Effect of residual oxygen in Si(1 1 1)-7 × 7 surface on Si+ and Si2+ sputter yields

Abstract Effect of the residual oxygen impurity on the secondary ion yields in the sputtering from the Si(1 1 1)-7 × 7 surface bombarded by the 11 keV Ar 0 neutral beam has been studied with use of a time-of-flight technique. Even if the oxygen concentration is much less than the detection limit of the present Auger electron spectrometer, not only Si + and Si 2+ ions but also SiO + and SiO 2 + ions have been significantly detected. As the oxygen ion yield, estimated from SiO + and SiO 2 + signals, increases, the Si + yield is enhanced, whereas the Si 2+ yield is reduced. The enhancement of the Si + yield may be ascribed to the large electron affinity of O in comparison to that of Si, while the decrease in the Si 2+ yield could be explained in terms of the inter-atomic Auger transition between O and one of the precursors for Si 2+ (viz. an excited Si + with a 2p hole, Si +∗ ), which efficiently interferes with the production of Si 2+ .