Charge attachment induced transport (CAIT) studies of energy landscapes in ion conducting solids (Quantification of populated site energy distribution in amorphous and crystalline materials)

固体材料中可移动离子的势能分布与原子尺度结构密切相关，并决定着离子输运等功能。在FOR5065研究单元的这个项目P1中，用电荷附着诱导输运(CAIT)和飞行时间二次离子质谱仪(ToF-SIMS)技术相结合的方法研究了离子导电固体的势能分布。我们的目标是确定固体中的格位能量分布作为结构有序的函数，即非晶态、晶态和双晶态。作为具有模型特征的材料，重点将放在硼酸锂和钛酸锶及其衍生物上。在CAIT技术中，碱性离子附着到样品上，导致表面充电，伴随的电化学势梯度和样品内相应电荷载流子的传输。来自离子束的外来离子在样品内部的传输方向上耗尽并取代本机离子，从而产生浓度深度分布。浓度分布被冻结，然后用TOF-SIMS进行定量分析，并利用Nernst-Planck-Poisson(Nernst-Planck-Poisson)输运理论进行模拟。最初，分析是为了得到实验点的能量分布(SED)和SED的填充部分(PSED)。这些是从理论(P5 Maass和P6 Jacob)转移到协作伙伴的。稍后，项目P5和P6将返回理论SED和PSED，作为该项目P1(Weitzel)内的NPP分析的输入。同时，样品也被转移到合作伙伴Volkert(P3)进行原子探针断层扫描(APT)和Jooss(P4)进行透射电子显微镜(TEM)以进行详细的原子结构分析。此外，样品被转移到Vogel(P2)基团进行核磁共振研究。后者产生的关联分布将直接与本项目中确定的空间相关扩散系数的分布进行比较。最终，这项工作有望有助于更好地理解离子导电固体中的势能格局及其与原子结构和宏观输运函数的相互关系。

The potential energy landscape of mobile ions in solid-state materials and the atomic scale structure are intimately interrelated and determine the function, e.g. ion transport. Within this project P1 of the research unit FOR5065 the potential energy landscape of ion conducting solids is investigated by a combination of the charge attachment induced transport (CAIT) and the time-of-flight secondary ion mass spectrometry (ToF-SIMS) techniques. The goal is the determination of site energy distributions in the solid as a function of the structural order, i.e. for amorphous, crystalline and bicrystalline states. As materials with model character the focus will be on lithium borates and strontium titanate and derivatives thereof. Within the CAIT technique alkali ions are attached to the samples leading to a charging up of the surface, the concomitant gradients of the electrochemical potential and the transport of the respective charge carrier within the sample. Foreign ions from the ion beam deplete and replace native ions in the direction of transport inside the sample causing concentration depth profiles. The concentration profiles are frozen and subsequently quantitatively analyzed by ToF-SIMS and modelled by means of the Nernst-Planck-Poisson NPP) transport theory. Initially the analysis is elaborated to yield experimental site energy distributions (SED) and populated parts of the SED (PSED). These are transferred to collaboration partners from theory (P5 Maass and P6 Jacob). Later, projects P5 and P6 will return theoretical SED and PSED as input for the NPP analysis within this project P1 (Weitzel). In parallel, the samples are also transferred to collaboration partner Volkert (P3) for atom probe tomography (APT) and Jooss (P4) for transmission electron microscopy (TEM) for detailed atomistic structure analysis. Furthermore, the samples are transferred to the Vogel (P2) group for NMR studies. The latter leads to a distribution of correlation which will be directly compared to the distribution of spatially dependent diffusion coefficients determined within this project.Ultimately, this work is expected to lead to an improved understanding of the potential energy landscape in ion conducting solids and its interrelation with atomistic structure and macroscopic transport function.