SNOM Structuring

More recently, the method of scanning near-field optical microscopy (SNOM) has been applied to LB films of phospholipids and has revealed submicron-domain structures [55-59]. The method involves scanning a fiber-optic tip over a surface in much the same way an AFM tip is scanned over a surface. In principle, other optical experiments could be combined with the SNOM, snch as resonance energy transfer, time-resolved flnorescence, and surface plasmon resonance. It is likely that spectroscopic investigation of snbmicron domains in LB films nsing these principles will be pnrsned extensively. 

Fig. 34. dPS volume fraction (J)dPS vs depth z for a 50/50 dPS/PBrxS mixture after annealing for different times at T=180 °C as revealed by TOF-FRES a tA=10 min, b tA=160 min, c tA= 6175 min). In the bottom part, a sketch of the domain structure is shown as revealed from the ion beam and scanning near field optical microscopy (SNOM) results (shaded areas dPS-rich domains white areas dPS-poor domains). From Straub et al. [153]... 

Instead of SNOM, in many cases, particularly if the sample is to be screened for Raman active spots and their spatial distance is more than half of the wavelength of the laser, it is also confocal Raman microscopy that delivers enough morphological and spectral information on both nanoparticle structure and SERS activity, respectively. Thus, confocal Raman microscopy is interesting for a wide variety of applications in biology, medicine, and technological materials research. 

Subsurface structures in silicon were also studied using apertureless s-SNOM in the IR range. Lahrech et al. have shown successfully that implanted boron lines in silicon can be detected with a lateral resolution of -400 mn, even in the absence of any topographical contrast [47]. Knoll and Keilmann have performed near-field... 

Akhremitchev et al. presented a set-up based on the same principle, namely 1R s-SNOM with a side-illuminated AFM tip, and employed it to characterize nano-structured polymer blends that were used as minimally adhesive surface coatings to prevent biofouHng [57, 58]. Raschke ct al. used sharp Au-coated, forward-pointing ( nose-type ) AFM probes with a radius of 10-15 nm, and obtained fixed-... 

In the following chapters both worlds (the present micro- and the future nano-world) are shown, from the perspective of lateral structures using laser ablation and/or the specially designed polymers. Selected examples/applica-tions of microstructures (diffractive gratings, Fresnel lenses) and possible future writing techniques (AFM and SNOM) are presented. 

Nanostructuring of designed polymers and of a model compound was achieved by light force (SNOM) and mechanical manipulation (AFM). The latter process was carried out in combination with low-fluence laser irradiation to activate (soften) the polymer for mechanical structuring. 

There are a number of excellent reviews on SNOM and its applications in the study of organic materials.The reader is referred to these reports for detailed information on the technique and some of its applications. We focus on some of our results on the use of SNOM for illustrating its usefulness in the study of supramolecular structures. 

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