The change of Au and Ag coverages at the Si(111)-(2√3 × 2√3)-(Au,Ag) surface by 5 keV Ar+-ion bombardment has been measured by means of AES and RBS techniques in order to determine the potential barrier heights for their desorption and recoil implantation. The cross-section for recoil implantation of Au is 2.5 times larger than that of Au at the Si(111)-(√3 × √3)-Au surface, while that of Ag is smaller than that of Ag at the Si(111)-(√3 × √3)-Ag surface. The cross-section for desorption of Au is also larger than that at the Si(111)-(√3 × √3)-Au surface, arid that of Ag is smaller than that at the Si(111)-(√3 × √3)-Ag surface. It is concluded from the recoil-implantation cross-section data that Ag atoms are located on the Au layer of the double-layer structure. From the analysis of these cross-sections, the potential barrier heights for recoil-implantation and desorption are evaluated to be 4.2±0.4 and 4.2±0.8 eV for Au and 0.33±0.17 and 3.6±0.7 eV for Ag. © 1997 Elsevier Science B.V. All rights reserved.