Ferecrystals
Ferecrystals (FCs) are a class of layered materials consisting of atomically thin layers of a transition metal dichalcogenides (TMDC) stacked alternately with metal monochalcogenide layers. Introduction The general formula of ferecrystals is [(MX)1+δ]m[TX2]n, where X is Se or Te, M a metal, T a transition metal, and δ represents the crystallographic misfit between the MX and TX2 layers. Ferecrystals are characterized by turbostratic disorder, which refers to an apparently random rotation of MX and TX2 layers around their crystallographic c-axes and between grains within the layer plane, while maintaining parallel c-axes to the stacking direction. Despite the disorder, continuous layers of composition TX2 and MX are usually maintained across grain boundaries throughout the ferecrystal sample. The name "ferecrystals" comes from the Latin word "fere," meaning "almost," referring to the turbostratic disorder and grain-like structure. Growth Ferecrystals can be prepared using the Modulated Elemental Reactants (MER) method. Developed by David C. Johnson and his team at the University of Oregon, this technique allows for the creation of ferecrystals of arbitrary n and m, unlike commonly used synthesis techniques. The MER method involves physical vapor deposition (PVD) of individual monoatomic layers followed by annealing of the deposited precursors. During annealing, self-assembly of