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Application Note for Leica EM RES102 – Ion milling can be used to reduce the roughness of sample surfaces. Small angles less than 6° with respect to the sample surface are necessary. The high voltage depends on the material to be prepared. The reason for the levelling effect is the different milling angle of flat and rough surface areas. The milling rate is lower for small angles. The rough surface area will be faster milled. Ion polishing is often the final step of sample preparation. The prerequisite is a perfect mechanical prepreparation as samples with deep surface scratches cannot be ion polished. Soft materials usually have a smeared sample surface after mechanical polishing. It is necessary to remove this smeared material before ion polishing. Otherwise the above mentioned polishing effect does not work.