RHEED and STM studies of the pseudo-tenfold surface of theξ′−Al77.5Pd19Mn3.5approximant…

International audienceThe pseudo-tenfold surface of the-Al 77.5 Pd 19 Mn 3.5 crystal, an approximant of the icosahedral Al– Pd– Mn quasicrystal, is investigated by reflection high-energy electron diffraction RHEED and scanning tunneling microscopy. The observed RHEED patterns of the surface after sputtering are found to be consistent with those of a simple cubic lattice with 11 ¯ 0 surface plane. The 001 and 110 axes of the surface plane are oriented along the principal low-index axes of the bulk. The RHEED patterns of the sputter-annealed surface consist of diffraction streaks with periodic spacings expected for the bulk truncated surface. The surface prepared under different preparation methods is found to exhibit different step-height distribution and terrace morphology. A longer annealing yields a high density of shallow pentagonal pits on terraces, separated predominantly by 0.80-nm high steps and occasionally by double steps. In contrast, the surface prepared with shorter annealing time exhibits highly perfect terraces with 0.80-nm-high steps and additional unusual steps of heights close to 0.40 nm. All step heights observed for both preparation methods are consistent with interlayer spacings of the bulk model