Block copolymer monolayer structure measured with scanning force microscopy moire patterns

We demonstrate that an analytical model can be used to interpret moire patterns in scanning force microscopy images of spherical domain block copolymer films, yielding grain orientations and a more than 10-fold increase in scan size without requiring a tedious empirical calibration. Moire patterns are the product of interference between two overlapping regular gratings and are sensitive to the grating periodicity and alignment. We apply this technique to SFM of a monolayer of a spherical domain block copolymer, where the SFM scan lines act as a reference grating, and the close-packed rows of the block copolymer domains form the sample grating. The block copolymer grain orientation and size are calculated from the moire patterns using an analytical model. The accuracy of the model is confirmed by directly imaging the block copolymer lattice with high-resolution SFM. Furthermore, we investigate the moire patterns of defects in this two-dimensional array of domains and demonstrate that dislocations can be reliably imaged depending on the pitch of the moire fringes and the orientation of the Burgers vector of the dislocations.