THE INTERACTION OF CU ATOMS WITH THE SI(111)-3-ROOT-X3-ROOT-AG SURFACE

The room-temperature deposition of Cu onto the. Si(lll)-root 3 x root 3-Ag surface has been studied by means of LEED-AES-RBS techniques. As the Cu deposition increases, the root 3 x root 3 LEED pattern is chang ed into a Ix I pattern at a thickness of about 4 ML, which disappears at about 10 ML. An ordered structure of(1 x 1)R30 degrees appears at i s ML, In AES spectra, the intensity of the Si signal decreases with in creasing Cu deposition, while the Ag signal does not change at all aft er an initial small decrease at. 1 ML. The RBS-channeling measurement shows that Cu atoms are situated at an interstitial site at a Cu cover age of 1.5 ML. The Si surface peak in the RBS-channeling spectra incre ases linearly with the Cu coverage in a proportion of Cu/Si = 3/1, The se results indicate that Cu atoms deposited onto the Si(lll)-root 3 x root 3-Ag surface at the initial stage up to 4 ML are buried at an int erstitial sire in subsurface layers of the Si substrate and that a fil m of Cu,Si is formed at higher coverages.