Interface formation of W evaporated on Si(111) (7×7)

XPS, XAES, UPS and LEED have been used to study the interface formation of W evaporated onto Si(111) (7×7) surfaces, with samples maintained at room temperature and after subsequent annealing of the deposits. The intensity variations of the core levels (Si 2p and W 4f) and of the Auger signals (Si KLL, Si LVV and W NOO) as a function of surface coverage θ correspond to an abrupt junction and a layer-by-layer growth mode. This hypothesis is confirmed by work function measurements. The W 4 f 7 2 undergoes an energy shift of − 0.4 eV (towards lower binding energy) at low coverage, θ ⪷ 1 monolayer (ML), and reaches its bulk metal value at θ ≈ 10 ML; this shows in addition a rather short transition region. Meanwhile, the only variations observed with Si core levels are energy shifts of −0.2 eV for Si 2p and +0.2 eV for Si KLL, which take place at the very first deposition of a submonolayer amount of W. These shifts are attributed to a surface band bending variation. When the metal deposit attains a surface coverage θ ≈ 0.1 ML the Si characteristic surface states disappear from the UPS spectra, while the (7×7) LEED pattern is replaced by a (1×1) diagram which afterwards vanishes in the background for θ⪸1 ML . UPS indicates a rapid predominance of d-metal emission, and a W valence band is fully developed at θ ⪸ 4 ML . Upon annealing of 5–100 ML deposits at temperatures above 750°C, XPS and UPS testify the completion of WSi2 formation and LEED patterns indicate an epitaxial overlayer.