Near-field scanning optical microscopy enables direct observation of Moiré effects at the nanometer scale

This work reports probing the Moiré effect directly at the nanometer scale via near-field scanning optical microscopy (NSOM). Periodic metal nanostructures of Au and Cu have been produced sequentially using particle lithography, and the overlapped regions serve as Moiré patterns at nanometer scale. The Moiré effect in these regions can be directly visualized from NSOM images, from which periodicity and structural details are accurately determined. In addition, the near-field Moiré effect was found to be very sensitive to structural changes, such as lateral displacement and/or rotations of the two basic arrays with respect to each other. Further, nanostructures of Cu exhibited higher photon transmission than Au from NSOM images. Collectively, NSOM enables direct visualization of the Moiré effect at nanoscale levels, from optical read out, and without enhancements or modification of the structures. The results demonstrate the feasibility to extend applications of the Moiré effect-based techniques to nanometer levels.