Due to their microphase separated morphology, block copolymers (BC) can exhibit photonic behavior if their domain periodicity is sufficiently large (>100 nm) . Classical spectroscopic characterization of these optical properties is routine, but only offers an ensemble picture of the materials behavior. Incorporation of these materials into optical devices, especially in the form of thin films where 2D in-plane photonic structure is possible, will require characterization which probes the optical properties associated with single microphase domains and defect structures.In anticipation of these needs, we apply Near-Field Scanning Optical Microscopy (NSOM) to the study of ultrahigh molecular weight photonic BC thin films. The sub-diffraction limit resolution of NSOM (=50 nm) allows for the direct optical imaging of BC microphase morphology; providing insight into the local optical structure of thin film specimens. We present here the first such optical images of BC microphase separation, collected via transmission aperture NSOM and NSOM polarimetry. Effects of the various scanning and collection parameters as well as input-light polarization on the contrast and detail seen in these micrographs are discussed.
Citation: Measuring Local Optical Properties: Near-Field Polarimetry of Photonic Block Copolymer Morphology
Pub Type: Others
BC microphase, block copolymers, near-field scanning optical microscopy, NSOM, optical devices, photonic BC thin films, thin films