Ion beam processing with an ultra-low energy Ar+ micro-polisher: From fundamental understanding to process optimisation

Ion beam processes are used in many applications, including surface patterning, milling, implantation, sample characterisation and sample preparation for electron microscopy. The use of ultra-low energies in the sub-keV range allows to reduce the implantation depth of the ion species, and hence to reduce the irradiation induced damage in the sample. In the current study we explore the potential of a simple experimental setup for ultra-low energy ion beam processes in the impact energy range of 50 eV to 500 eV and pay attention to the ion-beam induced processes on the sample surface. Our work shows that when ion beam process related to milling need to be well controlled, ion beam induced deposition of residual gas molecules in the instrument chamber needs to be considered. Depending on ion energy and irradiation density, ion induced sputtering and deposition can compete. Hence, the quality of the vacuum can significantly impact the process. Experimental sputtering yields were difficult to obtain, therefore reference values for a large range of angles and energies were simulated.