Surface recession of silicon under normally incident oxygen bombardment studied by atomic force microscopy of microscale sputtered craters

Transient phenomena in surface recession of silicon were investigated using a finely focused, normally incident 12 keV O2+ beam rastered over 8 µm wide squares. The depth of the sputtered craters was determined by atomic force microscopy. A linear depth–fluence relation was observed above ∼2.2 × 1017 O atoms cm−2. The crater depth offset was found to be −2.6 ± 0.5 nm. This is significantly smaller than the offset of −4.3 nm predicted by an analytical sputtering–oxidation model (ASOM). The original version of the model involved the assumption that the decrease in silicon removal rate is directly correlated with the total oxygen content of the sample. The present results support the idea that the changes in sputtering yield are proportional to the amount of oxygen accumulating at the receding surface in the form of SiO2. Evidence is also provided that the frequently used ISRD simulation code (predicted crater depth offset about −8 nm) needs further revisions.