Optical anisotropy studies of silver nanowire/polymer composite films with Mueller matrix ellipsometry

Abstract

Silver nanowire (AgNW)/photosensitive polymer composite film fabricated by roll-to-roll die coating exhibits optical and electrical anisotropy, depending on the coating conditions. To clarify the relation between the optical anisotropy, the electrical anisotropy and the orientation of AgNWs, the orthogonal optical constants of the composite films were determined by Mueller matrix spectroscopic ellipsometry. Multiple-sample analysis of reflection mode Mueller matrix and polarized transmission data was performed assuming a three-layer model consisting of substrate/polymer layer/conductive layer. The effective optical constants of the conductive layer revealed that the localized surface plasmon resonances, which arise from electric oscillation of along the short axis of AgNW, are large in the crosswise direction where the sheet resistance is large. On the other hand, the surface plasmon resonance associated with the electric oscillation along the long axis of the AgNW is large in the lengthwise direction where the sheet resistance is small. It seems the optical and electrical anisotropy reflects the morphology of the composite film, where the long axis of AgNW is preferably oriented in the direction lengthwise to the coated film.