A focused beam of electrons in coincidence with a high current density Ar+sputtering beam and SIMS detection has been used to perform accurate depth profiling analyses of sodium in SiO2films. Conditions for exact charge compensation are described, and analyses of a 150‐keV sodium implant in a 0.73‐&mgr;m film of SiO2are presented. Without charge neutralization, 98% of the implanted sodium moved to the SiO2/Si interface during SIMS analysis, whereas optimum charge compensation resulted in a basically unaltered implant profile with only 0.06% sodium at the interface.