First-principles study of the stability of free-standing germanene in oxygen

TL;DR

This study uses first-principles calculations to compare the stability of free-standing germanene and silicene in oxygen, revealing germanene's higher stability and potential for oxide formation.

Contribution

It provides the first detailed comparison of oxygen interaction with germanene versus silicene, highlighting germanene's greater stability and different adsorption behaviors.

Findings

Germanene is more kinetically stable than silicene against oxygen dissociation.

Oxygen molecules can stably adsorb on germanene surface.

Oxygen atoms are less mobile on germanene, favoring oxide formation.

Abstract

The O2 dissociation and O atoms adsorption on free-standing germanene are studied by using first-principles calculations in this letter. Compared with the spontaneous dissociation of oxygen molecule on free-standing silicene in air, germanene is more stable than silicene from kinetic point of view, with overcoming energy barrier of about 0.55 eV. Especially, in contrast with the unique chemical adsorption of O2-dissociation-induced O atoms on silicene, oxygen molecule can behave a correspondingly stable adsorption on germanene surface. Moreover, single O atom adsorption on germanene is also different to that on silicene, resulting in two opposite migration pathways on germanene surface. Furthermore, once the oxygen molecule dissociates into O atoms on germanene surface, the migration and desorption of O atoms are relatively difficult under room temperature due to the strong Ge-O bonds in the O-adsorbed germanene, in favor of forming germanium oxides. The results provide compelling evidence to show that free-standing gemanene is relatively stable in oxygen,which is different to silicene essentially.