Morphology of PS-PEP diblock copolymer film – Tapping mode  aspect image of a polystyrene-block-poly(ethylenealt-propylene) (PS-PEP) film on a silicon wafer. The darker region on the left side with lower  aspect corresponds to the  towering side of a 16 nm step in the wafer. In this region and the darker curved region on the right, the film forms a PS wetting layer. In the lighter region with higher phase, the film contains a  unique layer of spherical PEP microdomains. Several  perpendicular rows of aligned microdomains are seen on the low side of the step. Diblock copolymers can self assemble into  complicated  fitful structures, a property that has attracted interest for their  spend as templates in nanolithography. Understanding how film thickness and step height  move domain location and orientation aids in developing  obscure copolymer templates. Imaged with the MFP-3D AFM; scan width 2 μm, Z (phase) scale 10°. Adapted from Ref. 5.