%0 Journal Article
%T Tunable Electronic and Topological Properties of Germanene by Functional Group Modification
%A Ceng-Ceng Ren
%A Chang-Wen Zhang
%A Pei-Ji Wang
%A Ping Li
%A Shu-Feng Zhang
%A Wei-Xiao Ji
%J Archive of "Nanomaterials".
%D 2018
%R 10.3390/nano8030145
%X Electronic and topological properties of two-dimensional germanene modified by functional group X (X = H, F, OH, CH3) at full coverage are studied with first-principles calculation. Without considering the effect of spin-orbit coupling (SOC), all functionalized configurations become semiconductors, removing the Dirac cone at K point in pristine germanene. We also find that their band gaps can be especially well tuned by an external strain. When the SOC is switched on, GeX (X = H, CH3) is a normal insulator and strain leads to a phase transition to a topological insulator (TI) phase. However, GeX (X = F, OH) becomes a TI with a large gap of 0.19 eV for X = F and 0.24 eV for X = OH, even without external strains. More interestingly, when all these functionalized monolayers form a bilayer structure, semiconductor-metal states are observed. All these results suggest a possible route of modulating the electronic properties of germanene and promote applications in nanoelectronics
%K germanene
%K functional group
%K external strain
%K topological insulator
%U https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5869636/