Topotactic synthesis of the overlooked multilayer silicene intercalation compound SrSi2

Abstract

Silicene, a 2D honeycomb lattice of Si atoms similar to graphene, is expected to be a platform for nanoelectronics and home to novel quantum phenomena. Unlike graphene, free-standing silicene is notoriously difficult to stabilize, while strong hybridization of silicene with substrates destroys its desirable properties. On the other hand, Dirac cones of silicene are effectively realized in a bulk – stoichiometric ionic multilayer silicene intercalation compound CaSi₂. Besides, a number of new 2D silicene-based materials are synthesized employing CaSi₂ as a precursor. However, the rather complex atomic structure of CaSi₂ and fresh opportunities of physical and chemical breakthroughs drive the search for alternative compounds with silicene networks. Here, a new polymorph of SrSi₂ is synthesized, enjoying both the structure of intercalated multilayer silicene and the simplest possible stacking of silicene sheets. The MBE-quality synthesis accomplished on Si(001) and Si(111) surfaces leads to epitaxial films of SrSi₂ with orientation controlled by the substrate, as revealed by XRD, RHEED and electron microscopy studies. The structural SrSi₂/Si relation is mirrored in the transport properties of the films.