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Articles you may be interested inSpatial mapping of ordered and disordered domains of GaInP by nearfield scanning optical microscopy and scanning capacitance microscopy Patterned selfassembled monolayers of ferrocene and methyl terminated alkanethiols on gold: A combined electrochemical, scanning probe microscopy, and surface science studyWe have designed and demonstrated two simple and versatile reflection mode near-field scanning optical microscopes ͑NSOMs͒. In one scanner far-field collection is coaxial with the NSOM tip, and in the other scanner, the far-field collection is at a 45°angle to the NSOM tip. We quantitatively compare images obtained with the two scanners. While off-axis collection offers a significantly higher signal-to-noise ratio, it also introduces tip shadowing in samples with topographic features larger than approximately 40 nm. The additional contrast from the shadowing further complicates image interpretation and must be considered when performing NSOM in reflection with off-axis collection. In addition, we discuss some general issues that should be considered when designing a reflection NSOM.

Spatial hole burning near-field scanning optical microscopy ͑SHB-NSOM͒ is used to locally photopattern three species of organic thin films, poly͑2-methoxy, 5-͑2Ј-ethyl hexyloxy͒p-phenylene vinylene͒ ͑MEH-PPV͒, tris-8-hydroxyquinoline aluminum (Alq 3 ) 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-NSOM͒. 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.