Simplest method of measuring nanoparticles’ size and size distribution on the surface and on sub-surface layers

Simplest method of measuring nanoparticles’ size and size distribution on the surface and on sub-surface layers

Recently there has been an emphasis for characterizing nanostructured materials such as twodimensional (2D) and zero-dimensional (0D) materials. For example, graphene, carbon nanotubes, etc. are two-dimensional (2D) materials. Quantum dots (QDs) [1] is an example of a zero-dimensional (0D) material because the nano particles of the QDs do not form a network; instead they remain by themselves. See ref [2] for a review of 0D, 1D, etc. materials.

While synthesis of these nanomaterials has enjoyed success, however, characterizing various structural properties of these materials still face significant challenge. In this review, we describe a method for measuring the size and size distribution of nanoparticles via terahertz imaging technique. Reconstructive imaging via terahertz reflectometry has been described [1] where subnanometer resolution was demonstrated by a nanoscanner and a gridding algorithm.

ARP’s terahertz nanoscanner offers a straightforward means for characterizing nanoparticles for their size parameter and size distribution. A step-by-step outline is given herein.

  • Mount the sample on the nanoscanner. Here an 8” wafer is mounted; however, samples may be of any size or shape.
  • Conduct the scanning over a suitable area or volume. Minimum scan able area for the current setup is 1µm2or a volume of 1µm3. The scanning resolution ranges from a few hundred microns down to ~25 nm, in all three orthogonal directions (see Fig. 2). Appropriate scanning routine should be chosen either for Cartesian coordinates or for imaging curved surfaces and/or cylindrical volumes.
  • Convert the rasterized data to image via reconstructive imaging algorithm with provided software program; see Fig. 3 (a) for rasterized data and 3 (b) for a reconstructive image of the same data. The inverse gridding algorithm is described in details in ref. [1].
  • View a 3D image (if applicable) and also you may want to examine different layers one at a time
  • Extract a single layer of interest from the 3D image as shown in Fig. 5. You may want to render the image in greyscale for digitizing; however, greyscale is not mandatory for simple particle size analysis
  • Analyze the image for individual particle’s size measurement or for particle size distribution.

For more details and for questions/comments, contact: Anis Rahman, PhD Phone: +1-717-623-8201 email:

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