New Approaches to Atomic-Resolution Structural Analysis by Analytical Scanning Transmission Electron Microscopy*

Over the last two decades, we have witnessed a paradigm change in the way we characterize materials using electron microscopy, starting with the first implementation of aberration correctors followed by faster, more sensitive CMOS detectors, monochromated electron sources for electron spectroscopy and, most recently, magnetic field-free lenses. As the result of these transformational discoveries, we are now able to study materials with unprecedented resolution, sensitivity and precision.

Here, I will discuss several examples where such atomic-resolution characterization and first-principles modeling can be used to unravel the structure-property relationships of materials with potential applications in high-efficiency photovoltaic devices, rechargeable batteries or ceramic thin film devices. Multi-valent battery cathode materials will be characterized under different charge and discharge conditions. We will demonstrate how the intercalation of Mg or Ca ions alters the surface structure of the particles depending on their mobility within the spinel framework. The use of model cathodes based on epitaxial thin films to systematically unravel these changes in surface structures will be discussed.  

In CdSeTe thin-film photovoltaic device, interfaces are important in determining the overall device performance. Using atomic-resolution analysis and novel approaches,  such as 4D-STEM or EBIC measurements, we will demonstrate the effects of grain boundaries, interfacial passivation and carrier-selective contacts on the structure, composition and device performance.