Slumping of Hierarchically Patterned Thermoplastic Polymer Thin Films

Hierarchical patterning of thermoplastic polymer thin films can be achieved by layering nano and micro-scale patterns onto the films using nanoimprint lithography. This process creates conditions far from equilibrium, and residual stress remains within the patterned polymer. These stressed patterns are susceptible to “slumping”, a form of decay in which the height of the pattern and the sharpness of the features decrease. The slumping of the nanopattern in hierarchically patterned polystyrene (PS) films is expected to progress at a slower rate due to the stabilizing presence of the micropattern. Additionally, the phenomenon of slumping is expected to be governed by two separate driving forces: residual stress and diffusion. Atomic force microscopy (AFM) is used to measure the vertical pattern height differences after the films are exposed to temperatures higher than the glass transition temperature (Tg).