Probing nanoscale photo-oxidation in organic films using spatial hole burning near-field scanning optical microscopy

• Published in: The Journal of chemical physics 2000-05, Vol.112 (18), p.7864-7872
• Main Authors: Credo, G. M., Lowman, G. M., DeAro, J. A., Carson, P. J., Winn, D. L., Buratto, S. K.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.481391

Spatial hole burning near-field scanning optical microscopy (SHB–NSOM) is used to locally photopattern three species of organic thin films, poly(2-methoxy, 5-(2′-ethyl hexyloxy)–p-phenylene vinylene) (MEH–PPV), tris-8-hydroxyquinoline aluminum (Alq3) and dye-functionalized polyelectrolyte self-assembled layers, on a 100 nm length scale. In SHB–NSOM the film is illuminated with light from a stationary NSOM tip to induce photo-oxidation. The reduction in the fluorescence yield resulting from this exposure is then mapped using fluorescence NSOM (FL–NSOM). We have examined the localized photo-oxidation as a function of time, position, and environment free from the limits of far-field spatial averaging. In all of the thin film materials studied we find that the long-time diameter of the dark spot is much larger than the tip diameter and is a signature of energy migration. Characteristic lengths of the energy migration are extracted from this data by a simple diffusion model and are found to be of the order of a few hundred nanometers for each of the films studied.