Detecting and Measuring Interface Chemistry to Correlate With Interface Properties: Can Interfaces be “Clean”?

ABSTRACT The structure and chemistry of interfaces influence material properties, yet distinguishing “clean” from “contaminated” interfaces remains challenging. This work examines strategies for detecting and quantifying interfacial chemistry to assess whether interfaces can be considered “clean.” We discuss the concept of Gibbsian adsorption and demonstrate how solute enrichment, structural disorder, and chemical excess interact to define interface behavior. Approaches on how to utilize advanced transmission electron microscopy and spectroscopy techniques are reviewed to determine interfacial excess in atoms/nm 2 . Quantification of interfacial chemical excess, accounting for statistical confidence, is discussed within the framework of the spatial difference technique. We conclude that while new microscopy tools offer unprecedented sensitivity, an experimentally determined null excess can at best be described as a quantity that falls below the experimentally determined detection limit. Structural disordering may also be represented as an interfacial excess quantity. The notion of a completely “clean” interface is conceptually and experimentally untenable.