F. Rochet et al., ETHYLENE ON SI(001)-2X1 AND SI(111)-7X7 - X-RAY PHOTOEMISSION SPECTROSCOPY WITH SYNCHROTRON-RADIATION, Physical review. B, Condensed matter, 58(16), 1998, pp. 11029-11042
The adsorption of ethylene on Si(001)-2 x 1 and Si(111)-7 x 7 has been
studied at 300 K using core-level (Si 2p, C Is) and valence-band x-ra
y photoemission with synchrotron radiation; Dangling bonds play a very
different role in the chemisorption process on these two surfaces. Wh
ile for Si(001)-2 x 1 the quenching of the surface states ''monitors''
the molecule uptake, this is not the case for Si(111)-7 x 7: the adso
rption process continues well after all surface states have disappeare
d, and carbon coverages greater than that deduced from the rest-atom/a
datom bridge model are obtained. An alternative model is proposed, in
which molecules are bonded directly to the rest plane. The thermal sta
bility of both surfaces covered by ethylene is also studied. We relate
the formation of carbon-rich layers at 820-860 K to the strong change
s in the electronic structure of the silicon surface. [S0163-1829(98)0
2840-9].