Abstract :
Asymmetric PS–b-PEO block copolymer exhibits well-ordered cylindrical morphology with nanoscale domain sizes due to
microphase separation. Since the PS and PEO blocks have large stiffness difference, this polymer system represents an ideal
candidate for studies of the phase contrast behavior in atomic force microscopy (AFM). In this paper, PS–b-PEO films are
investigated under different scanning conditions using two different atomic force microscopes. It is found that the phase contrast
of the film can be well described in terms of energy dissipation, though the exact phase image may also depend on the scanning
parameters (e.g., the repulsive versus attractive regimes) as well as the settings of the microscope. Height variation on sample
surface does not have significant effect on phase contrast. However, in order to obtain true topography of the polymer film, care
has to be taken to avoid damage to the sample by AFM. Under certain conditions, true topography can be obtained during the first
scan in spite of the surface-damaging forces are used.
