It was recalled that the detection of Na in insulating samples by means of time-of-flight-secondary ion mass spectrometry depth-profiling had always been a challenge. In particular the use of O2+ as the sputtering species produced a troublesome artefact in the Na depth distribution, due to Na migration under the influence of an internal electrical field. Here, the influence of the sample temperature upon this artefact was addressed. It was shown that the Na transport was a dynamic process in accord with the advancing sputter front. Low temperatures mitigated the migration process by reducing the Na mobility in the target. In this work, two sample types were investigated. One was a Na-doped PMMA layer, deposited onto a thin SiO2 film, where the incorporation behavior of Na into SiO2 during depth-profiling was demonstrated. The other involved Na which was implanted into a thin SiO2 film. In this sample type, the migration behavior could be examined when defects - originating from the implantation process - were present in the SiO2 target. An approach was also proposed for the evaluation of an implanted Na profile which was unaffected by the migration process.

On the Temperature Dependence of Na Migration in Thin SiO2 Films during ToF-SIMS O2+ Depth Profiling. S.Krivec, T.Detzel, M.Buchmayr, H.Hutter: Applied Surface Science, 2010, 257[1], 25-32