## 5 Applications of 3D-SNOM
### 3D Probing of Near-Fields of Nanostructures
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Author** & **Year** & **Ref.** & **Microscope Configuration** & **z-Axis** & **x-y Dimension** & **Illumination** \\  & & & **Scanned** & **(\(\upmu\)m\({}^{2}\))** & **Wavelength** \\ \hline [PERSON] & 2012 & [31] & 100 nm aperture & fixed † & 24 & 1.55 \(\upmu\)m \\ \hline [PERSON] & 2012 & [38] & Apertureless & fixed † & 4 & 9-10 \(\upmu\)m \\ \hline [PERSON] & 2012 & [54] & 80 nm aperture & 8 \(\upmu\)m & 50 & 532 nm \\ \hline [PERSON] & 2012 & [55] & Square hollow pyramid, 100 nm aperture & microns & 32 \(\upmu\)m line scan & 980 nm \\ \hline [PERSON] & 2013 & [11] & \begin{tabular}{c} Al coated pyramid, 100 nm aperture \\ \end{tabular} & 30 nm & 5 & 0.4–2 \(\upmu\)m \\ \hline [PERSON] & 2013 & [30] & 100 nm aperture & fixed † & 800 & 1.55 \(\upmu\)m \\ \hline [PERSON] & 2013 & [34] & 100 nm aperture & 10 \(\upmu\)m & 100 & 780 nm \\ \hline Amenabar & 2013 & [42] & FTIR, Au coated apertureless & fixed † & 1.2 & 4-14 \(\upmu\)m \\ \hline le Feber & 2014 & [29] & Al coated, 218 nm aperture & 380 nm & 1 & 1.57 \(\upmu\)m \\ \hline Denkova & 2014 & [33] & \
\begin{tabular}{c} Al coated hollow pyramid, \\ 90 nm aperture \\ \end{tabular} & fixed † & 1 & 0.4–2 \(\upmu\)m \\ \hline Westermeier & 2014 & [45] & FTIR, apertureless & fixed † & 180 & 907 nm \\ \hline Liu & 2014 & [56] & Infrared, apertureless & 0.4 \(\upmu\)m & 7.2 & 1.56 \(\upmu\)m \\ \hline Ouyang & 2015 & [28] & 80 nm aperture & 2 \(\upmu\)m & 4 & 532 nm \\ \hline Ikeda & 2015 & [41] & 20 nm apertureless & 150 nm & 1.5 & 633 nm \\ \hline Ezugwu & 2015 & [48] & 80 nm aperture & 2 \(\upmu\)m & 2.5 & 532 nm \\ \hline Li & 2015 & [50] & Si 10 nm apertureless & 100 nm & 0.15 & 633 nm \\ \hline Martinez-Marrades & 2016 & [49] &
\begin{tabular}{c} Square–based pyramid, 100 nm aperture \\ \end{tabular} & 2.7 \(\upmu\)m & 3.6 \(\upmu\)m line scan & 660 nm \\ \hline Bulat & 2016 & [57] & Optical fiber, 50 um aperture & fixed † & 1600 & 532 nm \\ \hline Klein & 2017 & [58] & Au coated, 150 nm aperture & 2 \(\upmu\)m & 10 & 663 nm \\ \hline \hline \end{tabular}  
* Thermal heating of probe and stage. † Scans in the _z-x_ or _z-y_ planes were not performed.  
\end{table} 
Table 1: _Cont._In addition to gold nanostructures, semi continuous films of copper nanoparticles have also been identified as components for optoelectronic devices to manipulate scattered light fields and were studied by multidimensional SNOM methods. Small metallic particles of appropriate shape and size can be used to generate large plasmonic field enhancements that may be useful for optoelectronic devices [59]. 3D spatial mapping of these nanoparticles in the near-field revealed new phenomena concerning light scattering by nano-objects. Radiation scattering from nanostructures may have several potential applications in optoelectronic devices: in addition to providing information about the size, shape, and location of nanoparticles in a film, 3D SNOM can be used to map scattered light fields in space. The properties, location, and intensity of scattered light fields are of paramount importance for controlling light scattering in optoelectronic devices such as solar cells, waveguides, and light emitting diodes. 3D SNOM can be used to map constructive and destructive interference of scattered light fields to help improve the design or optimize the efficiency of such devices. Figure 7 illustrates how 3D SNOM mapping could be combined with AFM to image arrays of thermally nucleated copper nanoparticles obtained using an aperture tip [48]. The AFM image in shown in panel (a) was collected simultaneously with the SNOM image shown in panel (b) Yellow  
Figure 6: AFM (left) and SNOM (right) images of Au nanoparticles embedded in polyimide. (**a**) Annealing at 150 \({}^{\circ}\)C in an oxygen deficient environment creates large micron sized particles.