Recent theoretical and experimental studies have proven that germanium can have stable, single layer honeycomb structures like graphene and it is entitled as germanene. It has been also shown that germanene share several of the exceptional properties of graphene. However, in contrast to suspended graphene which can be easily exfoliated from 3D layered graphite; free-standing single layers of Ge were not synthesized yet, it does not exist as 3D layered bulk phase in nature. Therefore, it is a much accessible way (and the only possible way so far) to synthesize single layers of germanene on suitable substrates. Understanding the structure of layered germanene is of particular importance in a wide range of applications.
In a recent study, Computational Nanoscience team at UNAM revealed that the adsorption of a Ge adatom (for instance during epitaxial growth) on germanene is exothermic and spontaneously constructs a dumbbell structure (DB), where the Ge adatom attached to the topside on germanene pushes the host Ge atom down to form a cage. Even more remarkable is that new phases can be constructed by the periodic coverage of germanene with DBs. Depending on the coverage of DBs, these stable phases can be metal or narrow band gap semiconductors in magnetic or nonmagnetic states, and hence, they attribute diverse electronic and magnetic functionalities to germanene. Dr. Durgun says “Revealing the DB structure on germanene not only help us to clarify the experimental observations but also opens a way to add novel features to germanene for various applications. Our calculations further indicate the possibility of decorating DBs on germanene, though which new phases can grow. This can bring about a new class of single-layer materials and can be precursors of different systems”.
The complete study has been published in Journal of Physical Chemistry Letters and Journal of Physical Chemistry C.