Technical evolution for the identification of Xenes: from microscopy to spectroscopy

Having the ideal electronic properties and promising applications in various areas, Xenes have been studied intensively as a hot topic from the past decade. From silicene to tellurene, all nine varieties of Xenes have been synthesized and identified successfully by over 10 measurement means. In the incipient stage of Xenes study, in situ scanning tunneling microscopy and angular-resolved photoemission spectroscopy played a dominant role in exploring crystal and electronic structure due to the limited molecular beam epitaxy (MBE) synthetic method and instability of some Xenes (e.g., silicene) in air. In the development of Xenes, more and more Xenes beyond silicene have been synthesized successfully by other methods instead of MBE, which leads involving other identification technological means into Xenes study possible, such as transmission electron microscopy, atomic force microscopy, and in situ Raman. Here, we summarize the technical evolution of Xene researches focusing on both the microscopic and spectroscopic methods.