Fundamental properties of transition-metal-adsorbed germanene: a DFT study

The transition-metal-doped germanene can greatly diverse electronic and magnetic properties. Fe-doped germanene exhibits a semiconductor nature with a very large magnetic moment at the four possible absorption sites, the Co-Ge compound demonstrates a metallic nature with a smaller magnetic moment. Co absorption also presents semiconducting nature but does not possess magnetism in any of the absorption sites. The transition-metal-Ge bondings exhibit a very complex multi-orbital hybridization. This hybridization can be easily observed through the results of the charge distribution and projected atom-, spin-, and orbital-decomposed density of states. Moreover, there is clearly a charge transfer from Ge to TM atoms, which weakens the strength of Ge–Ge bonds and shows that TM-Ge bonds are formed mainly performing ionic character. Very interestingly, comparing TM atoms doped-germanene with such systems in silicene and graphene, the absorbed energy values showed that germanene might be the best candidate to accommodate TM atoms among all three 2D materials. Moreover, the recent results about the successful synthesis of adatom-doped graphene as well as the creation of pristine germanene in the free-standing state have paved the way for germanene and functionalized germanene compounds to be applied to the manufacture of practical devices.