Near-Field Microscopy Techniques
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While force interactions are most commonly employed for probing, manipulation, and addressing of nanoscale features, dielectric contrast mechanisms are also potentially useful means of probing nanostructures. Optical absorption or emission, dielectric contrast in the infrared (IR), far-infrared (FIR), or microwave regime are all part of a rich pool of phenomena observable with electromagnetic interactions, with applications in nanoelectronics, spintronics, and biotechnology being developed. To attain the highest resolution, it is necessary to confine the area in which the probing field interacts with the sample to subwavelength dimensions. This is accomplished by fabricating probes with subwavelength-sized features and scanning such near-field probes very close to the sample. This article summarizes such near-field techniques in the visible, IR, and microwave regime and relates them to current and future applications.