以推断出结构-性质关系。

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.