Surface characteristics of quasicrystalline materials: an overview of work conucted at ames laboratory

摘要

Over the last few years,work in our laboratories in Ames has focussed on elucidating the surface characteristics of Al-based quasicrystalline materials,namely icosahedral(i) Al-Cu-Fe and i-Al-Pd-Mn.Our work inovlves the study of the clean surfaces of these materials under ultrahigh vacuum conditions.We find that surfaces cleaned by Ar~+ sputtering are depleted in Al relative to the bulk composition.single grains,after sputtering,undergo a two-stage regrowth process as they are annealed.After heating to about 600 K,a crystalline overlayer is formed.This is rather abruptly replaced at about 750 K by a surface that appears quasicrystalline within the resolution fo the experimental techniques used.Calculations based on low-energy electron diffraction (LEED) measureemnts of this higher temeprature state indicate that the Al-rich layers in the bulk modle of these materials are the favored surface terminations.Results of low-energy ion scattering (LEIS) corroborate this finding.COnsistent with this,we find that the oxidation behavior and general reactivity of these materials are analogous to pure Al.