In situ ion beam analysis for swift heavy ion track characterisation

The damage which is produced when a swift heavy ion passes through solid material is called an ion track. Its cylindrical shape originates from the long range of the penetrating ion while at the same time the ion induced damage remains localized close to the ion trajectory. Such nanoscale damage can be observed directly by means of TEM and AFM, but there are also number of other techniques that can be used to characterize ion tracks indirectly. One of the most utilised techniques for indirect measurement of ion tracks is RBS/channelling. However, this ion beam analysis (IBA) technique is not available at large ion accelerator facilities where ion track studies are mostly done. Recent commissioning of the dual ion beam chamber at the RBI, Zagreb opens up an opportunity to study kinetics of ion track formation using in-situ RBS/c. Ion track formation is accomplished using swift heavy ions delivered by the 6 MV EN Tandem Van de Graaff accelerator, while simultaneously RBS/c measurement is done using proton beams delivered from the 1 MV Tandetron. This approach is especially important for studies close to the ion track formation threshold, where deviations from simple overlap track models are expected. To accomplish this, a substantial amount of experimental data is needed for reliable analysis and this novel approach provides adequate solution to this challenge. Another approach for in-situ IBA is to use swift heavy ions for simultaneous material modification and monitoring using ERDA. As shown recently, monitoring elemental changes in the sample, ion track characterisation can be accomplished. We present two applications of ERDA: a) monitoring stoichiometry changes during ion track formation in GaN and b) hydrogen loss in amorphous Al2O3 thin films.