Xenes are atomically thin monoelemental materials, which represent a new paradigm, while their revolutionary properties may be key to unlocking a large gamut of exciting applications (Fig. 1).
The seminal article demonstrating the pionnering realization of silicene by Molecular Beam Epitaxy on a silver (111) crystal surface1 has been followed two years later by a second one, showing, in the same fashion, the first synthesis of germanene in multi-phase domains on a gold substrate4. Single-phase epitaxial germanene obtained in 2018 by the segregation of Ge atoms on top of a thin silver film initially grown on a Ge(111) template has been a new progress and a significant technical evolution5. Correlatively, large area planar stanene was realized on a pre-prepared Ag2Sn surface alloy formed on a Ag(111) substrate6, which has further permitted -by combining both deposition and segregation approaches- to integrate stanene and germanene in unique planar heterostructures7, which is essential for nanoelectronics applications (Fig. 2). Ultimately, plumbene3, the last Group 14 Xene, has been realized on the amazing bubble-like structure of a PbxPd(1-x) surface alloy, the “Nano WaterCube” (Fig. 3).
All these Xenes with semimetallic band structure exhibit some degree of spin–orbit coupling leading to openings of bandgaps around Dirac cones, which increase with their atomic number, possibly giving rise to the realization of the quantum spin Hall effect ; typically, stanene could enable room temperature spintronics8.
Despite significant challenges ahead in this postgraphene era, fundamental research and technological revolutions, will open exciting prospects for Xenes, not only in nanoelectronics and spintronics, but also in other envisaged areas, such as photonics, sensing, thermoelectrics and energy systems9.