Scanning tunnelling microscopy with atomic resolution on the twofold surface of the icosahedral AlPdMn quasicrystal

Authors:
Publisher website
Google Scholar
Abstract
We have investigated the 2-fold surface of an icosahedral Al70Pd21Mn9 quasicrystal by means of low-temperature scanning tunnelling microscopy (77 K). The sequence of the terrace step edge heights revealed a Fibonacci sequence with S = 2.40 Å and L = τS = 3.88 Å as fundamental terrace step heights. S and L can be related to the pentagon edge length of the below terrace Bergman polytope and the surface dissected Bergman polytope of the 5-fold surface. The atomic resolution STM images of the 2-fold surface have been compared to the M-model structure of the i-AlPdMn and the experimental STM surface structure of the 5-fold surface by analysis of the FFT spots. We could show that the positions of the FFT spots in the 2-fold surface are related to the FFT spots of the 5-fold surface by projections onto the fivefold axis and are in good correspondence to the model structure. We identified characteristic rectangular features on the 2-fold surface with edge length of 4.8, 7.7 and 12.6 Å corresponding to D2, τD2 and τ 2D2 with D2 being the pentagon edge length of the surface dissected Bergman polytope. We interpret our results as being a strong indication for the bulk termination of the 2-fold surface of the i-AlPdMn quasicrystal.

This publication has 10 references indexed in Scilit: