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Advanced Imaging Magazine

Updated: January 12th, 2011 10:01 AM CDT

Don't Sweat the Small Stuff: See It

New nano-imaging techniques provide sub-wavelength spatial resolution images for applications like electronics and biomedicine
nanotechnology  image
Cornell University
nanotechnology  image
Cornell University
Figure 2
© Cornell University
Figure 2: 650 eV-wide electron energy-loss spectra captured at each pixel produced this spectroscopic image of a lanthanum strontium manganate and strontium titanate (La0.7Sr0.3MnO3/SrTiO3) multilayer, showing the different chemical sublattices (from top, left to right): the lanthanum-manganese edge, the titanium-lanthanum edge, the manganese-lanthanum edge, and a false-color image formed by combining the rescaled Mn, La, and Ti images.
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By Kristin Lewotsky

They tested the system on a perovskite multilayer structure of lanthanum strontium manganate and strontium titanate (La0.7Sr0.3MnO3/Sr
TiO3). The image shows five unit cells of the multilayer structure, providing information on how ordering and diffusion at the atomic scale can impact the macroscopic properties of materials (see figure 2). In tests, the system captured atomic level images in a matter of 30 to 40 seconds.

NANOTECHNOLOGY PRODUCES NANOIMAGES

In some cases, nanotechnology itself is helping with nano imaging. A quasi-periodic array of nanoholes in a metal screen can mimic the focusing effects of a high-numerical-aperture lens, say collaborators from the University of Southampton and Rutherford Appleton Laboratory. Capable of achieving sub-wavelength resolutions, the array produces one-to-one images of both coherent and incoherent point sources located within a few tens of wavelengths of the array. The lensing effect can be explained by the fact that the field of the array is reconstructed in the diffraction zone.

The 80 80 array of periodically spaced holes initially used created a pattern of diffracted orders so dense that individual orders/images could not be resolved. The group's solution was to use a Penrose array with 10-fold symmetry, which created a more widely distributed pattern. The array consists of 200-nm square holes separated by 1.2 m or more for a total size of 200 200 m2.

The group tested it with a point source positioned 11 m away from the grating. Using a coherent source at 660 nm, they produced 380-nm foci for a field of view as large as 20 m. For a smaller field of view, the best resolution was 200 nm. These results are equivalent to a conventional lens with an NA of 0.85; for coherent sources, the results correspond to an NA of 0.89.



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