Ar+ ion impact desorption of Cu and Ag from the Si(111)-quasi-5 × 5-Cu and surfaces

Abstract The concentration changes of Cu and Ag coverages at the Cu Si (111) -√3 × √3- Ag and Si(111)-quasi-5 × 5-Cu surfaces by 5 keV Ar+ ion bombardment have been measured by means of AES and Rutherford backscattering (RBS) techniques in order to determine the cross-sections for their desorption and recoil-implantation. We have evaluated the potential barrier heights for desorption and recoil-implantation from the obtained cross-sections. The potential barrier height for desorption of Ag adsorbates is in accordance with the sublimation energy of Ag metal, and the potential barrier height for recoil-implantation of Ag is consistent with that for the Si(111)-√3 × √3-Ag surface. Together with the observed √3 × √3 LEED pattern for the Cu Si (111) -√3 × √3- Ag surface, these results suggest that Ag atoms are accommodated at the top-most surface layer as the Si(111)-√3 × √3-Ag surface. On the other hand, the cross-section for desorption of Cu is smaller than that of Ag, which leads to rather high potential barrier height, and the cross-section for recoil-implantation is considerably larger than that of Ag. For these results, we propose a hypothesis that Cu atoms are buried and located at an interstitial site in the surface layer of the Cu Si (111) -√3 × √3- Ag surface. It is also found that the Si(111)-quasi-5 × 5-Cu structure is easily destroyed by Ar+ ion bombardment.