The interaction of Cu atoms with the [formula omitted] surface

Abstract

The room-temperature deposition of Cu onto the Si(111)- 3 × 3 - Ag surface has been studied by means of LEED-AES-RBS techniques. As the Cu deposition increases, the 3 × 3 LEED pattern is changed into a 1 × 1 pattern at a thickness of about 4 ML, which disappears at about 10 ML. An ordered structure of (1 × 1)R30° appears at 18 ML. In AES spectra, the intensity of the Si signal decreases with increasing Cu deposition, while the Ag signal does not change at all after an initial small decrease at 1 ML. The RBS-channeling measurement shows that Cu atoms are situated at an interstitial site at a Cu coverage of 1.5 ML. The Si surface peak in the RBS-channeling spectra increases linearly with the Cu coverage in a proportion of Cu Si = 3 1 . These results indicate that Cu atoms deposited onto the Si(111)- 3 × 3 - Ag surface at the initial stage up to 4 ML are buried at an interstitial site in subsurface layers of the Si substrate and that a film of Cu 3Si is formed at higher coverages.