ION IMPACT DESORPTION OF BINARY NOBLE-METAL ADSORBATES ON THE SI (111) SURFACE

The keV Art ion impact desorption technique has been applied to determ ine binding energies of binary noble metal adsorbates at Cu/Si (1 1 1) -root 3 x root 3-Ag, Si (1 1 1)-2 root 3 x 2 root 3-(Au,Ag) and Si (1 1 1)-root 3 x root 3-(Au,Cu) surfaces. Decay profiles of surface cover ages of the binary adsorbates as a function of Ar+ ion fluence were me asured by means of AES and RES techniques. It is shown that the covera ges measured by AES decrease rapidly and those by RES become constant after they decrease at low Ar+ ion fluences. Cross-sections for their recoil-implantation and desorption are determined from the analysis of their decay profiles. Layered structures and locations of the binary metal adsorbates are determined qualitatively from the obtained cross- sections. To analyse them, the most probable collision process is mode lled, and the potential barrier heights for recoil-implantation and de sorption (binding energies) are estimated from the experimental cross- sections. (C) 1998 Elsevier Science B.V.