UNMONOCHROMATIZED SYNCHROTRON RADIATION PROMOTED SILICON OXYNITRIDATION AT ROOM-TEMPERATURE

We investigate the effect of unmonochromatized synchrotron radiation (USR) on the room-temperature reaction between a Si(111)2 x 1 surface and adsorbed NO. After exposition to NO of the Si(111) surface, an oxynitride/silicon interface is formed. The evolution with irradiation time of the oxynitridation of silicon and of the oxynitride/silicon interface formation is examined in situ by means of core-level and valence-band photoemission spectroscopy, Auger electron spectroscopy, and work-function measurements. The analysis of the valence band and Si 2p, O 2s, and N 2s photoelectron spectra, together with the Auger Si transition, clearly exhibits additional oxynitride formation under USR. The oxygen-to-nitrogen ratio, O/N, from the thin oxynitride layer increased after a long time (> 10 min) of exposure to USR. Hence, USR appears to have the opposite effect to the one produced by thermal activation in which the nitridation is favored.