AR-QUASI-5X5-CU AND CU( ION IMPACT DESORPTION OF CU AND AG FROM THE SI(111))SI(111)-ROOT-3X-ROOT-3-AG SURFACES/

The concentration changes of Cu and Ag coverages at the Cu/Si(111)-roo t 3x root 3-Ag and Si(111)-quasi-5x5-Cu surfaces by 5 keV Ar+ ion bomb ardment have been measured by means of AES and Rutherford backscatteri ng (RES) techniques in order to determine the cross-sections for their desorption and recoil-implantation We have evaluated the potential ba rrier heights for desorption and recoil-implantation from the obtained cross-sections. The potential barrier height for desorption of Ag ads orbates is in accordance with the sublimation energy of Ag metal, and the potential barrier height for recoil-implantation of Ag is consiste nt with that for the Si(111)-root 3x root 3-Ag surface. Together with the observed root 3x root 3 LEED pattern For the Cu/Si(111)-root 3x ro ot 3-Ag surface, these results suggest that Ag atoms are accommodated at the top-most surface layer as the Si(111)-root 3x root 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 at oms are buried and located al an interstitial site in the surface laye r of the Cu/Si(111)-root 3x root 3-Ag surface. It is also found that t he Si(111)quasi-5x5-Cu structure is easily destroyed by Ar+ ion bombar dment.