Abstract:

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)-($ \sqrt{7}\times \sqrt{7} $ )(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 Al₂Ge surface alloy, except the SRT7 pure germanene on Al₂Ge, could re-produce the experimental scanning tunneling microscopy images. The relatively stable Al–Ge alloy species are the Al₃Ge₅ BHS-2T, Al₃Ge₅ TRP-2T, and Al₃Ge₃ SRT7-1T on Al (111) while they are the Al₄Ge₄ BHS-1T, Al₃Ge₅ TRP-2T, and Al₂₇Ge₂₇ SRT7-(3 × 3)-9T on Al₂Ge (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 Al₃Ge₅ BHS-2T and Al₄Ge₄ BHS-1T are the most stable alloy sheets on Al (111) and Al₂Ge, 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).

Key words: first-principles calculation, alloyed two-dimensional material, substrate for two-dimensional material growth, two-dimensional nanostructure