Surface atomic structure of alloyed Mn5Ge3(0 0 0 1) by scanning tunneling microscopy

Surface atomic structure of Mn5Ge3(0 0 0 1) is studied by scanning tunneling microscopy. Hexagonal honeycomb ordering is observed at high energy levels, ∣E − EF∣ ∼ 1.2 eV, on the flat regions of three-dimensional Mn5Ge3 islands. At low energy levels, ∣E − EF∣ ∼ 0.5 eV, however, atomic images exhibit dot-array and ring-array structures, which show complete and partial contrast inversion, compared to the honeycomb ordering. Experimental observations are discussed on the basis of possible atomic models.