Nanoscale oxidative patterning and manipulation of conjugated polymer thin films

Near-field scanning optical microscopy (NSOM) is used to modify the surface of thin films of poly[2-methoxy,5-(2ʹ-ethylhexoxy)-1, 4-phenylenevinylene] (MEH-PPV) with spatial resolution of 100 nm. Thin films were patterned using the NSOM tip with high power illumination (approaching 1 kW/cm2). This exposure results in both a reduction of the photoluminescence of the film and a change in the surface topography (a surface depression). By monitoring the broadening of the emission spectrum as a function of exposure time in ambient conditions and under flowing nitrogen, we confirm that the pattern is due to photo-oxidation. We have thoroughly examined the dependence of the depth of contrast, the size of the dark spot and the size of the surface depression on illumination power, energy migration and exposure time. In addition, we have created a number of patterns with features limited only by the size of the NSOM tip.