Tracking femtosecond laser induced interactions in materials via real-time Ion Beam Analysis

The response of heteromaterials (e.g. bilayers, embedded nanoparticles in a matrix, or metal/semiconductor junctions) to thermal activation has been the subject of scientific research for a long time. Typical approaches to supply thermal energy include classical annealing (close to thermal equilibrium) and laser annealing (with extremely fast heating and quenching rates, hence out of equilibrium). The latter technique often results in metastable phases, since the fast cooling rate does not allow the system to reach thermodynamic equilibrium. Important parameters during laser annealing are the average energy per pulse, the pulse duration, pulse separation and repetition rate. Within the scope of this project, we will follow the laser-induced reaction in real time by ion beam analysis. To this end, we will set up in situ laser irradiation in the real time Rutherford backscattering spectrometry (RBS) chamber of the new Tandetron accelerator at iThemba. By collecting RBS spectra every 30 seconds while the sample is laser irradiated, we will be able to follow the response of the system “live”. Two classes of materials will be investigated: (i) NiTi and PtMo metallic bilayers and (ii) metal layers that react with a Si, Ge or GeSn substrate. Besides, we will set up real time channeling facility, which will allow us to follow phase separation of GeSn in situ.