The measured height of polystyrene nanoparticles varies with setpoint voltage during atomic force microscopy (AFM)
tapping-mode imaging. Nanoparticle height was strongly influenced by the magnitude of the deformation caused by the
AFM tapping forces, which was determined by the setpoint voltage. This influence quantity was studied by controlling
the operational AFM setpoint voltage. A test sample consisting of well-dispersed 60-nm polystyrene and gold
nanoparticles co-adsorbed on poly-l-lysine-coated mica was studied in this research. Gold nanoparticles have not only
better mechanical property than polystyrene nanoparticles, but also obvious facets in AFM phase image. By using this
sample of mixed nanoparticles, it allows us to confirm that the deformation resulted from the effect of setpoint voltage,
not noise. In tapping mode, the deformation of polystyrene nanoparticles increased with decreasing setpoint voltage.
Similar behavior was observed with both open loop and closed loop AFM instruments.