Energy transfer from fluorescent thin films to metals in near-field optical microscopy: Comparison between time-resolved and intensity measurements

The fluorescence intensity, fluorescence decay time, and shear-force images of a thin film have been simultaneously investigated by reflection scanning near-field optical microscopy using an uncoated fiber tip. The sample is made of a europium chelate embedded in a 32-nm thick polymer layer that coats a periodic structure of gold and chromium. It is contended that the three images carry different and somewhat complementary information; the shear force supplying the sample profile while the intensity mainly depends on the local sample’s reflectance. Moreover, the decay time exhibits the local-energy-transfer process that takes place between the metallic substrate and the dye layer.