Near-field photoconductivity of stretch-oriented poly(para-phenylene vinylene)

Abstract

Near-field scanning optical microscopy (NSOM) with photoconductivity contrast is used to map the transport properties of stretch-oriented poly(p-phenylene vinylene) thin films on a 150 nm length scale. Near-field photoconductivity is highly sensitive to film morphology and contrast is observed even in films with uniform photoluminescence. Regions of relatively higher photocurrent signals are correlated to regions with higher molecular order which have contrast approaching 15%. In addition, the photocurrent signal decreases sharply as the near-field tip approaches the surface of the film while at the same time the photoluminescence signal increases. The sharp decrease is attributed to the perturbation of the applied electric field within the polymer film by the metal on the NSOM tip.