In situ probing of structural transformations in nanostructured Au–Ge by correlative electron microscopy and calorimetry

We designed an experimental setup that combines Fast Differential Scanning Calorimetry (FDSC) and scanning electron microscopy (SEM) to enable correlative investigations of structural changes and phase transformations, along with their associated changes in thermal and kinetic properties. This is done by installing a FDSC sensor inside the chamber of an environmental SEM (ESEM). Advantages of this correlative technique are demonstrated on the example of a glass-forming binary Au–Ge eutectic alloy. It is shown that neither the microstructure changes observed via SEM nor the DSC curve alone comprise a complete representation of the system's structural, morphological and compositional variations. Via correlative FDSC/ESEM it is, however, possible to identify in a very short time the regions of interest that deserve further investigations, for example via transmission electron microscopy (TEM) and ex situ FDSC. In this way, we are able to analyze in detail the glass transition, the activation energies of the involved phase transformations, the microstructure evolution between metastable and stable phases, and the system's metastable and equilibrium melting temperatures.