Nanometer‐scale roughness study and indentation test with a scanning tunneling microscope

The surface roughness of four gold surfaces mechanically finished, three by diamond cutting and one by mechanical polishing, were measured with a scanning tunneling microscope (STM) and with a conventional stylus profilometer. The roughness measurements revealed that the maximum height and the center line average of each profile varied with its representative wavelength. The relationship between roughness parameters and wavelength was almost linear on a logarithmic graph. The indentation tests were done on the best gold surface with a Pt STM probe tip. STM images and profile curves between, before, and after indentation were compared. Most of the valleys around the indentation point changed in depth after contact: some valleys became shallow and other became deep. The tip may become blunt during contact, but the variation of change in depth of valleys is not explained only by the damage of the tip.