Aperture-SNOM

Scanning near-field optical microscopy (SNOM) or near-field scanning optical microscopy (NSOM) Shear force microscopy (ShFM) Aperture SNOM (ASNOM) - Transmission ASNOM (T-ASNOM)... 

Scanning Near-Field Optical Microscopy (SNOM) Aperture SNOM (ASNOM) Collection ASNOM (C-ASNOM) Emission ASNOM (E-ASNOM) Evanescent Field SNOM (EF-SNOM) Nonaperture ASNOM (NA-SNOM) Shear Force Microscopy Transmission Mode (TSNOM) Reflection Mode Luminescence Mode... 

Figure 15.1 Schematic drawings of different SNOM methods, (a) Aperture SNOM (a-SNOM) (b) Tip-enhanced Raman spectroscopy (c) Scattering SNOM (s-SNOM).

Figure 15.7 Aperture SNOM IR images of a 8pm/8pm line/ space pattern obtained by mask-assisted deep-UV exposure of a 1 pm-thick photoresist layer. The images were collected at 2.80pm (a) and 2.94pm (b). IR absorption at the OH stretching vibration frequency at 2.94pm leads to the dark contrast of the exposed regions in (b). Reprinted with permission from Ref [50].

With an aperture SNOM, the situation should be similar. Given a clean, metal-free aperture with a diameter on the order of A/4 surrounded by a 100-nm thick aluminum annulus, one expects an almost unperturbed lifetime if the molecule is sitting below the center of the aperture, since the molecule is essentially embedded between two dielectric media, which are the glass core of the probe and the sample. When the tip is moved toward the side, the fluorescence is quenched when the metal is very close to the molecule. 

Figure 6. Triangular aperture SNOM probe excited with two different polarization states. With polarization shown on the left side two maxima of the electric field occur. Rotating the polarization by 90 degrees virtually only one maximum occurs [7]. 

The SNOM combines the possibilities of AFM and optical microscopy. On the one hand, it allows for probing of the surface and obtaining information on the topography. On the other hand, in aperture SNOM, the probe contains an aperture, and the sample can be illuminated locally (Fig. 5). The diameter of the aperture at the end of the probe is typically of the order of 50-100 nanometer, and therefore, the illuminating spot is not diffraction limited. Both transmission and tluorescence in combination with polarization provide appropriate contrast mechanisms. 

As aperture SNOM is amply described in Ref. 1 and, as the scattered SNOM techniques with modulation are also not very useful for the present topics, their elaborate equipment are not repeated here. However, the versatile reflection-back-to-the-fiber SNOM is simply a shear-force AFM with an optical addition. Figure 3 depicts a block diagram. ... 

Shear force microscopy (ShFM) Aperture SNOM (ASNOM)... 

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