Decagonal structure of Al72Ni20Co8 studied by atomic-resolution electron microscopy

Abstract We study the atomic structure of an Al 72 Ni 20 Co 8 decagonal quasicrystal by a complementary use of conventional high-resolution transmission electron microscopy (HRTEM) and annular dark-field scanning transmission electron microscopy (ADF-STEM). The chemical ordering of the structure is derived from atomic-resolution ADF-STEM with Z -contrast ( Z is the atomic number), highlighting the heavy atom positions. Details on the total atomic arrangements, including the relatively light constituent elements, are examined by HRTEM with phase contrast. The present results demonstrate that a combination of HAADF-STEM and HRTEM is quite powerful for complicated intermetallic structures, enabling a reliable structural analysis to be made based on electron microscopy.