Low-angle cross sections are produced inside an Auger microprobe using the equipped depth pro. le ion sputter gun. Simply the sample is partly covered by a mask. Utilizing the edge of this mask the sample is sputtered with ions. Due to the shading of the mask a cross section is produced in the sample. The slope of this cross section is considerably shallower than given by the geometrical setup. This is attributed to self-alignment effects, which are due to missing sputter cascades in the transition area between sputtered and shaded sample regions and a chamfering of the mask edge. These self-alignment effects are studied here using a 104.6 nm thick SiO2 layer thermally grown on a Si substrate. In this study on one hand for a fixed ion impact angle of 15.8 degrees as function of the sputter time several in situ low-angle cross sections were produced. This way slope angles between an ultimate low slope angle of 0.014 degrees and 0.085 degrees were achieved. On the other hand for a fixed sputter time the ion impact angle was varied between 14.8 degrees and 70.8 degrees. For these samples cross section slope angles between 0.031 degrees and 0.32 degrees are observed. These results demonstrate the distinct slope flatting of in situ cross sectioning. (C) 2009 Elsevier B.V. All rights reserved.