EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Nanostructuring of surfaces and subsequently tuning its properties is an important toolkit in nanoscience and surface physics. The formation of nano-hillocks and ion-tracks, induced by slow highly charged ions and swift heavy ions, respectively, were found to be mediated by a strong coupling of electronic excitations to lattice heating. In order to compare to previous results with slow highly charged ions, we utilize CaF2(111) surfaces as a model system. We present here a more direct way to trigger a nanomelting process by using Au-cluster ions at keV energies. These cluster impacts trigger surface melting on the nanoscale due to a high energy density converted into surface atom temperature by nuclear collisions. Subsequent expansion of a nanometric surface volume and rapid quenching leaves hillock structures similar to those observed by irradiation with slow highly charged ions. We show that not only comparable nano-hillocks can be obtained with cluster-irraditions but that the size can be fine-tuned by varying the cluster-size in the range of 1-10 atoms/cluster keeping the kinetic energy constant at 30 keV. Our results on the CaF2 model system pave the way to use slow cluster ion beams to tailor surfaces of materials not susceptible to highly charged or swift heavy ion impacts.