Microscopic Study of the Spinodal Decomposition of Supported Eutectic Droplets During Cooling: PtGe/Ge{110}

We embarked on an in situ low-energy electron microscopy, photo-electron emission microscopy, and selected area low-energy electron diffraction study during the cooling of huge eutectic droplets through the critical stages of the eutectic transition. On this journey through uncharted waters, we revealed an expected initial shrinking of the exposed area of the droplet, followed by an unanticipated expansion. We attribute this behavior to an initial fast amorphization of the interface between the droplet and surface, followed by the recrystallization of Ge expelled from the droplet at the interface. As a major surprise, we discovered the emergence of extensive spaghetti-like patterns, which are rationalized in terms of parallel Ge ripples oriented along, mainly, [-554] and [-55-4] directions. They emerge during spinodal decomposition when passing the eutectic temperature of the system. Their sides are defined by Ge{111} and Ge{11-1} vicinals covered with Pt-modified (root 3 x root 3) superstructures. The distance between adjacent ripples is about 18 nm.

Automated summary

In this study, we utilize various techniques to investigate the critical stages of cooling of large eutectic droplets. The changes in droplet surface area and unexpected transformations in the internal structure are observed. Additionally, spaghetti-like patterns are discovered during the process when the eutectic temperature is exceeded.