Synthesis of Xenes: physical and chemical methods

Since the debut of silicene in the experimental stage more than a decade ago, the family of two-dimensional elementary layers beyond graphene, called Xenes or transgraphenes, has rapidly expanded to include elements from groups II to VI of the periodic table. This expansion has opened pathways for the engineering of elementary monolayers that are inherently different from their bulk counterparts in terms of fundamental physical properties. Common guidelines for synthesizing Xenes can be categorized into well-defined methodological approaches. On the one hand, bottom-up methods, such as physical epitaxial methods, enable the growth of monolayers, multilayers, and heterostructured Xenes. On the other hand, top-down chemical methods, including topotactic deintercalation and liquid-phase exfoliation, are gaining prominence due to the possibility of massive production. This review provides an extensive view of the currently available synthesis routes for Xenes, highlighting the full range of Xenes reported to date, along with the most relevant identification techniques.