Near-field scanning optical microscopy of nanostructures

Abstract

The applications of near-field scanning optical microscopy (NSOM) to various nanostructured materials are reviewed. The review begins with a description of experimental aspects of NSOM and the various contrast mechanisms available with the technique. Applications of NSOM to a variety of different materials are then addressed including: NSOM of semiconductor heterostructures, NSOM of polymers and molecular crystals, and NSOM of Langmuir-Blodgett films and layered organic self-assemblies.

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

“…We do not believe the scattering would account for such a large diameter of the dark spot since most of the light is confined to and is absorbed within one aperture diameter due to the highly localized nature of the evanescent near-field radiation. 38 It is apparent that the large width of the photo-oxidation hole at longer times is primarily due to the effect of saturating the photo-oxidation directly under the excitation source. It is also possible that the photo-oxidation process itself, which alters both the chemical identity of the polymer film as well as its morphology, influences the shape of the photo-oxidation hole.…”

“…As mentioned earlier, we have observed changes in MEH-PPV fluorescence spectra in oxygenated air which are more pronounced than when the sample was scanned in nitrogen. 38 Both oxygen which has diffused into the sample bulk and oxygen present in the air can react with MEH-PPV to form carbonyl groups. In both cases, triplet oxygen present in the film may contribute to the observed energy migration in MEH-PPV films.…”

Direct Photocurrent Mapping of Organic Solar Cells Using a Near-Field Scanning Optical Microscope

“…Shear-force or traditional AFM feedback modes are used to keep the tip within 10 nm of the surface, and the sample is always illuminated in the nearfield, thus allowing the optical properties of the surface to be probed with a resolution better than the diffraction limit of the probing light. 10 As such, NSOM provides 2D maps of both optical and topographic information simultaneously, and by operating in different detection modes, the absorption, fluorescence, and reflection properties of surfaces can be probed with a resolution of 50 to 500 nm. 10 NSOM has been used to probe the optical properties of conjugated polymers [11][12][13][14][15] and polymer blends.…”

“…10 As such, NSOM provides 2D maps of both optical and topographic information simultaneously, and by operating in different detection modes, the absorption, fluorescence, and reflection properties of surfaces can be probed with a resolution of 50 to 500 nm. 10 NSOM has been used to probe the optical properties of conjugated polymers [11][12][13][14][15] and polymer blends. 16,17 Fluorescence mapping of certain polymer blends in particular has been successful in allowing for the identification of the composition of the different phases.…”

Emerging Techniques in Polymer Microscopy

“…Applications that have been reviewed include Langmuir-Blodgett films [171], photosensitizers in liquid crystal polymers [172], liquid crystal polymer dynamics [173], orient ation in polyeth ylene single crystals [174], phase separation in polymeric light emitting diodes [175,176], dendrite materials [177], and nonlinear optical polymers [178]. The polarized NSOM can also be used to study molecular orientation with single-crystal polymers.…”