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Imaging tools for nanoscicence involving sub-100-nm scale objects have been dominated by atomic force
microscopy (AFM), scanning tunneling microscopy (STM), and electron microscopy (SEM, TEM). These imaging
techniques have contributed substantially to the development of nanoscience, providing a very powerful diagnostic tool
capable of obtaining images with atomic resolution or as a subsidiary mechanism to arrange or modify surfaces also at
the atomic scale [1,2]. However, some important problems have persisted traditional nanoscale imaging techniques. For
example when scanning a nanometer size object that is not attached rigidly to a surface the interaction with the tip
significantly perturbs the specimen degrading or eventually precluding the image acquisition. Electron microscopy often
requires surface preparation, consisting of metallization of the sample to avoid surface charging. Additionally the
metallization of the sample may alter its characteristics and also limits the resolution. In both cases, if the sample is large
(millimeters in size) due to the limited field of view, the image obtained with these conventional methods is only
representative of a very small portion of the object.
Wavelength-limited holographic imaging using carbon nanotubes as the test object with a table-top extreme
ultraviolet (EUV) laser operating at 46.9 nm will be discussed. The resolution achieved in this imaging is evaluated with
a rigorous correlation image analysis and confirmed with the conventional knife-edge test. The nano-holography
presented requires no optics or critical beam alignment; thus the hologram recording scheme is very simple and does not
need special sample preparation. In holography, image contrast requires absorption to provide scattering by the
illuminating beam. The EUV laser wavelength employed in this experiment (46.9nm) is advantageous because carbon
based materials typically exhibit very small attenuation lengths, around 25 nm. The high absorption of even small object
volumes produces high optical contrasts. The short attenuation length thus enables nearly full contrast for most objects
without applying forces to the imaged objects, no charge buildup, and without the need for complicated sample
preparation. Additionally this simple technique allows to image macroscopic size objects, several millimeters square
with arbitrary shape while simultaneously sustaining across the image sub-50 nm spatial resolution. This characteristic
is equivalent to storing data at a density rate of ~0.3 Tbit per square inch over large areas, and represents a simple
demonstration of a method that allows permanently dense storage of a large amount of data.
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