Hi everyone,
We need to detect the nanoscaled geometric defects of a dense cylinder array using optical methods. However, the period of the array is so small that only 0th diffractive light exist via the bright field microscopy, making it difficult to get any information except the contrast. The nanoscaled defects are submerged by the contrast, since the intensity of the array is nearly consistent.
Well, is there any other optical method valid for distinguish the geometric information of a dense periodic array?
Individual, luminescent point defects in solids, so-called color centers, are atomic-sized
quantum systems enabling sensing and imaging with nanoscale spatial resolution. In this overview,
we introduce nanoscale sensing based on individual nitrogen vacancy (NV) centers in diamond. We
discuss two central challenges of the field: first, the creation of highly-coherent, shallow NV centers
less than 10 nm below the surface of a single-crystal diamond; second, the fabrication of tip-like
photonic nanostructures that enable efficient fluorescence collection and can be used for scanning
probe imaging based on color centers with nanoscale resolution.
Renju Peng , it is difficult to answer your question without knowing details of your sample, but you can try at first dark field microscopy; another way - microscopy with differential phase contrast. In general, you should try to see your defects by distinguishing between scattering properties of your defects and periodic array scatterers. Light scattering of nanosized defects is measurable quantity.
Valeriy Sterligov, thanks for your anwser. The sample is a cylinder array with a period of 100nm
Renju Peng , scattering of the incident light will be different by area of regular cylinders and area with a defect. Scattering by non-defect area will produce some given space distribution of such intensity, but partial scattered waves by defect will be different because the presence of defect will change the phase of scattered light. This phase modulation will produce scattered light. Here it is not important that the size of the defect is the smaller or much smaller relatively light wavelength. It is known experiments when was observed light scattered by a single atom in vacuum or monoatomic steps on the surface of a crystal (see, for example, our old article: Article Atomic structure display of a real silicon surface under lig...
).What is critical for such observation is the level of scatted light by non-defect areas. If its value is sufficiently low, if your non-defect zones are good optical quality in the above meaning, you will see your defects as point-like sources of scattered light, so you can estimate the amount, density, localization, and even kind of your defects.
Scatterometry of sub-wavelength periodic structures is a highly-developed technique that for the most part relies on zero'th order diffraction. At Zygo we have in past years developed interferometric scatterometers for some specialized applications; but there are many other designs. Just web search "scatterometry semiconductor" to get started.
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