jpk-files contain the as-measured AFM data for the fresh Ni film as well as the Ni film after 1000 cycles, which is indicated in the file name. Images were created using the open source software Gwyddion. A polynomial background was subtracted from the as-measured data. The image was corrected for horizontal scars (strokes) using the respective feature in Gwyddion. The minimum data value was then defined as zero. Roughness information was obtained using the 'statistical quantities' feature in Gwyddion. 