We found that a transient region of SIMS profiles was suppressed to less than the native oxide in silicon, with O-2(+) bombardment energy of less than 0.2 keV under an incident angle of O degrees with respect to the surface normal without oxygen flooding. However, gallium segregated significantly due to oxidation caused by O-2(+) bombardment in this condition. We also found that the segregation decreased as the incident angle increased, and that it disappeared at the angle of around 40 degrees, which was verified by comparing SIMS profiles with the HR-RBS profile. These results suggested that the angle of around 40 degrees was the critical angle to prevent segregation. The transient region was almost the same at angles of 0-40 degrees. Therefore, we consider that the energy of 0.2 keV at the angle of around 40 degrees under O-2(+) bombardment without oxygen flooding is the optimum SIMS condition for depth pro. ling in the near-surface region. On the other hand, the profile shift of arsenic depending on the angle was quite different as compared with gallium, but the shift was a minimum at the same critical angle. We expect that more accurate profiles for other impurities can be obtained using this SIMS condition. (C) 2008 Elsevier B.V. All rights reserved.