Grain boundaries (GBs) modify the local microstructures, chemical bonding, and carrier transport of polycrystalline materials, influencing their overall mechanical and functional properties. We developed a correlative characterization method by combining several advanced ex-situ and in-situ techniques to reveal the relationship between structure, bonding, and property of individual GBs in metavalently bonded PbS.

Abstract

Grain boundaries (GBs) play an important role in the mechanical and functional properties of polycrystalline materials. For charge carrier transport, GBs can either decrease or even increase the electrical conductivity, depending on the local atomic arrangements at the GB. Yet, uncovering the “one-to-one correlation” between structures and properties is non-trivial. This work demonstrates an advanced approach that combines multiple in-situ and ex-situ techniques to investigate the structural, chemical, and transport properties of individual GBs. Advanced characterization and processing techniques such as electron backscatter diffraction and focused ion beam allow us to site specifically “lift out” individual GBs from the polycrystalline bulk. Combined with semiconductor fabrication protocols such as electron beam lithography and deposition to prepare a measurement circuit, we can obtain the electrical properties of the microscale lamella. Moreover, the chemical composition and bonding mechanism of the same GB can be determined by atom probe tomography. An example of PbS shows that the high-angle GB strongly reduces carrier mobility due to the existence of a potential barrier and the local collapse of metavalent bonding.