Theoretical studies on alloying of germanene supported on Al(111) substrate

Using density functional theory,we study the alloying of the buckled hexagonal germanene superlattice supported on Al（111）-（3×3）,the sheet composed of triangular,rhombic,and pentagonal motifs on Al（111）-（3×3）,and the buckled geometry on Al（111）-（■）(19°),which are denoted,respectively,by BHS,TRP,and SRT7,to facilitate the discussion in this paper.They could be alloyed in the low doping concentration range.The stable configurations BHS,TRP,and SRT7 of the pure and alloyed germanenes supported on both Al（111） and its Al;Ge surface alloy,except the SRT7 pure germanene on Al;Ge,could re-produce the experimental scanning tunneling microscopy images.The relatively stable AlGe alloy species are the Al;Ge5 BHS-2 T,Al;Ge;TRP-2 T,and Al;Ge;SRT7-1 T on Al（111） while they are the Al;Ge;BHS-1 T,Al;Ge;TRP-2 T,and A127 Ge27 SRT7-（3×3）-9 T on Al;Ge（the n in the nT means that there are n Ge atoms per unit which sit at the top sites and protrude upward）.In addition,the Al;Ge;BHS-2 T and Al;Ge;BHS-1 T are the most stable alloy sheets on Al（111） and Al;Ge,respectively.Comparing with the experimental studies,there exists no structural transition among these alloyed configurations,which suggests that the experimental conditions play a crucial role in selectively growing the pure or the alloyed germanene sheets,which may also help grow the one-atomic thick honeycomb structure on idea Al（111）.