Near-field microscopes

FIGURE 10.2 Concept of (a) aperture type and (b) apertureless type near-field microscopes (c) is the Fourier transform function of (a) and (b), which shows propagation and evanescent light components. 

In section IID, we introduced the utilization of chemical enhancement effect for higher sensitivity in TERS. Here, it should be pointed out that in addition to electromagnetic enhancement and chemical enhancement effects, physical deformation induced by tip-applied force showed extra enhancement effect in TERS on carbon materials such as SWNTs and fullerene molecules (Yano et al. 2005, 2006 Verma et al. 2006). This tip-pressurized effect is a unique feature of TERS and not observable in SERS. Since the spatial resolution of TERS with tip-pressurized effect is determined by the size of the very end of the metallic tip that has direct contact with the molecules, this is a very promising approach to improve the spatial resolution of the near-field microscope. 

Lessard, T. J., Lessard, G. A., and Quake, S. R. 2000. An apertureless near-field microscope for fluorescence imaging. Appl. Phys. Lett. 76 378-80. 

Furukawa H, Kawata S (1998) Local field enhancement with an apertureless near-field-microscope probe. Opt Commun 148 221... 

Ramanujam, P. S., Holme, N. C. R., and Hvilsted, S. Atomic force and optical near-field microscopic investigations of polarization holographic gratings in a liquid crystalline azobenzene side-chain polyester. Appl. Phys. Lett. 1996, 68, pp. 1329-1331. 

Muramatsu H, Homma K, Yamamoto N, Wang J, Sakata-Sogawa K, Shimamoto N. Imaging of DNA molecules by scanning near-field microscope. Materials Sci Eng C. 2000 12 29-32. 

Fig. 21. a) Schematic repiesentation of a scanning tip microwave near-field microscope for analyzing ferroelectric and dielectric libraries, b) Composition of a region of a BaTiOj ferroelectric library with dopands indicated, c) Image of tangent loss (tan 6) from this library obtained with the near-field scanning microwave microscope [174]. 

Near-field scanning optical microscopes (NSOM or SNOM) are mainly used in fluorescence and VIS measurements. They provide optical images with spatial resolution less than the Abbe s limit of Ajl. The high lateral resolution is commonly achieved by using the optical near-field, e. g. in close vicinity of a very narrow fiber tip. Figure 5.16 illustrates the design of a near-field microscope. 

Fig. 5.16 Scheme of a near-field microscope. Light emerges from a fiber tip with the diameter of the orifice below the refraction limit. The configuration shown employs near-field excita-tion/far-field detection. The alternative configuration is far-field excitation/near-field detection. 

R. Pomraenke, C. Ropers, J. Renard, C. Lienau, L. Lur, D. Polli, and G. Cerullo, Broadband optical near-field microscope for nanoscale absorption spectroscopy of organic materials. J. Microscopy Oxford, 229, 197 (2008). 

Fleischer, M., Stanciu, C., Stade, E, Stadler, J., Braun, K., Heeren, A., Haffner, M., Kern, D. P., and Meixner, A. J. (2008) Three-dimensional optical antennas Nanocones in an apertureless scanning near-field microscope, App/. Phys. Lett, 93,111114/1-3. 

Specht M, Pedarnig JD, Heckl M, and Hansch TW (1992) Scanning plasmon near-field microscope. Physical Review Letters 68 476-478. 

Fig. 9.11 Schematic drawing of a scanning plasmon near-field microscope. A STM tip modifies the propagation of surface plasmons on a thin siiver surface. Scanning of the tip resuits in a two-dimensional image of the surface. Reprinted with permission from Specht et al. (1992). Copyright 1992, American Physicai Society.

Pohl, D. (1982). Optical near-field microscope. European Patent Application No.Ol12401. 

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