AR-ION IMPACT DESORPTION OF AU AND AG FROM THE SI(111)-(2-ROOT-3X2-ROOT-3)-(AU,AG) SURFACE()

The change of Au and Ag coverages at the Si(111)-(2 root 3 x 2 root 3) -(Au,Ag) surface by 5 keV Ar+-ion bombardment has been measured by mea ns of AES and RES techniques in order to determine the potential barri er heights for their desorption and recoil implantation. The cross-sec tion for recoil implantation of Au is 2.5 times larger than that of Au at the Si(111)-(root 3 x root 3)-Au surface, while that of Ag is smal ler than that of Ag at the Si(111)-(root 3 x root 3)-Ag surface. The c ross-section for desorption of Au is also larger than that at the Si(1 11)-(root 3 x root 3)-Au surface, and that of Ag is smaller than that at the Si(111)-(root 3 x root 3)-Ag surface. It is concluded from the recoil-implantation cross-section data that Ag atoms are located on th e Au layer of the double-layer structure. From the analysis of these c ross-sections, the potential barrier heights for recoil-implantation a nd desorption are evaluated to be 4.2 +/- 0.4 and 4.2 +/- 0.8 eV for A u and 0.33 +/- 0.17 and 3.6 +/- 0.7 eV for Ag. (C) 1997 Elsevier Scien ce B.V.